Effect of La2O3 doping on the electrical properties of 0.5Ba0.8Ca0.2TiO3-0.5BaTi0.8Sn0.2O3-0.02Pr6O11 lead-free ceramics

Lead-free piezoelectric ceramics, 0.5Ba(0.8)Ca(0.2)TiO(3)-0.5BaTi(0.8)Sn(0.2)O(3)-0.02Pr(6)O(11-x)La(2)O(3) (x = 0-0.06), were fabricated by solid-state sintering method. The effects of La2O3 addition on the phase structure, microstructure and electric properties of the ceramics were studied. The X-ray diffraction and Raman spectrum analyses revealed that La3+ ions diffused into the lattice to form a stable solid solution. Rhombohedral and tetragonal phases coexisted in the ceramics for x = 0.02-0.06. The grain growth-inhibiting effect of La doping led to an obvious decrease in grain size of ceramics from 58 mu m (x = 0) to 22 mu m (x = 0.06). The electrical properties were optimized at x = 0.04 with high piezoelectric coefficient (558 pC/N), planar electromechanical coupling factor (52.2%) and remnant polarization (7.5 mu C/cm(2)).