Giant dielectric properties of nanocrystalline Pb_1−xSn_xF₂ solid solutions

Abstract

Nanocrystalline Pb_1−xSn_xF₂ (x = 0.2, 0.3) solid solutions have been synthesized by mechanochemical milling at room temperature with grain size as small as 26 nm. These fluoride ion conducting materials exhibit giant values of the dielectric constant of ɛ′ > 10⁵ that is independent of temperature and frequency over wide ranges. The giant values of ɛ′ are suggested to be due to internal effects in the materials. The dielectric response has been analyzed by appropriate equivalent circuit representing the grain and internal effects in the materials. Interestingly, the dielectric constant of the current samples is found to be larger for the samples with smaller grain size, a behavior that is quite opposite to what usually observed in giant dielectric oxide materials, where ɛ′ is enhanced with substantial growth of the grain size. The possible origin of the giant dielectric constant is discussed in the present study.