Optimum La concentration for lead lanthanum zirconate-titanate (PLZT) piezoelectrics

PLZT ceramics were prepared with formulations Pb 1-3x/2 La x (Zr 0.55 Ti 0.45 )O 3 (series A) and Pb 1-x La x (Zr 0.55 Ti 0.45 ) 1-x/4 O 3 (series B) for values of x < 5. Minimum microstructural porosity, with maximum mass density, was observed at 3 at.% La in both compositional series. The lower La concentration limit of the tetragonal phase was identified with the peak in axial ratio, which occurs at 3 at.% La. 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, while the piezoelectric strain constants have maximum numerical values at 3 at.% La. The optimum La concentration for PLZT ceramics with 55PbZrO 3 :45PbTiZrO 3 is concluded to be 3 at.% La, using the formulation of series A, which gives consistently greater enhancement compared to series B.