Distorted perovskites for high voltage dielectric capacitors

Abstract

There are several mechanisms which have been proposed for the existence of colossal dielectric constant in the class of perovskite calcium copper titanate (CaCu₃Ti₄O₁₂ or CCTO) materials. Researches indicate that existence of twinning parallel to (100) (001) and (010) planes causes planar defects and causes changes in local electronic structure. This change can cause insulating barriers locally which contribute to the large dielectric values irrespective of processing. The combination of insulating barriers, defects and displacements caused by twinning have been attributed to the generation of large dielectric constant in CCTO. To examine some of these arguments some researchers replaced Ca with other elements and evaluated this concept. In this study we present the synthesis and characterization of Ga₂/₃CaCu₃Ti₄O₁₂₋ₓNₓ (GCTON) material. This provides both distortion due to atomic size difference and defects due to insertion of nitrogen. The morphology of the compound was determined to show that processing has tremendous effect on the dielectric values. The resistivity of GCTON was several order higher than CCTO and dielectric constant was higher than 10,000.