Dielectric and optical properties of BaPr2Ti4O12 synthesized by solid-phase reaction

The tungsten-bronze-type BaPr2Ti4O12 ceramic, synthesized via a solid-phase reaction, exhibits a high permittivity (ε' ≈ 135.64 at 1 kHz) and ultra-low dielectric loss (tanδ ≈ 0.0014 at 1 kHz) over a broad range of temperatures and frequencies. Its dielectric properties remain stable from room temperature up to 250 °C, attributed to the restricted carriers within defect clusters, while thermally activated electrons above 250 C induce notable changes in these properties. The high grain boundary impedance of BaPr2Ti4O12 ceramics contributes to its low electrical conductivity, thereby achieving exceptionally low dielectric loss. Furthermore, a theoretical model grounded in the hysteretic elasticity theory has been proposed to effectively describe the relaxation dynamics observed in BaPr2Ti4O12. Additionally, the BaPr2Ti4O12 ceramic exhibits strong optical absorption in visible light spectrum due to its suitable bandgap of 2.4 eV and shows notable fluorescence attributed to the rare-earth Pr3+ ions.