Curie temperature and high temperature behavior of Pb(Zr,Ti)O3/Pb(Zr,Ti)O3 sol-gel composites

The Curie temperature of Pb(Zr,Ti)O-3/Pb(Zr,Ti)O-3 (PZT/PZT) sol-gel composites was investigated empirically in order to determine the maximum operation temperature of PZT/PZT ultrasonic transducers. A PZT/PZT film was fabricated on a stainless steel substrate and the piezoelectric constant d(33) and ultrasonic response were measured after 1 h heating at a specified temperature in a furnace in order to investigate the Curie temperature indirectly. It was found that the Curie temperature of PZT/PZT was between 770 and 870 K. Second, real-time monitoring of the capacitance at various temperatures was attempted in order to measure the Curie temperature directly. A PZT/PZT film was fabricated on a stainless steel substrate and the sample was placed in a furnace and then heated from RT to 870 K. Peaks in the capacitance appeared around 670 and 820 K; thus, it was concluded that a Curie temperature shift of PZT/PZT occurred around 820 K, which was 250K higher than that of PZT powder made from the bulk material. The high-temperature ultrasonic performance was also monitored and clear reflected echoes were clearly observed at similar to 724 K. (C) 2015 The Japan Society of Applied Physics