Silicon nitride ceramics thermal expansion

I. Peterson and T. Tien, Effect of the Grain Boundary Thermal Expansion Coefficient on the Fracture Toughness in Silicon Nitride , J. Am. Ceram. Soc., 78, [9], 1995, 2345-52. 

Aluminum nitride (AlN) has interesting properties, such as a high thermal conductivity (70-210 W m for the polycrystalline material, and up to 285 W m for single crystals), a high volume resistance, and moderate dielectric properties. The thermal expansion coefficient of AlN is close to that of silicon, and it is one of the most mechanically strong and thermally stable ceramics. These excellent attributes make AlN a useful material for many applications [160, 161]. 

Aluminum nitride, AIN, is a refractory ceramic with low dielectric constant, high intrinsic thermal conductivity, and a low coefficient of thermal expansion very close to that of silicon. In fact, aluminum nitride is one of only few materials which is both a good electrical insulator and a good thermal conductor. Consequently, there is widespread interest in its use as a replacement for alumina and beiyllia in electronic packa g applications. Such a high degree of interest in AIN stems from its high thermal conductivity, which has been measured at 319 W/m K on a single crystal (7). The theoretical value is 320 W/m-K. 

Among non-oxide ceramics, aluminum nitride developed recently. Its mechanical properties (hardness, breaking strength) are modest, bnt its thermal conductivity is very high. This conductivity associated with high electrical resistance, good dielectric property and a coefficient of expansion close to that of silicon, which varies linearly with the temperature, make it an excellent material for substrates for power micro-electronics (Figure 7.12). 

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