OPTIMUM LA CONCENTRATION FOR LEAD LANTHANUM ZIRCONATE-TITANATE (PLZT)PIEZOELECTRICS

PLZT ceramics were prepared with formulations Pb1-3x/2 La-x(Zr0.55Ti0. 45)O-3 (series A) and Pb1-xLax(Zr0.55Ti0.45)(1-x/4)O-3 (series B) for values of x less than or equal to 5. Minimum microstructural porosity, with maximum mass density, was observed at 3 at.% La in both composit ional series. The lower La concentration limit of the tetragonal phase was identified with the peak in axial ratio, which occurs at 3 at.% L a. With increasing additions of La, the static dielectric constant is increased, while the dielectric loss is decreased, and both parameters exhibit plateau values between 3-4 at.% La. The resonant frequencies and the frequency constant pass through shallow minima at 2 at.% La, w hile the piezoelectric strain constants have maximum numerical values at 3 at.% La. The optimum La concentration for PLZT ceramics with 55Pb ZrO(3):45PbTiZrO(3) is concluded to be 3 at.% La, using the formulatio n of series A, which gives consistently greater enhancement compared t o series B.