Structural, dielectric and piezoelectric study of Ca-, Zr-modified BaTiO3 lead-free ceramics
Résumé
We prepared a lead-free ceramic (Ba0.85 Ca0.15)(Ti1−x Zrx )O3 (BCTZ) using the conventional mixed oxide
technique. The samples were prepared by an ordinary mixing and sintering technique. In this study we investigated how
small amounts of Zr 4+ can affect the crystal structure and microstructure as well as dielectric and piezoelectric properties
of BaTiO3 . X-ray diffraction analysis results indicate that no secondary phase is formed in any of the BCTZ powders for
0 ≤ x ≤ 0.1, suggesting that Zr4+ diffuses into BaTiO 3 lattices to form a solid solution. Scanning electron microscopy
micrographs revealed that the average grain size gradually increased with Zr 4+ content from 9.5 μm for x = 0.02 to 13.5 μm
for x = 0.1; Curie temperature decreased due to the small tetragonality caused by Zr 4+ addition. Owing to the polymorphic
phase transition from orthorhombic to tetragonal phase around room temperature, it was found that the composition x = 0.09
showed improved electrical properties and reached preferred values of d33 = 148 pC N−1 and Kp = 27%.