Modulation of microstructure, optical, dielectric, and nonlinear properties of La-doped Bi2/3Cu3Ti4O12 ceramics

(Bi 1-x La x ) 2/3 Cu 3 Ti 4 O 12 ceramics were prepared via solid-state method. Their phase composition, microstructure and defect formation along with optical, dielectric, and nonlinear properties were systematically studied. Results showed that La 3+ doping reduced cation vacancies and enhanced optical band gap. The increased grain size, density, grain boundary (GB) resistance, and barrier height improved the dielectric and nonlinear properties of the doped samples. (Bi 0.95 La 0.05 ) 2/3 Cu 3 Ti 4 O 12 ceramic exhibited the highest dielectric constant of ∼25295 and low dielectric loss tangent of ∼0.062 at 10 kHz, as well as nonlinear coefficient of ∼3.21 and breakdown strength of ∼2.47 kV/cm. Huge dielectric constant in low-frequency range was associated with the presence of semiconducting grains and insulating GBs, following the internal barrier layer capacitance mechanism. Nonlinear properties originated from Schottky barriers at GBs. In addition, dielectric relaxations of all the samples were ascribed to Maxwell–Wagner relaxation related to GBs as well.