Structural, dielectric and piezoelectric study of Ca-, Zr-modified BaTiO3 lead-free ceramics

摘要

We prepared a lead-free ceramic (Ba0.85Ca0.15)(Til-xZrx)O-3 (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 Zr4+ 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 BaTiO3 lattices to form a solid solution. Scanning electron microscopy micrographs revealed that the average grain size gradually increased with Zr4+ content from 9.5 mu m for x = 0.02 to 13.5 mu m for x = 0.1; Curie temperature decreased due to the small tetragonality caused by Zr4+ 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 d(33) = 148 pC N-1 and K-p = 27%.