CN100376725C - CaB4 compound crystal and preparation method thereof - Google Patents

Abstract

The invention discloses the binary CaB4 compound crystal and preparing method. The CaB4 compound crystal is black crystal with metallic luster, the chemical composition of which is Ca: B=1: 4. The crystal structure is tetragonal structure, the space group is P4/mbm, and the crystal parameter is a=b=0.7174nm, c=0.4103nm. The method comprises the following steps: 1 mixing the Ca and B according to proportion 1:4 at Ar condition, performing, enveloping Ta; 2 treating at 1200-1600Deg.C and 1-6GPa, dissolving Ca and CaO with dilute hydrochloric acid, and getting the product. The new non-metallic material maybe is the material for making electronic component.

Description

CaB4 compound crystal and preparation method thereof

technical field

The invention relates to a novel non-metallic material, in particular to a binary _CaB4 compound crystal and a preparation method thereof.

technical background

In the binary Ca-B phase diagram (Figure 1), CaB ₆ is the only Ca-B compound. CaB ₆ is easy to prepare, such as direct reaction of metal calcium and elemental boron, can prepare high-purity CaB ₆ powder; use CaO and pure B as raw materials, 1600 ℃ for 1 hour to react to form CaB ₆ phase; use CaCO _3. CaB ₆ powder can also be obtained by heating B ₄ C and active C powder at 1400°C for 2.5 hours under vacuum. CaB ₆ has many excellent properties, such as high melting point, high strength and high chemical stability. Recently, it has been found that CaB ₆ doped with a small amount of La has a high Curie temperature (900K), and it still has a high Curie temperature (900K) at extremely high temperatures. Ferromagnetism makes it possible to become a new type of electronic component manufacturing material. Until recently, R. Schmitt et al. used Ca, B, and C as raw materials to prepare C-doped CaB _4-x C _x phases through solid-state reactions between elements. The preparation method is as follows, the ratio of raw materials is Ca: B: C = 3: 2: 1, sealed in an Ar gas environment, kept at 1000 ° C for 2 hours, and the remaining Ca in the sample and the mesophase CaC ₂ and CaB are removed with hydrochloric acid ₂ C ₂ , a black crystalline powder was obtained, that is, the CaB _4-x C _x phase. They made various attempts to prepare pure CaB ₄ without C, but were unsuccessful. Among them, including adjusting the ratio between Ca and B, the reaction temperature is in the range of 800-1200 ° C, and the temperature is kept for different times, and the CaB ₆ phase is obtained. The authors believe that the CaB _4-x C _x phase can only be formed in a C-containing environment, where the carbon content is <5%.

Contents of the invention

In order to overcome that the CaB _4-x C _x phase can only be generated in an environment containing C, the invention provides a CaB ₄ compound crystal and a preparation method thereof. The preparation method is easy to operate, and the prepared CaB ₄ compound crystal does not contain carbon.

The chemical composition of this CaB ₄ compound crystal is: Ca: B=1: 4, crystal structure is tetragonal structure, space group is P4/mbm, lattice parameter a=b=0.7174nm, c=0.4103nm, and its appearance is Metallic black crystals with metallic properties.

The preparation method of CaB ₄ compound crystal is as follows:

(1) Prepare pure Ca and B at a ratio of 1:4, fully mix and press into tablets under the environment of Ar gas, and outsource Ta tablets;

(2) After high temperature treatment at 1200-1600° C. and high pressure treatment at 1-6 GPa, dilute hydrochloric acid was used to dissolve the remaining Ca and CaO to obtain CaB ₄ compound crystals.

Description of drawings

Fig. 1 is B-Ca phase diagram;

Fig. 2 is an X-ray diffraction pattern of CaB4 crystal.

Detailed ways

Example

Prepare Ca and B at a ratio of 1:4, fully mix and press tablets in an Ar gas environment, wrap Ta tablets, and after high temperature and high pressure treatment at 1400°C and 6GPa, dissolve the remaining Ca and CaO with dilute hydrochloric acid to obtain Metallic black crystalline _CaB4 powder. The chemical composition of the CaB ₄ compound crystal is: Ca:B=1:4, the crystal structure is tetragonal, the space group is P4/mbm, the lattice parameters a=b=0.7174nm, c=0.4103nm, and has metallic properties. The X-ray diffraction pattern of CaB ₄ crystal is shown in Figure 2, and the interplanar spacing and relative intensity of each crystal plane are listed in Table 1.

Table 1 Interplanar spacing and relative strength of each crystal plane of CaB ₄ crystal

h k l d_obs( ) d_cat(A) I_obs(%) I_cat(%) h k l d_obs( ) d_cat(A) I_obs(%) I_cat(%) 10011011201120 10221223203132 01001110121212 5.05784.09243.57873.20223.18422.69642.52522.26642.15532.04911.98361.90051.78911.7789 5.073114.103713.587183.208443.190542.700782.527652.268742.157602.051851.985511.902161.790441.78108 22973326410082161194219 22773226510072160173217 11313231130213 42343345432525 02011211223130 1.73791.72701.68931.60051.56201.42681.35281.32981.32591.30391.27701.26621.25761.2291 1.740041.728591.691021.601971.563471.428441.354451.330951.327091.304951.278131.267141.258321.23039 251981442442212102115 251971442432112111115

Claims (2)

1. a binary CaB ₄ compound crystal, it is characterized in that: the appearance of the synthesized CaB ₄ compound crystal is a black crystal with metallic luster, its chemical composition is: Ca: B=1: 4, and the crystal structure is a tetragonal structure , the space group is P4/mbm, the lattice parameters a = b = 0.7174nm, c = 0.4103nm, with metallic properties. 2. a method for preparing CaB _compound crystal according to claim 1, characterized in that: (1) Prepare pure Ca and B at a ratio of 1:4, fully mix and press into tablets under the environment of Ar gas, and outsource Ta tablets; (2) After high temperature treatment at 1200-1600° C. and high pressure treatment at 1-6 GPa, dilute hydrochloric acid was used to dissolve the remaining Ca and CaO to obtain CaB ₄ compound crystals.

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