Dependence of optical and dielectric properties on heat treatment of calcium-doped manganites

This work investigates Nd_0.7Ca_0.3MnO₃ (NCMO) samples, which were prepared using solid-state reaction and annealed at different temperatures (700, 800, and 900 °C). Our studies showed variations in impedance (Z), conductivity (σ), dielectric constant (ε), dielectric loss factor, and tan(δ) with frequency. From the analysis of AC conductivity, the semimetal behavior of the material was apparent when the annealing temperature increased. Impedance measurements showed characteristics of a capacitor’s dielectric material. The optical parameters of the NCMO samples were calculated from transmittance and reflectance measurements. The optical study showed that the samples have an indirect band energy gap. The resulting E_g values were 0.89, 0.94, 0.93, and 0.91 eV for the as-prepared sample and samples annealed at 700, 800, and 900 °C, respectively. With these energy gap values, the samples are suitable for photocatalysis applications in the visible light range, thus offering a low-cost alternative.

Graphical abstract

The energy gap values make these samples suitable for photocatalysis applications in the visible light range, which is considered a low-cost application.