Effects of lanthanum doping on electrical and electromechanical properties of (Pb_1−xLa_x)(Zr_0.70Ti_0.30)O₃ ceramics

In this study, the effect of La doping on the structural and electrical properties of lead zirconate titanate (Pb_1−xLa_x)(Zr_0.70Ti_0.30)_1−x/4O₃ (PLZT) ceramics have been investigated where the lanthanum content were 8.0, 8.6 and 9.0 mol%. Bulk ceramic samples were synthesized via conventional solid-state reaction method. All of the PLZT ceramic samples exhibited a dispersive dielectric behavior. The maximum dielectric constants and the Curie temperature were found to decrease with increasing La content. The dielectric constants at room temperature were measured as 4069, 4112 and 3932, respectively. The Curie temperature (T_c) at 100 kHz was determined as 94 °C, 88 °C and 82 °C, respectively. The polarization versus electric field results indicated that an antiferroelectric-like character was observed at 8 mol% La-doping. However, further addition of La led to the progressive development of relaxor-like slim and slanted hysteresis loops, which still have a double hysteresis behavior. This indicated that La-doping stabilized the antiferroelectric character. The maximum and remanent polarization values and the field induced strain values of ceramics decreased with increasing La content, whereas the measured energy density and the efficiency was increased. The temperature dependence of the properties indicated a drop of ~ 33% with increasing temperature from 25 to 85 °C.