Influence of defect on the electrical and optical properties of A-site non-stoichiometry Ca0.67La0.22□0.11Ti(1-x)Cr x O3-δ perovskite

An investigation of the dielectric dispersion, electrical properties, scaling behavior and optical defects of Ca0.67La0.22□0.11Ti(1-x)Cr x O3-δ (CLT(1-x)Cr x ) with x = 0 and x = 0.1 compositions is presented. The square in the formula is attributed to a vacancy in A-site. Relaxation phenomena were studied with dielectric and modulus formalism, while, the conductivity mechanism was investigated using electrical conductivity. A high permittivity of around 104, low dielectric loss and low electrical conductivity of around 10-3 S cm-1 for Ca0.67La0.22TiO3 (CLT) was observed. These values make this composition interesting for microelectric applications. A comparison between the Z'' and M'' indicated that the short-range carrier motion dominates at low temperature and becomes less localized at high temperature. The optical defects of CLT and Ca0.67La0.22Ti0.9Cr0.1O3 (CLT0.9Cr0.1) were studied by electron paramagnetic resonance (EPR) spectroscopy. The results suggest the formation of a [TiO6]9- center, a (Ti3+-V O) center, and dipole defect for CLT compound and Cr3+-V O center defect for CLT0.9Cr0.1 compound. These defects are the source of the in-gap electron traps, which improve the optical properties of CLT(1-x)Cr x and hence make it an interesting optical material for different applications.