Enhanced optical, electrical and charge transport properties of NaCaP3O9 ceramics for emerging advanced technologies

Abstract

Phosphate compounds are promising for next-generation optoelectronic and electronic applications due to their versatile structures and properties. In this work, NaCaP₃O₉ (NCPO) ceramics were synthesized by a conventional solid-state method and crystallize in a pure triclinic phase (space group P), as confirmed by XRD and structural refinement. FTIR analysis verified the structural integrity through characteristic vibrational modes. Optical studies revealed a wide direct band gap of about 3.95 eV, highlighting the suitability of NCPO for ultraviolet optoelectronic applications. Dielectric and electrical investigations over wide temperature and frequency ranges demonstrated semiconducting behavior with a negative temperature coefficient of resistance. Impedance and electric modulus analyses indicated grain-dominated conduction and non-Debye relaxation behavior. The frequency-dependent conductivity follows Jonscher's law, and charge transport is governed by a thermally activated correlated barrier hopping mechanism with an activation energy of ∼0.36 eV. The estimated thermal sensitivity constant (β ≈ 3597 K) and low stability factor (SF ≈ 1.5) suggest strong thermistor performance and stable electrical properties. Overall, this study enhances the understanding of the electrical and dielectric behavior of NCPO and underscores its potential for advanced thermistor, sensor, and optoelectronic device technologies.