DIELECTRIC, PYROELECTRIC, PIEZOELECTRIC AND OPTICAL INVESTIGATION OF THE PHASE-TRANSITION SEQUENCE IN BAZNGEO4

The successive phase transitions of a BaZn-GeO4 crystal have been investigated by various techniques such as X-ray diffraction, DTA, dielectric, pyroelectric, piezoelectric and optical measurements from 100 K to 1300 K. The pyroelectric and optical studies have been reported for the first time in this paper. The material gives rise to a pyroelectric current from 100 K to 520 K. Five phase transitions have been detected in this temperature range by pyroelectric current measurements. The optical measurements allow the observation of four phase transitions. The birefringence decreases with rising temperature between 100 and 1300 K. A mechanism is proposed for the observed pyroelectricty.