MX2008007587A - Ceramic metal halide lamp - Google Patents

Abstract

A metal halide lamp (10) includes a discharge vessel (12) which may be formed of a ceramic material. The vessel defines an interior space (16). An ionizable fill (17) is disposed in the interior space. The ionizable fill includes an inert gas, mercury, and a halide component. The halide component includes an alkali metal halide, an alkaline earth metal halide component, and optionally at least one of a rare earth halide and a Group HIA halide. The alkaline earth metal halide component includes at least one of a barium halide and a strontium halide. At least one electrode (18, 20) is positioned within the discharge vessel so as to energize the fill when an electric current is applied thereto. The lamp having a wall loading, when energized, which is sufficient to maintain an active tungsten halogen cycle.

Description

CERAMIC METAL HALIDE LAMP This application claims the benefit, as a continuation-in-part, of the serial request no. 1 1 / 040,990, filed January 21, 2005, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND The present invention relates to an electric lamp with high efficiency, good color visualization and high maintenance of lamp lumen. It finds particular application in relation to a ceramic metal halide lamp with barium or strontium halides in the filling and will be described with particular reference thereto. The discharge lamps produce light by ionizing a vapor filling material, such as a mixture of rare gases, metal halides and mercury with an electric arc passing between two electrodes. The electrodes and filler material are sealed inside a translucent or transparent discharge vessel, which maintains the pressure of the energized filling material and allows the emitted gas to pass through it. The filler material, also known as a "dose", emits a desired spectral energy distribution in response to being excised by the electric arc. For example, halides provide distributions of spectral energies that offer a wide choice of luminous properties, for example, chlorine temperatures, color displays and light efficiencies.

Ceramic metal halide lamps have been developed with efficiencies in the range of approximately 90-100 lumens per watt (LPW), Ra color display rates of 85-95, or greater, and lumen maintenance values of 80 %, or greater, and color temperatures of between approximately 2600 and 4000K in wall loads from approximately 20 to 50 W / cm2. However, premature failure of the lamps may occur due to darkening of the discharge receptacle walls. Darkening is due to tungsten transferred from the filament to the wall. It has been found that the presence of oxygen and / or water vapor in the lamp atmosphere contributes to wall darkening. Water vapor is particularly damaging because even trace amounts increase the evaporation of the tungsten filament coil through the well-known "water cycle". In the water cycle, the temperature of the tunsgene coil is thermally sufficient to decompose the water vapor into hydrogen and oxygen. The resulting oxygen reacts with the tungsten from the coil to form volatile oxides, which migrate to cold parts of the lamp and condense. These oxide deposits are reduced by gaseous hydrogen to produce black metallic tungsten and reformed water, which causes the cycle to repeat itself. Tungsten-halogen lamps, which comprise a hermetically sealed light-transmissive discharge vessel, enclosing a tungsten filament and containing a filler comprising a halide or halogen gas, are widely used in a variety of applications. Some of these lamps operate a tungsten-halogen cycle which is a continuous, regenerative process, in which a halogen-containing tungsten compound is produced when the halide is chemically combined with tungsten particles that evaporate from the incandescent tungsten filament . The subsequent thermal decomposition of these halogen-containing tungsten compounds thus formed in the filament, returns the tungsten particles back to the filament. The halogen compounds used for the filling include bromine and bromides, such as hydrogen bromide, methyl bromide, dibromethane and bromoform. Lamps operating at low wall loads (WL), for example, below about 30 W / cm2, and thus low temperatures, are to say below indoor wall temperatures of about 200 ° C., generally do not support the tungsten-halogen cycle. Additionally, if the WL is too low, then the halide temperature tends to be too low, leading to a reduced halide vapor pressure and reduced performance. It has been proposed to incorporate a calcium oxide or oxide of your ngstene dispenser into the discharge vessel, as described, for example, in WO 99/53522 and WO 99/53523 for Koninklijke Philips Electronics N .V. , US patent no. 6, 844, 676 for Alderman, et al. , describes an arc tube filling comprising metallic mercury, a mixture of noble gases and, optionally, radioactive 85Kr, and a salt mixture, such as a mixture composed of sodium iodide, calcium iodide, thallium iodide and several rare earth iodides. The exemplary embodiment provides a new and improved metal halide lamp, capable of operating at high or low power, which has high efficiency and good color visualization.

BRIEF DESCRIPTION In one aspect of the exemplary embodiment, a ceramic metal halide lamp includes a discharge vessel formed of a ceramic material, which defines an interior space. An ionizable filler is disposed in the interior space. The ionizable filler includes an inert gas, mercury and a halide component. The halide component includes an alkali metal halide, an alkaline earth metal halide component, and optionally at least one of a rare earth halide and a Group I IA halide. The alkaline earth metal halide component includes at least one of a barium halide and a strontium halide. At least one electrode is positioned within the discharge vessel, in order to energize the filling when an electric current is applied thereto. The lamp has a wall charge, when energized, which is sufficient to maintain the tungsten-halogen cycle. In another aspect, a ceramic metal halide lamp includes a discharge vessel formed of a ceramic material, which defines an interior space. An unstable filling is arranged in the interior space. The ionizable filler includes an inert gas, mercury and a halide component The halide component includes, expressed as% mol of the total halide component of the filler, at least about 5 mol% of sodium halide, optionally, from about 1% to about 10% of a metal halide. of group MIA, from about 10% to about 95% of an alkaline earth metal halide, the alkaline earth metal halide comprising at least one of barium halide and strontium halide, and optionally from about 1% up to about 1 5% of a rare earth metal halide The lamp has a wall load of at least 30 W / cm 2. In another aspect, a method of operating a lamp includes providing a discharge container with a spreadable filler comprising an inert gas , mercury and a halide component, the halide component comprises, expressed as% mole of the total halos content of the filling, at least about 5 mole% of sodium halide, optionally , from about 1% to about 10% of a group I MA metal halide, from about 10% to about 95% of an alkaline earth metal halide, the alkaline earth metal halide comprising at least one of the barium halide and strontium halide, and optionally from about 1% to about 15% of a rare earth metal halide The lamp is energized to generate a discharge and provide the discharge vessel with a wall load of at least 30%. W / cm2 One advantage of at least one embodiment is the provision of a ceramic arc tube fill with improved performance and lumen maintenance. Another advantage of at least one embodiment is in the improved maintenance of the halogen-tungsten cycle. Another advantage of at least one modality is in the ability to select color display properties of a lamp. Still additional advantages will be apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of preferred embodiments.

DRAWINGS FIGURE 1 is a perspective view of a lamp according to the exemplary embodiment, FIGURE 2 is a side sectional view of a first embodiment of an arc tube for the lamp of FIGURE 1, and FIGU FIG. RA 3 is a side sectional view of a second embodiment of an arc tube for the lamp of FIGURE 1 DETAILED DESCRIPTION A discharge lamp suitable for a variety of applications has a high efficiency, good color visualization and good maintenance of lamp lumen. The lamp is provided with a filling, which is formulated to handle the tungsten-halogen cycle time that enables improved color visualization filler includes mercury and an alkaline earth metal halide component comprising at least one and in some aspects, a combination of alkaline earth metal halides. The halides of alkaline earth metals can be selected from calcium halides (Ca), barium (Ba), magnesium (Mg) and strontium (Sr). Suitable halides include chlorides, iodides, bromides and combinations thereof. In several aspects, the lamp has a wall load of at least about 30 W / cm2. The wall load may be at least about 50 W / cm2, and in some embodiments, about 70 W / cm2, or greater. Below about 25-30 W / cm2, the arc tube walls tend to be too cold for maintaining the efficiency of the tungsten-halogen active cycle. Although the mechanism is not fully understood, it is proposed that the alkaline-earth metal halide component, in combination with the wall charge, maintain a tuntene active halogen wall cleaning cycle, which the tunstene evaporates from the Hot electrode tips are mainly deposited again on the colder parts of the electrodes instead of being deposited on the inner surfaces of the arc tube walls. With reference to FIGURE 1, a lighting assembly includes a metal halide discharge lamp 1 0. The lamp includes a discharge vessel or arc tube 1 2 having a wall 14 formed of a ceramic material or other suitable material, which encloses a discharge space 16. The discharge space contains a material lomotable filler 1 7 Electrodes 1 8, 20 extend across opposite ends 22, 24 of the arc tube and receive current from conductors 26, 28, which provide a potential difference through the arc tube and also support the arc tube 1 2 The arc tube 1 2 is surrounded by an outer bulb 30, which is provided with a lamp cover 32 at one end, through which the lamp is connected with an energy source 34, such as main voltage The lighting assembly also includes a ballast 36, which acts as an igniter when the lamp is turned on. The ballast is located in a circuit containing the lamp and the power source. The space between the arc tube and the bublo Outside can be evacuated Optionally, a cover (not shown) formed of quartz or other suitable material, surrounds or partially surrounds the arc tube to contain possible arc tube fragments in the event of a tube breakage of In operation, the electrodes 18, 20, produce an arc between the tips 38, 40 of the electrodes (FIG. 2), which ionizes the filling material to produce a plasma in the discharge space. the light produced are mainly dependent on the constituents of the filling material, the voltage across the electrodes, the temperature distribution of the chamber, the pressure in the chamber, and the geometry of the chamber. The electrode tips 38, 40 are separated by a distance d, which defines the arc gap. The ballast 36 is selected to provide sufficient power to the lamp to provide a wall load. at least about 30 W / cm2. As defined herein, the arc tube wall load (WL) = W / A, where W is the total arc tube energy in watts and A is the area in cm2 of the arc tube wall , which is located between the electrode tips 38, 40. For the illustrated lamp of FIGURE 2, where the arc tube walls are of uniform distance r from the axis XX of the lamp, A = 2prd. For more complex designs, where the walls are curved between the electrode tips, as illustrated for example, in FIGURE 3, the area can be determined by modeling techniques which consider the variation in r. The arc tube energy is the total arc tube energy including the electrode energy. For a ceramic metal halide lamp, the filler material may comprise a mixture of mercury, an inert gas, such as argon, krypton or xenon, and a halide component, which includes a halide alkaline earth metal component and may further include one or more alkali metal halides, such as sodium and cesium, one or more halides of a rare earth metal (RE) selected from scandium (Se), yttrium (Y), lanthanum (La), cerium (Ce), praseodimium (Pr ), neodymium (Nd), promised (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), tulio ™, ytterbium (Yb) and lutetium (Lu) and / or one or more metal halides selected from Group II IA of the periodic table of the elements, such as, indium (I n) and thallium (TI). The mercury dose can comprise approximately 3 up mg / cm 3 of the arc tube volume, for example, at least 5 mg / cm 3 of arc tube volume and in one embodiment, at least 10 mg / cm 3. In one embodiment, the dose of mercury is less than about 20 mg / cm 3 of arc tube volume. The mercury weight was adjusted to provide the desired arc tube operating voltage (Vop) to draw power from the selected ballast. In an alternative, the lamp filling is free of mercury. The halide dose may comprise from about 10 to about 50 mg / cm 3 of arc tube volume, i.e., a halide to mercury dose ratio of from about 1: 3 to about 1: 5: 1, expressed in weigh. Normally, the halide element is selected from chlorides, bromides and iodides. Iodides tend to provide greater lumen maintenance, since the corrosion of the arc tube is less than with comparable bromide or chloride. The halide compounds will usually represent stoichiometric ratios. The alkaline-earth metal halide (s) of the filler can have the general form MX2, where M is selected from Ca, Ba, Sr and Mg and X is selected from Cl, Br and I. In several aspects, the alkaline earth metal halide component includes at least one barium halide (BaX2). By selection of the alkaline earth metal halide or combination thereof, a color temperature appropriate for the desired use of the lamp can be generated. For example, a lamp which emits white light can be easily formulated by combining two or more of the alkaline earth metal halides, together with other components of the filler. The Barium halides, for example, tend to provide a red spectral performance, while magnesium, calcium and strontium have mainly green, red and blue, and blue spectral performances, respectively. In some embodiments, the alkaline-earth metal halide component includes BaX2 and one or more of SrX2 and CaX2. In a specific embodiment, the alkaline earth metal halide component includes BaX2 and SrX2. Exemplary halides include Bal2, Srl2, Ca2, Mg2, Nal, Ti1, Dyl3, Hol3, Tm3, Inl, Cel3, CeBr3, Ca2, and Csl, and combinations thereof. Expressed as mole fractions, the total halide component may comprise from about 5% to about 90% of an alkali metal halide, such as NaX, where X may be a halide or combination thereof, from about 10%, up to about 95% of the alkaline earth metal halide component MX2, from 0% to about 10% of a M group amino halide, such as TI halide or I n halide, and from 0% to about 1%. % of a rare earth metal halide. In several aspects, MX2 is at least about 15% and in one embodiment, MX2 is at least about 18%. In some aspects, MX2 is less than about 35%, and in some embodiments, less than about 30%. In several aspects, the group I halide IA is an IT halide. The group I halide IA can be at least 1% of the total halide component and in some aspects, it can be at least 2%. In some aspects, the group halide MIA is less than about 4%. The rare earth metal halide can be less 2% and in some aspects, less than 6% of the total halide component. The alkali metal halide may be at a molar concentration of at least 25% of the total halide component and, in some aspects, is less than about 80%. In several aspects, the total halide component comprises at least 2% BaX2. In specific embodiments, the halide component comprises at least 4% BaX2. In some aspects, the ratio of BaX2 to other MX2 compounds in the filler may vary from about 1: 10 to about 10: 1. In one embodiment, the halide component comprises cerium halide, eg, cerium bromide, which may be present at a molar concentration of at least 4% of the halides in the filling. The sodium halide may be present at a molar percentage, which is at least twice the molar percentage of the cerium halide, for example, at least about 8 mol% of the halides in the filler. For example, the halide component of the resin comprises 20-75% Ml2, 2-1 5% Cel3, 1-1.0% Ti, and the remainder (approximately 25-77%) of Nal, either alone or with smaller amounts of other halides, it is suitable to achieve a good color display index (Ra), efficiency and a chlorine correction temperature (CCT) in an electronic ballast. Such a lamp is designed to have few premature failures in the range of 1 00 to 1 000 hours. In one embodiment, other halides other than Na, Ce, TI and M are also present in a total of not more than 10% by weight of the total halide component. These other halides can include one or more halides of a rare earth metal (RE) selected from scandium, yttrium, lanthanum, praseodymium, neodymium, promised, samarium, europium, gadolinium, erbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium. Cel3 and Til contribute to the slightly green appearance of the light, without creating an unpleasant appearance. They may exhibit some instability in the plasma, which can be overcome by the presence of Csl. The lamp can provide a corrected color temperature (CCT) between about 2500K and about 4500K, for example, between about 3500K and 4500K. The lamp may have a color display index, Ra > 70, for example, Ra > 70, and in some embodiments, Ra > 80. The color display index is a measure of the ability of the human eye to distinguish colors by light from the lamp. The lamp may have a Dccy of from about 0.01 to 0.030, for example, about 0.022. Dccy is the difference in chromaticity of the color point, on the Y axis (CCY), of that of the standard black body curve. The metal halide arc tubes are re-filled with an inert gas, to facilitate the start, such as one or more of argon, xenon and krypton. For the inert gas, xenon has advantages over argon as an igniting gas because the atoms are larger and inhibit the evaporation of the tungsten electrodes, so that the lamp lasts longer. In one embodiment, suitable for CMH lamps, the lamp is re-polished with Xe with a small addition of Kr85. The radioactive Kr85 provides ionization, which helps start. The pressure Cold filling can be approximately 60-300 Torr. In one embodiment, a cold fill pressure of at least about 1 Torr is used. In another embodiment, the cold fill pressure is up to about 240 Torr. A pressure that is too high may compromise the start. Too low pressure can lead to increased lumen depreciation during life. In an exemplary embodiment, the filling gas includes at least Ar or Xe, Hg, a trace amount of Kr85 and a halide component. In one embodiment, the lumens per watt (LPW) of the lamp at 1 00 hours of operation is at least 1 00, and in a specific mode, at least 1 1 0. The maintenance of lumen, measured as: Lumens at 8000 hr , it can be at least approximately 80%, and in a lumen mode at 1 00 h, at least 85%. The ceramic metal halide lamp may be of a three-part construction, as described in the serial application no. 1 1/040, 990. The parts are formed as green ceramic and are joined by sintering or other suitable method. With particular reference to FIGURE 2, the illustrated arc tube 1 2 may include a body portion 50 extending between end portions 52, 54. The body portion of FIGURE 2 is cylindrical or substantially cylindrical about a central axis. XX. By "substantially indian cylindrical" it is meant that the internal radius r of the body portion does not vary by more than 10% within the area between the electrode tips. Alternatively, the body may have one more shape than the loft, as illustrated in FIGURE 3. The portions final, in the illustrated embodiment, are each formed integrally and comprise a generally disc-shaped wall portion 56, 58 and an axially extending hollow leg portion 60, 62, through which the respective electrodes 18, 20 are adjusted. The leg portions may be cylindrical, as shown, or tapered so that the outer diameter decreases away from the body portion 50. The indic cylindrical wall 50 has an internal diameter D (the maximum diameter, as measured in the region). 64 between the electrode tips 38, 40 and a length L. The aspect ratio of the lamp (L / D) is defined as the length of the arc tube divided by the diameter of the internal arc tube. D may be in the range of approximately 0.8 to 3.5., L / D is from about 2.0 to about 3.0, for example, from 2.2 to 2.8, which is particularly suitable for high wattage lamps, above about 50-200 W. For lower wattage lamps, for example, those below about 1000 W, an L / D ratio of about 0.8 to 1.0 can be used. The L / D ratio may be outside these ranges, in particular if the color temperature is not considered to be of particular importance. The end portions 52, 54 are fastened in a gas-tight manner to the indi- cated cylindrical wall 50 by means of a sintered joint. The wall portions each have an opening 66, 68 defined at an inner end of an axial bore 70, 72 a through the respective leg portion 60.62. The perforations 70, 72 receive connecting wires 80, 82 through the seals 90, 92. The electrodes 1 8, 20, which are electrically connected to the connecting wires, and hence the conductors, usually comprise mainly tungsten and are approximately 8-1 00 mm in length. The connecting wires 80, 82 usually comprise niobium and molybdenum, which have coefficients of thermal expansion close to that of alumina to reduce the thermally induced stresses in the alumina leg portions and may have halide-resistant sleeves formed, for example, of Mo-AI2O3. The ceramic wall thickness (ttb) is defined as the thickness (mm) of the wall material in the central portion of the arc tube body, ttb, measured in the cylindrical portion 50 may be at least 1 mm in some particular embodiments in the case of lamps that operate at high wattage. If ttb is too low, then there tends to be inadequate heat spreading on the wall through thermal conduction. This can lead to a hot local point above the convective arc boom, which in turn causes cracking as well as a reduced limit on the wall load (WL). A thicker wall spreads heat, reducing cracking and allowing greater WL. In general, the optimum ttb increases with the size of the arc tube; older wattajes benefit from larger arc tubes with thicker walls. In a modality, where the arc tube energy is in the range of 250-400W, 1 .1 mm < ttb < 1.5 mm. For minor wattages, for example, less than about 200 W, the wall thickness ttb may be somewhat smaller. If WL is too low, then the arc tube material may tend to become too hot, leading to smoothing in the case of quartz, or evaporation in the case of ceramics. The arc gap d is the distance between the tips 38, 40 of the electrodes 1 8, 20. The distance tts is defined as the distance from the electrode putna to the respective wall 56, 58 defining the inner end of the tube body of Arc. Optimization of tts leads to an end structure sufficiently hot to provide the desired halide pressure, but not too hot to initiate corrosion of the ceramic material. In one embodiment, tts is approximately 2.9-3.3 mm. In another modality, tts ~ 3.1 mm. The arc tube legs 60, 62 provide a thermal transition between the higher ceramic body end temperatures desirable for arc tube performance and the lower desirable temperatures for maintaining the seals 90, 92 at the ends of the legs. The minimum internal diameter of the legs is dependent on the diameter of the electrode-conductor, which in turn is dependent on the arc current to be supported during the start and continuous operation. The end wall portions are provided with a thickness sufficiently large to scatter the heat but small enough to prevent or minimize the blocking of light. Discrete interior corners 1 00 provide a preferred location for halide condensation. The illustrated ring tube 1 2 is formed from three components, which are sealed together during sintering. It will be appreciated that the arc tube can be constructed from a smaller or greater variety of components, such as one to five components. In a five-component structure, the plug members are replaced by separate end wall and leg members, which are joined to each other during assembly. The body member and plug members can be constructed by pressing a mixture of a ceramic powder and a binder into a solid cylinder. Typically, the mixture comprises 95-98% by weight of ceramic powder and 2-5% by weight of organic binder. The ceramic powder may comprise alumina (Al203) having a purity of at least 99.98% and a surface area of about 2-10 m2 / g. The alumina powder can be doped with magnesia to inhibit the growth of grains, for example in an amount equal to 0.03% -0.2%, in one embodiment, 0.05%, by weight of the alumina. Other ceramic materials, which may be used include non-reactive refractory oxides and oxynitrides, such as yttrium oxide, lutetium oxide and hafnium oxide and their solid solutions and compounds with alumina, such as, lyrium-aluminum-garnet and oxynitride. aluminum. Binders that can be used singly or in combination include organic polymers, such as polyols, polyvinyl alcohol, vinyl acetates, acrylates, cellulosics and polyesters. An exemplary composition that can be used to press with a solid cylinder, comprises 97% by weight of alumina powder having a surface area of 7 m2 / g, available from Baikowski International, Charlotte, N. C. as product number CR7. The alumina powder was doped with magnesia in the amount of 0.1% by weight of the alumina. An exemplary binder includes 2.5 wt.% Polyvinyl alcohol and 1/2 wt.% Carbowax 600, available from Interstate Chemical. Subsequent to die pressing, the binder is removed from the green part, usually by thermal pyrolysis, to form an unburned porcelain part burned. Thermal pyrolysis can be conducted, for example, by heating the green part in room temperature air to a maximum temperature of about 900-1 1 00 ° C over 4-8 hours, then holding the maximum temperature for 1 -5 hours, and then cool the part. After thermal pyrolysis, the porosity of the unburned porcelain part burned is normally about 40-50%. The part of unburned porcelain burned is then worked.

The carved parts are normally assembled before sintering to allow the sintering step to join the parts together. The parts may be of different densities, so that they have different shrinkage properties and thus form a seal on the sintering. The sintering step can be performed by heating the unglazed porcelain parts burned in hydrogen having a dew point of about 10-1 5 ° C. Normally, the temperature is increased from room temperature to about 850-1 880 ° C in stages, then sustained at 1 850-1 880 ° C for about 3-5 hours. Finally, the temperature is decreased to room temperature in a cooling period. The inclusion of magnesia in the ceramic powder normally inhibits the grain size from growing more than 75 microns. The resulting ceramic material comprises a densely sintered polycrystalline alumina. The seals 90, 92 normally comprise a silica-alumina-dysprosia glass and can be formed by placing a glass frit in the form of a ring around one of the connecting wires 80, 82, aligning the arc tube 12 vertically, and melting the frit. The molten glass then flows downward toward the leg 60,62, forming a seal 90, 92 between the conductor and the leg. The arc tube is then turned upside down to seal the other leg after being filled with the filler material. According to another exemplary method of construction, the component parts of the discharge chamber are formed by injection molding a mixture comprising about 45-60% by volume of ceramic material and about 55-40% by volume of binder. The ceramic material may comprise an alumina powder having a surface area of about 1.5 to about 10 m2 / g, typically between 3-5 m2 / g. According to one embodiment, the alumina powder has a purity of at least 99.98%. The alumina powder can be doped with magnesia to inhibit the growth of grains, for example, in an amount equal to 0.03% -0.2%, for example, 0.05%, by weight of the alumina. The binder may comprise a mixture of wax or a polymer mixture. In the injection molding process, the mixture of material from Ceramic and binder is heated to form a high viscosity mixture. The mixture is then injected ia properly configured mold and subsequently cooled to form a molded part. Subsequent to injection molding, the binder is removed from the molded part, usually by heat treatment, to form an unbonded part. The heat treatment can be conducted by heating the molded part in air or a controlled environment, for example, vacuum, nitrogen, rare gas, at a maximum emperature, and then holding the maximum temperature. For example, the temperature can be increased slowly by approximately 2-3 ° C per hour from room temperature to a temperature of 160 ° C. Then, the temperature is increased or approximately 1 00 ° C per hour up to a maximum temperature of 900-1 1 00 ° C. Finally, the temperature is maintained at 900-1,100 ° C for about 1 -5 hours. The part is subsequently cooled. After the heat treatment step, the porosity is approximately 40-50%. The burned non-glazed porcelain parts are normally assembled before sintering to allow the sintering step to join the parts together, in a manner similar to that discussed above. Without intending to limit the scope of the present invention, the following example demonstrates the formation of lamps using ceramic vessels with improved performance.

EXAMPLE The arc tubes are formed according to the shape shown in FIGURE 2 from three component parts. The internal diameter D is -5.8 mm and the internal length L is -7.6 mm. A filling comprises ~5 mg of halide in the proportions by weight given in Table 1 is used to form the lamps. The metal halide arc tubes are re-filled with a rare gas, comprising Ar or Xe and a small addition of Kr85. The cold filling pressure is 120-300 Torr. The arc tubes are mounted on lamps having an outer vacuum jacket and which are run to 70W electronic ballasts. The geometry of the arc tube leg, connection wire design, seal parameters and outer jacket are the same for all tested lamps. The lamps formed as described above are run in a vertical orientation (ie, as illustrated in FIGURE 3) with the lamp cap positioned higher at 70W. Table 1 shows the results obtained after 1 00 hours. CCX and CCY are the chromaticity X and Y, respectively, in a standard IEC diagram. The results are the average of 10-1 lamps.

Table 1 Table 2 These results indicate comparable properties for lamps containing barium iodide to calcium iodide lamps, even at a lower mole% in the dose. The invention has been described with reference to preferred embodiments. Obviously, modifications and alterations will occur to others about reading and understanding the preceding detailed description. It is intended that the invention be constructed as including all those modifications and alterations.

Claims (9)

1. CLAIMS 1 . A ceramic metal halide lamp (10) comprising: a decay container vessel (1 2) formed of a ceramic material, which defines an interior space (16); an ionizable filling (17) arranged in the interior, the ionizable filling comprising an inert gas, mercury and a halide component, the halide component comprising an alkali metal halide, an alkaline earth metal halide component and optionally at least one of a rare earth halide and a Group M IAA halide, the alkaline earth metal halide component comprising at least one of a barium halide and a strontium halide; at least one electrode (1 8, 20) positioned within the discharge vessel in order to energize the filling when an electric current is applied thereto, the lamp has a wall charge, when energized, sufficient to maintain the cycle of tungsten-halogen.
2. 2. The lamp of claim 1, wherein the alkaline earth metal halide component comprises a barium halide.
3. 3. The lamp of claim 2, wherein the barium halide is at least 2 mol% of a total halide component of the filler.
4. 4. The lamp of claim 2, wherein the barium halide is at least 4 mol% of a total halide component of the filler.
5. 5. The lamp of claim 2, wherein the component of alkaline earth metal halide further comprises a strontium halide.
6. 6. The lamp of claim 2, wherein the alkaline earth metal halide component is at least 1.0 mol% of the total halide component of the filler.
7. The lamp of claim 1, wherein the sodium halide is at least 5 mol% of the halides in the filler.
8. 8. The lamp of claim 1, wherein the filler comprises a halide of group MIA, which includes a thallium halide. 9. The lamp of claim 1, in which the filler comprises a rare earth halide selected from halides of Se, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er , Tm, Yb and Lu, and combinations thereof. 0. The lamp of claim 9, wherein the rare earth halide comprises a cerium halide. eleven . The lamp of claim 1, wherein the rare earth halide comprises at least about 1% of the total halide component of the filler. 12. The lamp of claim 1, wherein the alkaline earth metal halide further comprises a magnesium halide. The lamp of claim 1, wherein the wall load is at least 30 W / cm2. 14. The lamp of claim 1, wherein the wall load is at least 50 W / cm2. The lamp of claim 1, wherein the container of discharge includes a body, which is substantially cylindrical. 1 6. A ceramic metal halide lamp, comprising: a discharge vessel formed of a ceramic material, which defines an interior space; an ionizable filler disposed in the interior space, the ionizable filler comprising an inert gas, mercury and a halide component, the halide component comprises, expressed as% of the total halide component of the filler: at least about 5 mol% of the halide sodium, optionally, from about 1% to about 10% of a metal halide of group MIA, from about 10% to about 95% of an alkaline earth metal halide, the alkaline earth metal halide comprising minus one of barium halide and strontium halide, and optionally, from about 1% to about 15% of a rare earth metal halide; and wherein the lamp has a wall load of at least 30 W / cm2. The lamp of claim 16, wherein the wall load is at least 50 W / cm2. 18. The lamp of claim 17, wherein the metal halide of group MIA is at least 1% of the total halide component of the filler.
9. 9. The lamp of claim 16, wherein the barium halide is at least 2% of the total halide component of the filler. 20. A method for operating a lamp (10) comprising: providing a discharge vessel (1 2) with an ionizable filler (1 7) comprising an inert gas, mercury and a halide component, the halide component comprising, expressed as% mol of the total halide component of the filler: at least about 5 mole of sodium halide, optionally, from about 1% to about 10% of a metal halide of group MIA, from about 10% to about 95% of an alkaline earth metal halide, comprising the halide of alkaline earth metal at least one of barium halide and strontium halide, and from about 0% to about 15% of a rare earth metal halide; and energizing the lamp to generate a discharge and provide the discharge vessel with a wall load of at least 30 W / cm2.