Structural, dielectric and piezoelectric study of Ca-, Zr-modified $$\hbox {BaTiO}₃$$ BaTiO 3 lead-free ceramics

We prepared a lead-free ceramic ((hbox {Ba}_0.85hbox {Ca}_0.15)(hbox {Ti}_1-xhbox {Zr}_x)hbox {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 (hbox {Zr}⁴⁺) can affect the crystal structure and microstructure as well as dielectric and piezoelectric properties of (hbox {BaTiO}₃). X-ray diffraction analysis results indicate that no secondary phase is formed in any of the BCTZ powders for (0 le x le 0.1), suggesting that (hbox {Zr}⁴⁺) diffuses into (hbox {BaTiO}₃) lattices to form a solid solution. Scanning electron microscopy micrographs revealed that the average grain size gradually increased with (hbox {Zr}⁴⁺) content from 9.5 (upmu !hbox {m}) for (x = 0.02) to 13.5 (upmu !hbox {m}) for (x = 0.1); Curie temperature decreased due to the small tetragonality caused by (hbox {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 (hbox {N}^-1) and (K_{mathrm{p}} = 27\%).