Nanostructure and properties of Pb(Zr,Ti)O3-Pb(Ni1/3Nb2/3)O3 piezoceramics

Piezoceramics with composition 0.46 Pb(Zr0.3Ti0.7)O3 - 0.53 Pb(Ni1/3Nb2/3)O3 have been synthesized by solid-state reaction at different temperatures. The density varied between 8.05-8.1 g/cm3. The sintered samples have been chemically electroded with Ni and poled at 220 C under an electric field of 3 kV/cm. The XRD spectra confirmed the formation of tetragonal crystalline phase with a tetragonal distortion c/a = 1.0125 which was decreased from a value of about 1.042 that corresponds to pure PZT with y = 0.3. Some minor traces of non-reacted precursor oxides such as Nb2O5 have been also found. TEM results confirmed the formation of tetragonal phase and revealed crystal grains with domains of different size, slightly disoriented from each other. Dielectric measurements performed between 20 $^{\circ}$C and 300 $^{\circ}$C at different frequencies between 100 Hz and 1 MHz revealed a broad dielectric anomaly at T$_{\rm m}$ = 118 $^{\circ}$C (200 Hz) which shifts to 127 $^{\circ}$C at 1 MHz driving frequency. A dependence of T$_{\rm m}$ on sintering temperature has been observed. A thermal hysteresis is also found on heating and cooling. This shows that the samples present both relaxor and ferroelectric characteristics. High values of the dielectric constant are found both at room temperature (about 5000) and at T$_{\rm m}$ (about 18000). The dependence of dielectric and piezoelectric constants on sintering temperature has been found.