Role of charge compensation mechanism on phase formation, dielectric and ferroelectric properties in aliovalent Gd3+ ion modified PbMg1/3Nb2/3O3 ceramics

Abstract

Phase, microstructural, dielectric and ferroelectric properties investigation clearly reveal that the charge imbalance created due to alio-valent Gd3+-ion substitution at Pb2+ site in lead magnesium niobate should be compensated by changing B-site cation ratio instead of creating A-site or B-site vacancies. Microstructure analysis along with elemental mapping exhibit segregation of magnesium oxide (MgO) and gadolinium niobate (GdNbO4) phase, which is observed to remain invariant to the charge compensation mechanism. Fitting of frequency dependent temperature of dielectric constant maximum Tm (temperature of emax) and the Mydosh parameter K calculated from the emax (T) clearly reveals critical slowing down of polar nano-regions (PNRs) dynamics leading to super-dipolar glass state in Gd3+-ion substituted PMN, when the charge imbalance is compensated by creating B-site vacancy or changing B-site cations ratio. Precipitation of secondary (pyrochlore) phase is resulted in Gd3+-ion substituted PMN when the charge imbalance is compensated by creating A-site vacancies, which causes reduction in interaction among the PNRs and circumventing the super-dipolar glass state.