Conferences

Relative Density and Electrical Properties of A1N with Additions Depending on Starting Composition and Hot Pressing Temperature

   

I. M. Frantsevich Institute for Problems of Materials Science of the NAS of Ukraine, Krzhizhanovsky str., 3, Kyiv, 03142, Ukraine
Powder Metallurgy - Kiev: Frantsevich Institute for Problems of Materials Science NASU, 2014, #05/06
http://www.materials.kiev.ua/article/1227

Abstract

The paper examines the effect of additions (TiO2, TiH2, TiN, and TiC up to 4 vol.%) and isothermal holding temperature on the dielectric properties of hot-pressed AlN ceramics in a wide frequency range. It is established that the service characteristics of AlN–TiO2 ceramics show a parabolic dependence on titanium oxide additions: optimal porosity (0.1%), dielectric permeability (9.7), and dielectric loss tangent (1.3 ∙ 10-3) are reached with 0.5 to 2 vol.%. TiO2. Additions of TiН2 promote the formation of metallic films mainly oriented along the pressing direction. Deviation of sintering temperature from the optimal value increases conduction-induced losses since structures with more defects and conducting phases form. It is shown that broadband ((103–107 Hz) dielectric spectroscopy can be used to monitor the composite"s microstructure: the frequency of migration polarization dispersion provided information on the effective thickness of the conducting channel and the slope σ(ω) allowed the lattice and jump responses to be differentiated.


ALUMINUM NITRIDE, DEFECTS, DIELECTRIC RESPONSE, HOT PRESSING, NONDESTRUCTIVE EXAMINATION, POLARIZATION