DOI: https://doi.org/10.55373/mjchem.v25i3.184

Keywords: Bulk permittivities; CaTa4O11; equivalent circuit; non-Debye response; solid state

Abstract

CaTa4O11 and solid solutions with general formula CaTa4-xNbxO11 (0 ≤ x ≤ 2) have been prepared and characterised using conventional solid state technique. The structures are determined on the basis of X-ray diffraction investigation which are fully indexed on hexagonal, space group P6322. They consist of single layers of TaO7 pentagonal bipyramids alternating with layers of CaO8 octahedra. The electrical properties of these phases have been determined and all have shown excellent insulating behavior. The permittivities, ε’ are in the range between 33 – 44 at room temperature which increased with the increasing Nb-dopant concentration, whilst their conductivities, σ’ are too small to be measured at low temperature. The equivalent circuits have been carried out for all temperatures to identify the parameters that contribute to the data. At the lowest temperature, the equivalent circuit consists of a simple capacitor, whilst at the highest, the experimental data are modelled using a non-Debye response in series with a parallel combination of resistance and capacitance of the grain boundary.