Effects of MnO2 and sintering temperature on microstructure, ferroelectric, and piezoelectric properties of Ba0.85Ca0.15Ti0.90Zr0.10O3 lead-free ceramics

Ba0.85Ca0.15Ti0.90Zr0.10O3 + xmol% MnO2 leadfree ceramics have been prepared by a conventional sintering method and the effects of MnO2 and sintering temperature on microstructure, ferroelectric, and piezoelectric properties of Ba0.85Ca0.15Ti0.90Zr0.10O3 lead-free ceramics have been studied. The addition of 0.25 mol% MnO2 promotes grain growth, improves the ferroelectricity of the ceramics and strengthens ferroelectric tetragonal-ferroelectric orthorhombic phase transition near 40 degrees C. Because of the coexistence of tetragonal and orthorhombic phases and the combinatory effects of soft and hard doping of Mn ions, the ceramic with x = 0.25 exhibits the optimum piezoelectric properties (d(33) = 306 pC/N and k(p) = 42.2 %, respectively). Excess MnO2 inhibits the grain growth and degrades the ferroelectric and piezoelectric properties of the ceramics. Sintering temperature has an important influence on the microstructure, tetragonal-orthorhombic phase transition near 40 degrees C, ferroelectric and piezoelectric properties of the ceramics. The increase in sintering temperature leads to large grains and more noticeable tetragonal-orthorhombic phase transition near 40 degrees C, enhances ferroelectricity and thus improves effectively the piezoelectricity of the ceramics. The Ba0.85Ca0.15Ti0.90Zr0.10O3 ceramic sintered at 1350 degrees C possesses the optimum piezoelectric constant d(33) value of 373 pC/N.