Dielectric and piezoelectric properties of PZT ceramics doped with strontium and lanthanum

PZT based piezoelectric ceramics obtained by doping with various levels of Sr2+ and La3+, designated as PSLZT, were prepared by conventional processing techniques. The effects of Sr2+ and La3+ additions, and that of the Zr/Ti ratio on microstructure, on phase constitution, and on the dielectric and piezoelectric properties were investigated. XRD data revealed that all PSLZT compositions had perovskite structure in which increasing Sr and/or decreasing Zr/Ti ratio increased the tetragonality. In PSLZT ceramics the morphotropic phase boundary (MPB) appeared as regions extending from Zr/Ti ratio of 52/48 to 58/42. Among all compositions studied, the PSLZT ceramic having 5 at% Sr2+ and 1 at% La3+ with a Zr/Ti ratio of 54/46 exhibited a peak piezoelectric strain coefficient of d33 = 640 pC/N with attending dielectric and electromechanical parameters K33T=1800, kp = 0.56, Qm = 70, and tan δ = 1.55%.