Influence of strontium and donor ion substitution on the dielectric, optical, and nonlinear characteristics of (Ca0.9Sr0.1)0.95A0.033Cu3Ti4O12 ceramics

Abstract

This study expands on a previous investigation by substituting lanthanum with various trivalent ions in the compound (Ca0.9Sr0.1)0.95A0.033Cu3Ti4O12 (A = La3+, Sm3+, Sc3+, Gd3+, Y3+ and Bi3+) through solid-state synthesis. The analysis includes microstructures, optical, dielectric, and nonlinear properties. Sr2+/A3+-doped CCTO exhibits a significant reduction in grain size. The doped samples display a band gap ranging from 3.22 eV to 3.36 eV, with high dielectric permittivity (ε'≈4.51 × 103-5.37 × 104). Additionally, Sr2+/A3+ doping enhances the thermal stability compared to pure CCTO ceramic. Specifically, Sr2+/Sc3+-doped compound shows low loss tangent (tanδ≈0.04) at 60 °C, with the dielectric loss remaining below 0.1 over a temperature range from 50 °C to 160 °C. Furthermore, there is a significant improvement in breakdown voltage (Eb = 8420 V/cm), which is 23 times higher than CCTO (362.5 V/cm), and the coefficient α increases from 3.28 to 12.76. These enhancements are attributed to inhibiting the formation of Ti3+ and reducing oxygen vacancies.