Tuning the optical and dielectric properties of calcium copper titanate CaxCu3−xTi4O12 nanopowders

Abstract

Calcium copper titanate Ca_xCu_3−xTi₄O₁₂ (CCTO) nanopowders have been synthesized using the organic acid precursor method based on commercially available materials. The results revealed that cubic CCTO phase was accomplished for the formed citrate precursors annealed at 1000 °C for 2 h. The crystallite size of the formed powders was found to increase from 44.2 to 64.8 nm upon increasing the molar ratio of Ca²⁺ ion from 1.0 to 2.0. A slight increase in the lattice parameter “a” and unit cell volume were observed, while a slight decrease in the porosity was evidenced as a result of increasing Ca²⁺ ion concentration. FE-SEM observations of these powders confirmed their homogeneous regular cubic-like structure. It can be noted that the transmittance of the sample was around 85% with Ca²⁺ ratio 1.0. Furthermore, the band gap energy increased from 3.8 to 4.2 eV, and the DC resistivity was increased from 6.4 × 10⁴ to 6.8 × 10⁴ cm Ω with increasing calcium content. We demonstrate that without any dopant, only by controlling the chemistry and engineering of the interfacial regions at the grain boundaries, the dielectric loss was suppressed remarkably while retaining the giant dielectric constant. These investigations would allow the application of these materials in transparency, microelectronics and memory devices.