Effect of defect on the nonlinear and dielectric property of Ca(1–x)SrxCu3Ti4O12 ceramics synthesized by sol–gel process

• Ca(1−x)SrxCu3Ti4O12 ceramics are synthesized by sol–gel process.
• Positron annihilation lifetime spectra is used to investigate the defects of samples.
• Nonlinear and dielectric properties are controlled by density and defects of samples.

Ca(1−x)SrxCu3Ti4O12 (x = 0, 0.05, 0.1, 0.15, 0.2, 0.3 and 0.4) ceramics are synthesized by sol–gel process. The XRD patterns show that weak peaks of Sr4Ti3O10, TiO2 and Ca1.7Sr0.3CuO3 begin to appear at x ⩾ 0.2. Sr-doping is conductive to increase the density and reduce the defect concentration Ca(1−x)SrxCu3Ti4O12 ceramics as x ⩽ 0.15. With increasing x (0.2 ⩽ x ⩽ 0.4), Sr-doping reduces the density and enhances the concentration of defects for the ceramics. The nonlinear coefficient value increases and reaches a maximum 13.5 at x = 0.15, and then decreases gradually with increasing x. The dielectric properties demonstrate that, as x ⩽ 0.15, Sr-doping not only increases the dielectric permittivity value and decreases the dielectric loss but also reduces the dependence on frequency at low frequencies. With increasing x (0.2 ⩽ x ⩽ 0.4), Sr-doping begins to lead to an inverse result in dielectric behaviors. The nonlinear and dielectric properties of Ca(1−x)SrxCu3Ti4O12 ceramics are directly controlled by the density and defects.