Synergistic engineering of mixing A-site cations and oxygen vacancies to boost optical, electrochemical, and dielectric properties of Ag0.5Na0.5NbO3−δ

Abstract

Ag 0.5 Na 0.5 NbO 3−δ lead-free perovskite was synthesized using a conventional solid-state method. X-ray diffraction (XRD) confirmed an orthorhombic (Pbcm) Ag 0.5 Na 0.5 NbO 3−δ perovskite phase with a small monoclinic (P2 1 /n) NaAgNb 4 O 11 phase. Transmission electron microscopy (TEM) image of Ag 0.5 Na 0.5 NbO 3−δ perovskite revealed polyhedron structures with an average particle size of approximately 73.15 nm. The surface area of 3.1786 m 2 /g and average pore size of 5.7834 nm of Ag 0.5 Na 0.5 NbO 3−δ perovskite were determined from Nitrogen (N 2 ) adsorption-desorption isotherm. X-ray photoelectron spectroscopy (XPS) revealed the coexistence of Ag 1+ /Ag 0 , Na 1+ , and Nb 5+ /Nb 4+ oxidation states alongside oxygen vacancies (δ). Optical properties of Ag 0.5 Na 0.5 NbO 3−δ perovskite exhibit semiconducting nature with direct and indirect transition band gaps of 3.63 and 2.63 eV, respectively. Electrochemical measurements of the Ag 0.5 Na 0.5 NbO 3−δ electrode exhibited pseudocapacitive behavior, and the charge storage in this electrode is the oxygen intercalation mechanism. The dielectric constant (ε r ) of Ag 0.5 Na 0.5 NbO 3−δ perovskite exhibited three dielectric anomalies within the temperature range of 291–675 K, corresponding to phase transitions. The present results suggest that Ag 0.5 Na 0.5 NbO 3−δ is a promising candidate for advanced optical, dielectric, and energy storage applications.