Microhardness, optical and dielectric behavior of yttria-stabilized zirconia–alumina composites

Zirconia/alumina composite has been prepared by chemical route followed by solid state sintering route by adding various percentage of yttria from 2 to 6 mol%. The dielectric constant and dielectric loss at room temperature have been calculated as 207, 108, 206 and 0.053, 0.031, 0.046 for 2 mol%, 4 mol% and 6 mol% yttria, respectively, at a frequency of 1 kHz. Nyquist plot analysis suggests the grain–grain boundary effects of the composite material. The complex impedance study gave the knowledge about the kind of relaxations that existing within the ceramic composite. A decrease of activation energy with an increase in frequency for higher content of yttria in the sample was noticed from the variation between AC conductivity versus inverse of the temperature, and this gave rise to positive temperature coefficient of resistance (PTCR) and negative temperature coefficient of resistance (NTCR) behavior in the composite at various frequencies. An increase in yttria content has resulted in a decrease in optical band gap of the composites.