Stability of perovskite-type clusters in melts for relaxor ferroelectric crystal growth

Relaxor ferroelectric single crystals with perovskite structure were novel materials which might revolutionize some applications in medical ultrasonic imaging, telecommunication and ultrasonic devices. But during crystal growth and melt solidification, pyrochlore-type phase presented now and then, which reduced the integrality and properties of ferroelectric single crystals. This work dealt with the stability of perovskite-type clusters in melts for relaxor ferroelectric crystal growth by quenching and slow cooling. Differential thermal analysis (DTA) and X-ray diffraction (XRD) were employed to ascertain the transformation temperature between perovskite-type and pyrochlore-type clusters. Investigated results indicated that clusters in Pb(Mg_1/3Nb_2/3)O₃–32PbTiO₃ (PMN–32PT) melt which was under suitable temperature and prepared by proper pre-synthetic method were all and singular of perovskite-type structure, which established the fundament of PMN–32PT relaxor ferroelectric crystal growth from melts by Bridgman method. Whereas, clusters in Pb(Zn_1/3Nb_2/3)O₃–9PbTiO₃ (PZN–9PT) melt were of perovskite-type structure, pyrochlore-type structure, homologous PbO structure or homologous ZnO structure. During crystal growth from melts by Bridgman method, the pyrochlore phase always appeared.