Conductivity alumina-based ceramics

Although beryllium oxide [1304-56-9] is in many ways superior to most commonly used alumina-based ceramics, the principal drawback of beryUia-based ceramics is their toxicity thus they should be handled with care. The thermal conductivity of beryUia is roughly about 10 times that of commonly used alumina-based materials (5). BeryUia [1304-56-9] has a lower dielectric constant, a lower coefficient of thermal expansion, and slightly less strength than alumina. Aluminum nitride materials have begun to appear as alternatives to beryUia. Aluminum nitride [24304-00-5] has a thermal conductivity comparable to that of beryUia, but deteriorates less with temperature the thermal conductivity of aluminum nitride can, theoreticaUy, be raised to over 300 W/(m-K) (6). The dielectric constant of aluminum nitride is comparable to that of alumina, but the coefficient of thermal expansion is lower. 

Aluminum oxide-based ceramic insulators are a common construction material for a wide variety of electrical components, including vacuum tubes. Aluminum oxide is 20 times higher in thermal conductivity than most oxides. The flexure strength of commercial high-alumina ceramics is 2-4 times greater than that of most oxide ceramics. There are drawbacks, however, to the use of alumina ceramics, including... 

Aluminum nitride- (A1N-) based ceramics have been developed as an alternative to the toxicity concerns of BeO-based materials. As shown in Fig. 5.35, the thermal conductivity of AIN is comparable to that of BeO but deteriorates less with temperature. The dielectric constant of AIN is comparable to that of alumina (a drawback) but its thermal expansion is low (4 ppm/°C). 

Ingram, M. D. (1980) Conduction and Dielectric Loss Mechanisms in beta-Alumina and Glass A Discussion Based on the Paired Interstitialcy Model, J. Am. Ceram. Soc., 63, 248-263. 

Another approach extensively apphed in recerrt years to improve the ion conductivity ((, lithiirm ion transference number (C), mechanical properties, and the electrode-electrolyte interfacial stability of a polymer electrolyte is the addition of inorganic or ceramic fillers into the polymer-salt complexes (Capiglia et al., 1999 Kim et al., 2003 Chen-Yang et al., 2008 Croce et al., 2001 Rahman et al., 2009 Shen et al., 2009 Zhang et al., 2011 Munichandratah et al., 1995 Wiec-zorek, 1992). Micro and nano-sized inorganic filler such as silicone oxide (SiO ), alumina (AI2O3), ceria (CeO ), and so on are incorporated into PEO-salt complex in an effort to improve the mechanical, thermal stabihty, and ion conductivity of PEO-based polymer electrolytes. The effect of nano-fillers on the thermal properties of the PEO-based polymer complex varies with the type of nano-particles as well as the polymer-salt complex host matrix. 

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