Study of properties of lanthanum doped SrBi4Ti4O15 ferroelectric ceramics

Ceramic samples SrBi4-xLaxTi4O15 (x = 0.00, 0.10, 0.25, 0.50, 0.75, 1.00), have been prepared by solid-state reaction method. Their structure was analyzed by x-ray diffraction, and their dielectricity and ferroelectricity were measured. It is found that La-doping does not change the crystal structure of SrBi4Ti4O15. The remnant polarization (2P(r)) increases at first, then decreases with the increase of La content. The 2P(r) reaches a maximum value of 24.2 muC.cm(-2), when x is 0.25. The coercive field of SrBi3.75La0.25Ti4O15 is 60.8 kV.cm(-1). The 2P(r) increases by about 50% and the E-c decreases near 25%, compared with these of SrBi4Ti4O15. Obviously, the ferroelectricity of SrBi4Ti4O15 is improved by lanthanum doping. The temperature of phase transition (T-c) decreased with La cloping. The T-c of SrBi3.75La0.25Ti4O15 is 451 degreesC. When x = 0.75 and 1.00, the SrBi4-xLaxTi4O15 exhibit the typical characteristics of relaxor ferroelectrics.