Effect of bismuth doping on structural and electrical properties of 0.9(BaZr0.2Ti0.8O3)–0.1(Ba0.7Ca0.3TiO3) ceramic
Résumé
The (Ba0.97Ca0.03)1−3y/2BiyZr0.18Ti0.82O3 ceramic system was prepared by the conventional solid-state sintering technique. The effect of bismuth substitution has been investigated via X-ray diffraction, Scanning electron microscopy, dielectric, electric and ferroelectric measurements. X-ray diffraction showed that these compounds crystallized, at room temperature, in tetragonal P4mm space group symmetry for BCTZ10 and BCTZ10–0.02Bi compounds and in cubic symmetry with space group Pmm for y = 0.06; 0.08 and 0.1 compositions distorted perovskite structures. SEM images were used to observe the microstructure. The effect of the crystal structure change and microstructure features on the dielectric and ferroelectric properties of our new BCTZ10-yBi ceramic system has been discussed. The dependence of the permittivity on temperature indicated a crossover from a normal ferroelectric, for both BCTZ10 and BCTZ10–0.02 ceramics, to a relaxor state for 0.06 < y ≤ 0.1 composition compounds. The enhancement of the dielectric properties was marked by the shift of Tm to room temperature, the increase of the maxim of permittivity and the improvement of the relaxor behavior that characterizes optimal composition due to Bi3+ substitution. BCTZ10–0.06Bi ceramic exhibit the highest , with a value of 11508 at 1 kHz, at Tm of 270 k near room temperature. Both BCZT10 and BCZT-0.02Bi ceramics exhibit a hysteresis loops signature of ferroelectric behavior at room temperature. While doped BCZT-0.02Bi show just a non linear evolution of P vs. E, the increase of the spontaneous and remnant polarizations: Ps from 0.063 μC/mm2 to 0.073 μC/mm2 and Pr from 0.028 μC/mm2 to 0.040 μC/mm2 for BCZT10 and BCZT10–0.02Bi compositions, respectively, is an evidence of the enhancement of ferroelectric properties as a result of bismuth substitution on BCZT10. The electrical properties of our new BCTZ10-yBi ceramic system may be largely tunable and could be attractive for non-volatile random access memory devices.