Aluminum nitride, structure

Table 12.3 Aluminum Nitride Structural Data at 298K...

The measures of solid state reactivity to be described include experiments on solid-gas, solid-liquid, and solid-solid chemical reaction, solid-solid structural transitions, and hot pressing-sintering in the solid state. These conditions are achieved in catalytic activity measurements of rutile and zinc oxide, in studies of the dissolution of silicon nitride and rutile, the reaction of lead oxide and zirconia to form lead zirconate, the monoclinic to tetragonal transformation in zirconia, the theta-to-alpha transformation in alumina, and the hot pressing of aluminum nitride and aluminum oxide. 

CVD plays an increasingly important part in the design and processing of advanced electronic conductors and insulators as well as related structures, such as diffusion barriers and high thermal-conductivity substrates (heat-sinks). In these areas, materials such as titanium nitride, silicon nitride, silicon oxide, diamond, and aluminum nitride are of particular importance. These compounds are all produced by CVD. 1 1 PI... 

Fibers of aluminum nitride have been produced by the melt-spinning of ethyl-alazanes derived from the reactions of triethylaluminum and ammonia.72 The spinnable products have compositions such as (I l AIN11 )c(Et2A INH2 )v(Et3 A1 ),] which probably consist of linked alazane rings and chain structures. Pyrolysis in ammonia gives aluminum nitride fibers. 

F.S. Ohuchi and M. Kohyama, Electronic Structure and Chemical Reactions at Metal/ Alumina and Metal/Aluminum Nitride Interfaces, Journal of Amercian Ceramic Society, Vol.74(No.6), 1991, p.1163. 

Numerous ceramics are deposited via chemical vapor deposition. Oxide, carbide, nitride, and boride films can all be produced from gas phase precursors. This section gives details on the production-scale reactions for materials that are widely produced. In addition, a survey of the latest research including novel precursors and chemical reactions is provided. The discussion begins with the mature technologies of silicon dioxide, aluminum oxide, and silicon nitride CVD. Then the focus turns to the deposition of thin films having characteristics that are attractive for future applications in microelectronics, micromachinery, and hard coatings for tools and parts. These materials include aluminum nitride, boron nitride, titanium nitride, titanium dioxide, silicon carbide, and mixed-metal oxides such as those of the perovskite structure and those used as high To superconductors. 

As shown Fig. 1, high-emissivity aluminum nitride materials use aluminum nitride as the matrix for transmittance and metallic tungsten particles as emissivity particles and have a structure in which the dispersion of the tungsten particles is changed in stages. 

By using a technique to form aluminum nitride and metallic tungsten into a graded structure, we were able to broaden the knowledge of high-radiant flux aluminum nitride materials. 

Aluminum nitride (AIN) differs from other A B compounds in its hexagonal wurtzite structure. The lattice parameters of this compound are a = 3.111 k, c = 4.978 A, and c/a = 1.600 [1]. Thus, the structure of aluminum nitride differs from the perfect wurtzite structure, which consists of regular tetrahedra and is characterized by the axial ratios c/a = 1.633. Moreover, aluminum nitride has distinctive physical and physicochemical properties. 

TABLE 1. Reduced Values of the Squares of the Structure Amplitudes of Aluminum Nitride... 

Fig. 1. Dependences of the reduced values of the squares of the structure amplitude determined for aluminum nitride at 19°C, on H = 2(sini>)A, for various values of I ...

Such calculations showed that the square of the structure amplitude F for aluminum nitride powder was given by the following relationships ... 

This method was used to calculate the nearest distance (uq/c) between the A1 and the N ions along the c axis from the measured values of the square of the structure amplitude. We found (Fig. 2) that Uj/c = 0.386 0.001 and that It was independent of temperature (within the limits of the experimental error). Jeffrey et al. [1] reported 0.385 for this parameter. If all the shortest atomic spacings were equal and c/a = 1.600, we should obtain Uq/c = 0.380, whereas in the case of a perfect wurtzite structure (c/a = 1.633) we should have 0.375. Hence, we concluded that the ions located within tetrahedra in tiie aluminum nitride lattice were displaced somewhat toward the base of the unit cell. The shortest distance between the Al and the... 

The values obtained for the dynamic displacements of iiie ions and of the structure factors may be used in considering the problem of atomic bondii in aluminum nitride. 

Another main group element nitride with considerable hardness is aluminum nitride, AIN. It is important as a ceramic insulator with high thermal conductivity. It has the hexagonal wurtzite type structure (h-ZnS) [111]. In contrast to the high-pressure compound c-BN, it is prepared by various methods at ambient pressure [22,112]. 

Structural and Morphological Peculiarities of Silicon, Boron, and Aluminum Nitrides - Nanosized Powders... 

Structure formation of nitrides synthesized in the SHS-Az systems is investigated. During the combustion process, the use of SHS-Az systems sodium azide-halide of azotized element in some cases allowed to get nanostruc-tured powders of titanium, borium, silicium, aluminum nitrides with particles of nanofibrous structure with fiber diameter of 50-100nm and nanocrys-talline structure with crystal average-sized of 100-200 nm. 

Aluminum nitride (AIN) is a covalent-bonded compound and has a hexagonal wurtzite-type crystal structure and a density of 3.26 gcm . Pure AlN is translucent and colorless (white in powder form), and a stable compound in inert atmospheres at temperatures up to 2000 °C. 

The samples of AIN ceramics with the best thermal conductivity are characterized by grain size of 5-10 pm. Aluminum nitride grains form continuous uniform structure without pores while the secondary phase of yttrium aluminate is... 

---