Tunable phase transitions in NaNbO3 ceramics through bismuth/vacancy modification

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2021-01, Vol.9 (12), p.4289-4299
• Main Authors: Zhang, Ludan, Zhongna Yan, Chen, Tao, Luo, Hang, Zhang, Hangfeng, Taslema Khanom, Zhang, Dou, Abrahams, Isaac, Haixue Yan
• Format: Article
• Language: English
• Subjects: Bismuth; Correlation analysis; Energy storage; Evolution; High temperature; Lattice vacancies; Perovskite structure; Perovskites; Phase transitions; Raman spectroscopy; Room temperature; Sodium; Sodium compounds; Solid solutions; Thermal analysis; X ray powder diffraction
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/d0tc05969b

Sodium niobate, NaNbO3, which exhibits a perovskite structure, has recently stimulated interest in the field of energy storage capacitors, with derived solid solutions shown to have promising energy storage densities. Here A-site Bi/vacancy doping in NaNbO3 in the system Na1−3xBixV2xNbO3 (where V = vacancy and x = 0.015, 0.05, 0.10, 0.15 and 0.20) is investigated. Phase evolution was systematically examined through X-ray powder diffraction, Raman spectroscopy and thermal analysis, and is found to correlate with changes in electrical behaviour. It is shown that through tuning the Bi/vacancy content, different high temperature phases (above 550 °C) of NaNbO3, including the tetragonal P4/mbm and cubic Pm3m phases are stabilised at room temperature. The phase evolution from Pbcm (x = 0.015 and 0.05) to P4/mbm (x = 0.10 and 0.15) to Pm3m (x = 0.20) with increased Bi/vacancy content is accompanied by lattice expansion, which is explained in terms of the accommodation of increased disorder resulting from the mixed arrangement of species (xBi3+, (1 − x)Na+ and 2xVNa) on the A-site. Bismuth/vacancy modification of NaNbO3 is seen to induce relaxor-like behaviour, significantly increasing both the recoverable energy storage density and energy storage efficiency.