The influence of partially disordered perovskite oxide $PZN(Pb(Zn_{1/3}Nb_{2/3})O_3)$ on $F_R(LT)-F_R(HT)$ phase transition in PZT-PZN ceramics and their pyroelectric properties have been investigated with the purpose of application to sensors, and mixed sintering technique has been studied in order to obtain ceramics with a large pyroelectric coefficient and small temperature dependence.
PZT ceramics have high pyroelectric coefficient because of a phase transition from a low temperature rhombohedral phase $F_R(LT)$ to a high temperature rhombohedral ferroelectric phase $F_R(HT)$, but it was observed in the PZT ceramics that the thermal hysteresis of as much as about 8℃ in pyroelectric properties occurs in the heating and cooling processes.
The transition temperature of $F_R(LT)-F_R(HT)$ was decreased and the thermal hysteresis of the transition temperature was diminished by increasing the PZN content in PZT-PZN ternary system. For the sample PZT-PZN(80/7/13), the thermal hysteresis was almost disappeared and the pyroelectric coefficient at room temperature was 32 nc/㎠K which is larger than that of PZT ceramics. PZT-PZN(92/3/5) ceramics exhibited minimum phase transition temperature, which was 24℃, and a high pyroelectric coefficient of 300 nc/㎠K at room temperature in this study.
In the mixed sintering technique, cermic mixtures called mixed-sintering ceramics was formed by combining two perovskites which was pre-fired at a sintering temperature and reground into powder. The larger the difference in transition temperature between two perovskites, retaining a small temperature dependence of pyroelectric coefficient over a wide temperature range. The mixed sintering ceramics formed by combining equimolar amount of PZT-PZN(92/3/5) and PZT-PZN(88/7/5) exhibited a high pyroelectric coefficient of over 50 nc/㎠K, and a small temperature dependence of pyroelectric coefficient over a wide temperature range(20℃ to 100℃).
