The Relative Density and Electrical Properties of AlN with Additives Depending on the Composition of the Mixture and the Temperature of hot Pressing
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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%), permittivity (9.7), and dielectric loss tangent (1.3 ⋅10−3) are reached with 0.5 to 2 vol.%. TiO2. Additions of TiH2 promote the formation 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 (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.
Keywordsaluminum nitride hot pressing nondestructive examination defects dielectric response polarization
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