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 Gd 3+ -ion substitution at Pb 2+ 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 (GdNbO 4 ) phase, which is observed to remain invariant to the charge compensation mechanism. Fitting of frequency dependent temperature of dielectric constant maximum T m (temperature of  max ) and the Mydosh parameter "K" calculated from the  max (T) clearly reveals critical slowing down of polar nano-regions (PNRs) dynamics leading to super-dipolar glass state in Gd 3+ -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 Gd 3+ -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.