CN1187284C - Lead niobate zincate-lead lanthanum zirconate titanate function ceramic and preparing method thereof - Google Patents

Abstract

The invention relates to a lead niobate zincate-lead lanthanum zirconate titanate transparent functional ceramic and a preparation method thereof, which belongs to the field of transparent ceramics, and is characterized in that the transparent ceramic components are: (Pb _1-x La _x )(Zn _1/3 , Nb _2/3 ) _1-y (Zr _1-z Ti _z ) _y O ₃ where: 0<x≤0.10;0.5≤y≤0.8;0.4≤z≤0.70; prepared by oxygen and hot pressing process, During the whole sintering process, the oxygen flow rate was 3 liters/minute. The sintering temperature is 1200-1250°C, and the pressure is 480kg/cm ² . The prepared PZN-PLZT has a pure perovskite structure, the Curie temperature is 240°C, and the piezoelectric constant is between 500-700PC/N, showing the characteristics of diffusion phase transition. The transmittance is the superposition of the transmittance of PZN single crystal and PLZT ceramics.

Description

Lead niobate zincate-lanthanum lead zirconate titanate transparent functional ceramics and preparation method thereof

technical field

The invention relates to lead niobate zincate-lanthanum lead zirconate titanate transparent functional ceramics and a preparation method thereof. More precisely, it is to use an improved ceramic process to prepare a new transparent functional ceramic material with performance close to that of a single crystal. This new material combines the advantages of high performance and optical transparency of a single crystal with the large size, The invention has the characteristics of easy processing and low cost, and belongs to the field of transparent ceramic materials.

Background technique

PZN single crystal with perovskite phase structure has excellent dielectric properties, large electrostrictive effect and obvious electro-optical effect, and is the best candidate material for drivers, sensors, and optical modulators, and has great application prospects. But generally speaking, the preparation process of single crystal is complicated, the size is small, the uniform range is limited, and the cost is high, so it is difficult to realize large-scale and low-cost practical use; and the valence bond formed between each component of PZN ceramics and oxygen is weak , so the perovskite phase structure in PZN ceramics cannot exist stably, it must be modified with other perovskite structure components to form PZN ceramics with high performance perovskite structure, however, due to the traditional Advanced ceramic technology, even the modified PZN ceramics have pores and a large number of grain boundaries, so it is optically opaque, and it is impossible to realize optical applications.

Utilizing the improved ceramic process ----- hot pressing, oxygen sintering process can effectively eliminate the pores in the ceramics, the close contact between the grains makes the grain boundaries become very thin, and the ceramics of certain components can Optically transparent ceramics, such as PZLT transparent ceramics, are prepared by such a process. The transparent ceramic has a high transmittance from the visible light of 380nm to the infrared range of 11μm, showing a very obvious electro-optic effect, and can be used as an optical device such as an electro-optic shutter, light rate reduction, optical storage, and optical display. However, compared with the performance of PZN single crystal, there is still a significant gap in both optical and dielectric properties. The transmittance is lower than that of PZN single crystal, the electro-optic coefficient is an order of magnitude smaller, and the ultraviolet band is opaque, that is, the light-transmitting band is not enough. There is also a problem of large insertion loss in optical communication, which affects its practical application in optical communication.

Although PZN single crystal has particularly excellent dielectric, piezoelectric and optical properties, the growth process of single crystal is complicated, the cost is high, and the uniform area is very limited, so it is difficult to realize real application.

Can ceramic technology be used to prepare a new transparent functional material with properties close to single crystal - PZN-PLZT, to superimpose the advantages of PZN single crystal and PLZT ceramics, and to complement the original shortcomings, which leads to this purpose of the invention.

Contents of the invention

The object of the present invention is to prepare a transparent lead niobate zincate-lead zirconate titanate transparent ceramics by adopting oxygen flow and ceramic hot pressing process.

The PZN-PLZT transparent ceramic that the present invention prepares, its general formula can be expressed as:

(Pb _1-x La _x )(Zn _1/3 ，Nb _2/3 ) _1-y (Zr _1-z Ti _z ) _y O ₃

Where: 0<x≤0.10; 0.5≤y≤0.8; 0.4≤z≤0.70

The transparent _{ceramic has excellent} piezoelectric effect _{, and} its dielectric properties are _optically transparent in a wide wavelength range _. ) _0.70 O ₃ .

The PZN-PLZT ceramics provided by the present invention are prepared by a common ceramic process, uniformly mixed with _ZrO2 balls in a ball mill, dried, and ground into a uniform powder, then dry-pressed into a cylinder, and then sintered after hot pressing with oxygen . The sintering process is characterized by:

(1) Maintain an oxygen flow rate of 3 liters/minute during the sintering process;

(2) The hot pressing sintering condition is to raise the temperature to 950°C at a rate of 200°C/hour, and keep it warm for 30 minutes; then gradually increase the pressure while raising the temperature, and raise the temperature to 1200°C at the same rate, and the pressure to 480Kg/cm ² , keep warm for 6 hours; release the pressure while the temperature still rises to 1250°C at a rate of 200°C/hour, hold for 10 hours, so that the grains have enough energy for development, and then drop to 950°C at a rate of 140°C/hour, and cool with the furnace. It can also be raised to 1200°C, the pressure rises to 480Kg/cm ² , the pressure is released after 6 hours of heat preservation, and the pressure is lowered to 950°C at a rate of 140°C/hour, and then cooled with the furnace.

The phase structure of the present invention is determined by an X diffractometer (D/MAX 2550V Raguku, Japan), and a scanning electron microscope (SEM JSM-6700 field emission scanning electron microscope) is used to detect the microstructure of the sample, and the light transmission characteristics from ultraviolet to infrared are used with Perkin UV/ VIS (190nm-1100nm) and Perkin2000 (1100nm-12000nm) are measured in sections, HP4284LRC is used to study the dielectric properties of materials, and the piezoelectric constant is measured with a Berlincour instrument. The bulk density of PZN-PLZT ceramics was determined according to Archimedes' theorem.

The pure perovskite PZN-PLZT transparent ceramics with excellent properties were successfully prepared for the first time by the process of hot pressing and oxygen flow (Figure 1). There are no detectable pores in the ceramic, the grains are closely bonded, and the grain boundary is very thin (Figure 2). The density reaches 8.04 g/cm3, which is much higher than that of ordinary ceramics (7.6 g/cm3). Transparent in a wide range (Figure 3), which has not been reported so far. The study of electrical properties pointed out that, like PZN single crystal and PLZT ceramics, the dielectric constant of PZN-PLZT also exhibits the characteristics of diffusion phase transition with temperature and frequency, and the Curie temperature is 240 ° C, which is higher than that of PZN and PLZT (Fig. 4), that is, the working temperature range is wider than that of PZN and PLZT. Specimens can be up to 5 cm in diameter (Fig. 5).

The PZN-PLZT transparent ceramics provided by the invention are characterized by:

1. There are no pores in PZN-PLZT transparent ceramics that can be detected by SEM and TEM, close contact between grains, and thin grain boundaries.

2. The transmittance of PZN-PLZT transparent ceramics is the superposition of the transmittances of PZN single crystal and PLZT transparent ceramics. It has high transmittance in the range from ultraviolet 190nm to infrared 11000nm.

3. PZN-PLZT presents a pure perovskite structure, and its piezoelectric performance is higher than that of PLZT transparent ceramics. The piezoelectric constant is related to the composition, in the range of 500-700pc/N; it exhibits a dispersed phase transition behavior; the Curie temperature is 240°C , higher than those of PZN and PLZT.

4. Compared with PZN single crystal, the cost is low, the uniform area is large, and the sample diameter can reach 5 cm.

Description of drawings

Figure 1 is the X-ray diffraction spectrum of PZN-PLZT ceramics, showing the structure of pure perovskite.

Figure 2 is a SEM photo of the cross section of PZN-PLZT ceramics.

Figure 3 is the transmittance curve of PZN-PLZT ceramics in ultraviolet and infrared.

Figure 4 is the relationship between the dielectric constant of PZN-PLZT and frequency and temperature.

Figure 5 is a PZN-PLZT transparent ceramic with a diameter of 5 cm.

Detailed ways

The substantive characteristics and remarkable progress of the present invention are further illustrated below through examples, but the present invention is by no means limited to the described examples.

Example 1

Iron oxide (PbO), zinc oxide (ZnO), niobium oxide (Nb ₂ O ₅ ), zirconium oxide (ZrO ₂ ), titanium oxide (TiO ₂ ) and lanthanum oxide (La ₂ O ₃ ) as raw materials, formulated according to the chemical formula (Pb _1-0.03 La _0.03 )(Zn _1/3 Nb _2/3 ) _1-0.7 (Zr _1-0.47 Ti _0.47 ) _0.7 O ₃ For the mixed powder, put the powder into a plastic bucket filled with alcohol, mix it with zirconia balls, then dry and grind it into a uniform powder. Then press the powder into a cylinder with a diameter of 60 mm and a height of 70 mm under a pressure of 100 kg. The cylinder was sintered in a hot-press furnace, and an oxygen flow of 3 liters/min was maintained through the furnace during the sintering process. The sintering conditions are as follows: keep warm for half an hour at a rate of 200°C/hour to 950°C, and then gradually increase the pressure while increasing the temperature. When the temperature rises to 1200°C, the pressure rises to 480 kg. Under such conditions After holding for 6 hours, the pressure was removed, and the temperature continued to rise at a rate of 200°C/hour to 1250°C and held for 10 hours. Then the temperature was lowered to 950°C at a rate of 140°C/hour, and then the sample was taken out when it was naturally cooled to below 100°C. The sintered ceramic samples are cut, polished, and electrodes are made to meet the requirements of measuring electrical and optical properties.

Example 2

Prepare PZN-PLZT transparent ceramics according to the chemical formula (Pb _1-0.028 La _0.028 )(Zn _1/3 Nb _2/3 ) _0.3 (Zr _1-0.47 Ti _0.47 ) _0.7 O ₃ , and the other processes are the same as in Example 1.

Example 3

Prepare PZN-PLZT transparent ceramics according to the chemical formula (Pb _1-0.032 La _0.032 )(Zn _1/3 Nb _2/3 ) _0.3 (Zr _1-0.47 Ti _0.47 ) _0.7 O ₃ , and the other processes are the same as in Example 1.

Example 4

Prepare PZN-PLZT transparent ceramics according to the chemical formula (Pb _1-0.06 La _0.06 )(Zn _1/3 Nb _2/3 ) _0.3 (Zr _1-0.47 Ti _0.47 ) _0.7 O ₃ , and the difference from Example 1 is that the temperature is raised to 1200 ℃, the pressure is 480Kg/cm ² , after 6 hours of heat preservation, the pressure is released and the temperature is lowered without heating up.

Example 5

Prepare PZN-PLZT transparent ceramics according to the chemical formula (Pb _1-0.09 La _0.09 )(Zn _1/3 Nb _2/3 ) _0.3 (Zr _1-0.47 Ti _0.47 ) _0.7 O ₃ , and the other processes are the same as in Example 1.

Example 6

Prepare PZN-PLZT transparent ceramics according to the chemical formula (Pb _1-0.03 La _0.03 )(Zn _1/3 Nb _2/3 ) _0.3 (Zr _1-0.60 Ti _0.60 ) _0.7 O ₃ , and the other processes are the same as in Example 1.

Example 7

Prepare PZN-PLZT transparent ceramics according to the chemical formula (Pb _1-0.03 La _0.03 )(Zn _1/3 Nb _2/3 ) _0.5 (Zr _1-0.47 Ti _0.47 ) _0.5 O ₃ , and the other processes are the same as in Example 1.

Table 1 summary of embodiment performance provided by the present invention Example x Y Z components Transmittance d ₃₃ 1 0.030 0.070 0.47 (Pb _0.97 La _0.03 )(Zn _1/3 Nb _2/3 ) _0.3 (Zr _0.53 Ti _0.47 ) _0.7 O ₃ clear and transparent 620 2 0.028 0.070 0.47 (Pb _0.972 La _0.028 )(Zn _1/3 Nb _2/3 ) _0.3 (Zr _0.53 Ti _0.47 ) _0.7 O ₃ clear and transparent 570 3 0.032 0.070 0.47 (Pb _0.968 La _0.032 )(Zn _1/3 Nb _2/3 ) _0.3 (Zr _0.53 Ti _0.47 ) _0.7 O ₃ clear and transparent 470 4 0.060 0.070 0.47 (Pb _0.94 La _0.60 )(Zn _1/3 Nb _2/3 ) _0.3 (Zr _0.53 Ti _0.47 ) _0.7 O ₃ transparent 300 5 0.090 0.070 0.47 (Pb _0.91 La _0.90 )(Zn _1/3 Nb _2/3 ) _0.3 (Zr _0.53 Ti _0.47 ) _0.7 O ₃ transparent 320 6 0.030 0.070 0.60 (Pb _0.97 La _0.03 )(Zn _1/3 Nb _2/3 ) _0.3 (Zr _0.40 Ti _0.60 ) _0.7 O ₃ transparent 290 7 0.030 0.050 0.47 (Pb _0.97 La _0.03 )(Zn _1/3 Nb _2/3 ) _0.5 (Zr _0.53 Ti _0.47 ) _0.5 O ₃ transparent 150

Claims (4)

1, a kind of lead zinc niobate-lead lanthanum zirconate titanate transparent functional pottery is characterized in that the composition expression formula of described transparent functional pottery is:

(Pb _1-xLa _x)(Zn _1/3，Nb _2/3) _1-y(Zr _1-zTi _z) _yO ₃

In the formula: 0＜x≤0.10; 0.5≤y≤0.8; 0.4≤z≤0.70.

2. by the described lead zinc niobate of claim 1-lead lanthanum zirconate titanate transparent functional pottery, it is characterized in that consisting of of described transparent functional pottery:

(Pb _0.97La _0.03)(Zn _1/3，Nb _2/3) _0.3(Zr _0.53Ti _0.47) _0.70O ₃。

3, by the preparation method of the described lead zinc niobate of claim 1-lead lanthanum zirconate titanate transparent functional pottery, comprise batching, uniform mixing, drying forming and hot pressed sintering, it is characterized in that:

(1) in the whole process of hot pressed sintering, keeps 3 liters/minute oxygen flow;

(2) the hot pressed sintering condition is to be warmed up to 950 ℃ with 200 ℃/speed at one hour rating, is incubated 30 minutes; Pressurization when heating up with same speed then, when temperature is raised to 1200 ℃, pressure is raised to 480Kg/cm ², be incubated 6 hours; Release temperature then still is raised to 1250 ℃ with 200 ℃ of/hour speed, is incubated 10 hours, drops to 950 ℃ with 140 ℃ of/hour speed at last, furnace cooling.

4, by the preparation method of the described lead zinc niobate of claim 1-lead lanthanum zirconate titanate transparent functional pottery, comprise batching, uniform mixing, drying forming and hot pressed sintering, it is characterized in that:

(1) in the whole process of hot pressed sintering, keeps 3 liters/minute oxygen flow;

(2) the hot pressed sintering condition is to be warmed up to 950 ℃ with 200 ℃/speed at one hour rating, is incubated 30 minutes; Pressurization when heating up then with same speed; When temperature is raised to 1200 ℃, pressure is raised to 480Kg/cm ², be incubated 6 hours; Release and drop to 950 ℃, furnace cooling then with 140 ℃ of/hour speed.

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