THE RELATIVE DENSITY AND ELECTRICAL PROPERTIES OF AIN WITH ADDITIVES DEPENDING ON THE COMPOSITION OF THE MIXTURE AND THE TEMPERATURE OF HOT PRESSING

摘要

The paper examines the effect of additions (TiO_2, TiH_2, TiN, and TiC up to 4 vol.%) and isothermalholding temperature on the dielectric properties of hot-pressed AIN ceramics in a wide frequency range. It is established that the service characteristics of AlN-TiO_2 ceramics show a parabolicdependence on titanium oxide additions: optimal porosity (0.1%), permittivity (9.7), and dielectric loss tangent (1.3 ■ 10~(3)) are reached with 0.5 to 2 vol.%. TiO_2. Additions of TiH_2 promote theformation of metallic films, mainly oriented along the pressing direction. The 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 (10~(3)~10~(7) 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.