Phase transition, ferroelectric and piezoelectric properties of Ba1−xCaxTi1−yZryO3 lead-free ceramics

Lead-free piezoelectric ceramics Ba1−xCaxTi1−yZryO3+1mol%CuO were prepared by an ordinary sintering technique and the effects of Ca2+ and Zr4+ on phase transition and electrical properties of the ceramics were studied. The results of X-ray diffraction show that the ceramics exhibit a pure perovskite structure at 0 ≤ x ≤ 0.175 and 0 ≤ y ≤ 0.175, suggesting that Ca2+ and Zr4+ diffuse into BaTiO3 lattices to form a solid solution. The substitution of Zr4+ for the B-site Ti4+ ions of BaTiO3 decreases greatly Curie temperature TC and strengthens the relaxor character of the ceramics, while the addition of Ca2+ has a weak influence on TC and leads to an inhibition of grain growth. Owing to the more possible polarization states resulting from the coexistence of tetragonal and orthorhombic phases near room temperature, the ceramics with x = 0.075–0.125 and y = 0.1 exhibit excellent piezoelectric properties: d33 = 254–345 pC/N and kp = 38.0–45.2%, respectively.