Relaxor ferroelectrics: Cluster glass ground state via random fields and random bonds

Quenched random fields (RFs) are well-known to be a basic driving force of the relaxor behavior in disordered ferroelectrics containing either random charges as in PbMg1/3Nb2/3O3 or random cation vacancies as in SrxBa1-xNb2O6. They give rise to the formation of polar nanoregions in the paraelectric regime, which freeze into a nanodomain state at low temperatures thus precluding the ferroelectric phase transition. On the other hand, isovalent relaxors like bond-disordered BaTi1-xZrxO3 prevalently experience random bonds (RBs), which are responsible for glassy features such as polydispersivity and non-ergodic aging and rejuvenation processes. Inspection shows, however, that all of the above characteristics apply generally to relaxor systems albeit with different weight. Subsequent formation of ferroic nanoregions via RFs followed by mesoscopic cluster glassy freezing via RBs upon cooling are universal signatures. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim