Influence of defect on the electrical and optical properties of A-site non-stoichiometry Ca0.67La0.22□0.11Ti(1−x)CrxO3−δ perovskite

Abstract

An investigation of the dielectric dispersion, electrical properties, scaling behavior and optical defects of Ca_0.67La_0.22□_0.11Ti_(1−x)Cr_xO_3−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 Ca_0.67La_0.22TiO₃ (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 Ca_0.67La_0.22Ti_0.9Cr_0.1O₃ (CLT_0.9Cr_0.1) 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 CLT_0.9Cr_0.1 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.