Electrical properties and diffuse phase transition of the Sr0.3−3y/2LayBa0.7Nb2O6 ceramic system

Sr0.3−3y/2LayBa0.7Nb2O6 (LSBN) is a ceramic multifunctional material with interesting electrical properties which encourage its use in optoelectronic devices. LSBN ceramic compounds with 3 % wt lanthanum have been prepared using the traditional ceramic method. Two different calcination temperatures, 900 °C and 1000 °C, were utilized looking for improvement of their electrical properties. This study is focoused in the characterization of the electrical properties and the ferroelectric-paraelectric phase transition behavior of the LSBN ceramic compunds. The dielectric properties such as dielectric constant (ε) and dielectric loss are studied as functions of temperature from room temperature to 450 °C, and frequency between 100 Hz and 1 MHz. LSBN ceramics show high dielectric constant and low dielectric loss. The samples present a diffuse phase transition (DPT) and relaxor behavior, where the dielectric constant vs. temperature curves exhibit broad peaks, and their maximum temperature Tm shifts towards higher values with increasing frequency in all cases. Experimental data for LSBN show that, for the higher calcination temperature, the maximum transition temperature Tm increases, and the maximum dielectric constant decreases. Spontaneus and remnant polarizations and coercive fields, obtained from hysteresis loops measurements, are discussed.