PHASE-TRANSITIONS IN NB-DOPED PB(ZR0.95TI0.05)O-3 CERAMICS INVESTIGATED BY DIELECTRIC, PYROELECTRIC AND RAMAN-SCATTERING MEASUREMENTS

Dielectric and other complementary measurements were carried out in or der to confirm the A(O)-F-R(LT)-F-R(HT)-P-C phase sequence and to dete rmine the temperatures of each phase transition occurring in undoped P ZT ceramics with Zr/Ti ratio 95/5 and Nb-doped ceramics with 0.25 divi ded by 1 weight % of Nb2O5. These measurements revealed the diffused c haracter of particular phase transitions and especially of the A(O)-F- R(LT) one. The A(O)-F-R(LT) and F-R(LT)-F-R(BT) phase transitions occu r only in the part of sample volume in the vicinities of the determine d temperatures of these transitions and the first one is extremaly bro adened and extended towards the low temperatures in the remaining volu me of the crystal. Temperature evolution of Raman spectra and the cent ral peak revealed changes of the structure, frequencies and intensity of the scattered light in each phase transition.