Implementing a solid-state synthesis route to tune the functional properties of NaCdP3O9 metaphosphate: optical characteristics, ionic conductivity, and dielectric behavior

Abstract

An in-depth analysis of NaCdP₃O₉ was performed, exploring its structural framework, vibrational dynamics, optical absorption, and electrical behavior. The compound was synthesized using a low-cost, conventional solid-state route, resulting in a well-defined orthorhombic crystal structure assigned to the P2₁2₁2₁ space group. Optical studies identified a direct energy band gap of 3.88 eV. Dielectric measurements revealed pronounced dependencies on both frequency and temperature, with high dielectric permittivity values at low frequencies (ε′ ≈ 1.19 × 10³). Charge transport is primarily facilitated through a polaron hopping mechanism. DC conductivity followed Arrhenius behavior, indicating thermally activated motion of sodium ions with an activation energy of 0.45 eV. Additionally, AC conductivity and dielectric analyses support a conduction process involving localized charge carriers surmounting correlated energy barriers, in agreement with the correlated barrier hopping (CBH) model. This study underscores the synergy between solid-state synthetic strategies and functional property optimization, positioning metaphosphate materials as strong candidates for future sustainable electronic technologies.