Effects of $\gamma$ irradiation on the electric conduction of PZT ceramic system

In the work, the results of investigations of the electric conduction $\sigma$ of the PZT ceramics
with the two following compositions: Pb$_{0.94}$Sr$_{0.06}$(Zr$_{0.5}$Ti$_{0.5}$)O$_{3}$ + 0.25% wt. Cr$_{2}$O$_{3}$
(hard material) and (Pb$_{0.9}$Ba$_{0.1}$)(Zr$_{0.53}$Ti$_{0.47}$)O$_3$ + 1.67% wt. Nb$_2$O$_5$ (soft material), are
presented. The “soft” ceramics are characterized by high electric values ($\epsilon^T_{33}/\epsilon_0 > 1300$
(in room temperature), $d_{31} = 120 \cdot 10^{−12}$ C/N) and electromechanical coupling coefficient
($k_p > 0.5$). Due to good parameters it is used in electromechanical transducers of low frequency.
The “hard” PZT ceramics, which are used in resonators, filters and ultrasound transducers
are characterized by the following parameters: $\epsilon^T_{33}/\epsilon_0 > 900$ (in room temperature),
$d_{31} = 65\cdot 10^{−12}$ C/N and electromechanical coupling coefficient $k_p > 0.35$. The temperature
dependences of the electric conduction $\sigma$ for all samples before and after $\gamma$ irradiation with
dose of 20 kGy were performed. The activation energy $E_a$ was calculated on the basis of the
ln $\sigma = f(1/T)$ dependences.