IBLC effect leading to colossal dielectric constant in layered structured Eu2CuO4 ceramic

Abstract Dielectric ( e r ′) studies of phase pure T′-type Eu 2 CuO 4 ceramics of two markedly different grain sizes ( D ), prepared by (i) conventional powder mixing and (ii) citrate complexation-Pechini process, have been carried out in the frequency range 0.1 Hz to 1 MHz, and at temperatures −100 °C to 150 °C. e r ′ is found to be highly grain size dependent. For the sample with coarse bar-like grains ( D 2 ~17×6 μm 2 ) e r ′ is >10 3 , and for the finer grain size sample with bimodal distribution ( D 1 ~1 μm, D 2 ~3 μm) e r ′ is ~10 5 ; for both the samples, high e r ′ value is nearly frequency independent over 500 Hz≤ f T ≥30 °C. The impedance spectroscopy (IS) study has clearly shown that both, the coarse- and the fine-grained samples consist of semiconducting grains and insulating grain boundaries that primarily lead to an internal barrier layer capacitance (IBLC) effect. And thus, manifest colossal dielectric constant ( e r ′>10 3 ) in Eu 2 CuO 4 ceramics. The smaller grain size (Pechini) sample, with over an order higher number of grains and grain boundary network, showing over an order higher e r ′ (~10 5 ) compared to the coarse grained one, further endorses the IBLC effect.