Structural, dielectric, optical and photocatalytic properties of (Na_0.5Bi_0.5)ZrO₃ lead-free perovskite: insights from experimental and ab initio theoretical studies

Abstract In this work, we present structural, dielectric, optical and photocatalytic properties of the room temperature phase of the lead-free perovskite (Na 0.5 Bi 0.5 )ZrO 3 (NBZ) system. The structural and optical properties are analyzed by combining a first-principles density functional theoretical approach and experimental characterizations. A conventional solid-state method is used for the synthesis process. X-ray powder diffraction and Rietveld refinement of the powder patterns at room temperature showed the NBZ material to be orthorhombic perovskite belonging to the space group Pnma . The calculated lattice constants of NBZ are found to be in good agreement with the experimental results. The dielectric study revealed a diffuse phase transition (DPT) in the vicinity of 290 °C. Based on the microscopic composition fluctuation model and phenomenological theory, a reasonable and effective characterizing parameter, the diffuseness degree, of the DPT is defined. The bandgap energy is estimated using UV–Vis spectroscopy and the optical absorption spectrum. The photocatalytic performance evaluation is performed by investigating the photodegradation kinetics of different pollutants by NBZ under visible light irradiation. The highest degradation efficiency is achieved for methylene blue (MB) dye (99% within 180 min), followed by rhodamine B (RhB), Congo red (CR) and methyl orange (MO) dyes. Overall, our results suggest good efficiency for NBZ as a photocatalytic agent with implications for large-scale photocatalytic applications in environmental and energy concerns. Furthermore, our study also provides several important benchmarking results on NBZ that have not been reported so far.