The role of calcination temperature on enhancing the dielectric and optical properties of CaCu3Ti4O11.8Cl0.2 material

Abstract

The role of calcination temperature on phase stability and dielectric properties improvement of CaCu₃Ti₄O_11.8Cl_0.2 was studied. Analysis using optical properties indicated a redshift of the absorption peaks, while the band gap energy was decreased up to 1.72 eV due to improved crystallinity and structural transformations taking place. A giant dielectric constant was reported of ε’_r = 4.1590 × 10⁴ with low dielectric losses of tanδ = 0.036 at 1 KHz for sample calcined at 900 °C/4h. The enhancement of dielectric properties was highly correlated with electrical behavior such as conductivity, activation energy (E_a), grain boundaries, and grain resistivity evolution. The findings were in accordance with the internal barrier layer capacitance (IBLC) model which considers grains and grain boundaries as critical contributors to the dielectric response. However, it is confirmed that the high value of grain boundary resistivity R_gb = 8.99 × 10⁶ Ω and low E_a = 0.28 eV are responsible for the low value of tanδ. While the low values of grain resistivity R_g = 111.67 Ω and grain growth contributed to the high ε’_r values. Moreover, the values of permittivity and losses reported in this study were compared to other halogen substitutions such as F^-, I^- and Br^- and showed better values, due to the electrical properties improvement, with the objective of making industrial capacitors and high-energy storage devices.