Piezoelectric properties of modified PZT ceramics

The systematic study of the influence of La, Li, Na, K and Bi dopants on structural (lattice parameters and particle size) and electrical (dielectric constant, dielectric loss and piezoelectric coefficients) properties of PZT have been reported. The observed single phase rhombohedral structure implies that dopants and PZT form solid solutions of PZT over whole range of additives. As the change in d-values was found insignificant, it is concluded that the final structure is invariant. The apparent density of the compounds has been observed between 7.2 to 7.6 gm/cm(3), and specific density are about between 93 to 98% of the theoretical densities at sintering temperature ranging from 1100-1200 degrees C. In all the compounds the regions around the dielectric peak are broadened. The broadening of the dielectric peak and decrease in the maximum value of dielectric constant values are consistent with the decrease in the grain size as the concentration of dopants increases. The ferroelectric Curie temperature was found to decrease with increase of La3+ concentration and other dopants have no effect on shift of Curie temperature. We did not find any systematic increase or decrease of dissipation factor (tan delta). Diffusivity gamma of the compounds was found to vary between 1 and 2, which indicates the degree of structural disorder in different compounds based on particular doping. The activation energy of the samples calculated from the paraelectric region was found to be between 1.12 to 4.6 eV. It has been found that there is a marked influence on the piezoelectric parameter d(33), K-p , and N-p with the doping of ions. The highest value of the piezoelectric coefficients has been observed with (La-0.5 D-0.5 ) = 2(+) .