Classical and Relaxor Ferroelectric Behavior of Titanate of Barium and Zirconium Ceramics
Résumé
BaZrxTi1-xO3 (BZT) (x = 0 to 1) and BaZr0.05Ti0.95-y(Zn1/3Nb2/3)yO3 (BZT(ZnNb)) (y = 0 to 0.1) ceramics were prepared by the conventional solid-solid reaction method. The structural, ferroelectric and dielectric properties of BZT ceramics were studied as well as the dielectric properties of the BZT(ZnNb) samples. At room temperature, the BZT ceramics present perovskite type structure and ferroelectric material's typical hysteresis cycles were obtained. However, ferroelectric and piezoelectric properties are not improved by titanium substitution of zirconium. The temperature and frequency dependence of the dielectric permittivity and loss tangent were investigated in the temperature range from 80 to 400 K and for frequencies ranging from 0.1 to 500 kHz. It was observed for BZT ceramics a classical ferroelectric behavior for 0 ≤ x ≤ 0.2, a diffuse ferroelectric to paraelectric transition for 0.25 ≤ x ≤ 0.3 and a relaxor behavior for x ≥ 0.35. The dielectric properties of the BZT(ZnNb) system were studied to obtain a new lead-free relaxor material with improved properties for electronic applications. In fact, when y increases from 0 to 0.1, a clear relaxor behavior is obtained with a reduced transition temperature and the degree of diffuseness of the phase transition increases, moreover the loss tangent decreases.