Effects of Excess Barium on the Structure and Electrical Properties of(Ba,Ca)TiO_3 Piezoelectric Ceramics with High Mechanical Quality Factors

Manganese-doped Ba_(0.925)Ca_(0.075)TiO_3 lead-free piezoelectric ceramics(abbreviated as BCT)with high mechanical quality factor were synthesized by conventional solid-state reaction method.The effects of excess Ba on the crystal structure,microstructure,and electrical properties of the ceramics were systematically investigated.X-ray diffraction and Raman spectra revealed that Ca~(2+)ions were pushed from Ba sites to Ti sites of BCT when 1.5 mol%extra Ba~(2+)ions were added after sintering.The grain size of the ceramics was decreased by adding extra Ba~(2+)ions.The mechanical quality factor and resistivity of the ceramics decreased dramatically when the excess Ba was more than 1.5 mol%.High piezoelectric coefficients(d_(33)=150-190 pC/N)and high mechanical quality factors(Q_m=1 000-1 200)were obtained in the ceramics when the excess of Ba was between 0.5 mol%and 1 mol%.These results indicated that the properties of BCT ceramics could be tailored by adjusting the content of Ba.