Abstract
Abstract In this paper, for the first time, we present the detailed temperature (−100 ≤ T ≤ 150 °C) and frequency (1 Hz ≤ f ≤ 1 MHz) dependent dielectric and ac impedance studies of the single phase, T′-type, Sm 2 CuO 4 (SCO) ceramics synthesized in nanocrystalline (particle size ( d ) ≤ 50 nm) and bulk ceramic form ( d ≤ 1 µm). SCO ceramics exhibited a colossal dielectric constant (CDC), e r ′ ≥ 10 4 , in the entire measured frequency and temperature ranges. Being non-ferroelectric and centro-symmetric, display of CDC in this SCO ceramics is extraordinary. Using impedance spectroscopy, (IS) the origin of such extraordinary values were investigated; IS study revealed electrical heterogeneity of SCO samples with semiconducting grains and resistive grain boundaries. Arrhenius plots also suggested this phenomenon, with grain boundaries showing NTCR (akin to insulators) and grains showing PTCR (akin to metals/semi-metals) behavior for the electrical conductivity. This heterogeneity in electrical microstructure could give rise to internal barrier layer capacitance (IBLC) effect, ultimately resulting in CDC (>10 4 ), in these SCO ceramics.
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