MECHANICAL LOSS AND ELASTIC-MODULUS ASSOCIATED WITH PHASE-TRANSITIONSIN PLZT CERAMICS

The phase transition in lanthanum modified lead zirconate-titanate cer amic of 6160/40 is studied by mechanical loss Q(-1) and elastic modulu s measurements. The shear elastic modulus measured from 50 degrees C t o 250 degrees C shows that the Curie temperature is located at 180 deg rees C for the transition from cubic to rhombohedral phase. The Q(-1) curves at low frequencies show clearly a peak corresponding to such ph ase transition. This phase transition is confirmed by measurements of Young's modulus and Q(-1) using resonance curve technique from -100 de grees C to 300 degrees C at kilohertz. Moreover, between 50 degrees C and 90 degrees C, the resonance curve recorded at kHz frequency shows two resonance peaks. Such existence of double peaks means that a phase transition takes place between two rhombohedral phases FE2 and FE1 in the ferroelectric state. These phase transitions are also studied by DSC measurement.