Existence of monoclinic and tetragonal zirconia in MgO substituted alumina zirconia composites and studies of dielectric behavior

Abstract

Magnesia stabilized zirconia-alumina composite were processed by auto-combustion method followed by solid-state sintering. Tetragonal zirconia with orthorhombic alumina phase has been ensured from XRD patterns and from Raman spectra. The optical band gap energy for 2%, 4% and 6% magnesium oxide substituted zirconia-alumina composites are 4.91, 5.03 and 3.48 eV, respectively. The dielectric behavior between the frequency range of 1 kHz–1 MHz shows frequency independent nature of dielectric constant with low loss tangent at various temperatures. The non-Debye type and grain-grain boundary effects were confirmed from Nyquist plot. Both PTCR and NTCR behavior were observed from AC conductivity study.