Intercalation of water molecules from the air into perovskite and layered structures formed in the system of NaNbO3-Ca2Nb2O7

J Y Zubarev; Shun-Hsyung Chang; L A Shilkina; M I Mazuritskiy; A P Budnyk; A V Nazarenko; S I Dudkina; O N Razumovskaya; L A Reznichenko; I A Parinov

doi:10.1016/j.heliyon.2019.e02786

Intercalation of water molecules from the air into perovskite and layered structures formed in the system of NaNbO₃-Ca₂Nb₂O₇

Heliyon. 2019 Nov 14;5(11):e02786. doi: 10.1016/j.heliyon.2019.e02786. eCollection 2019 Nov.

Authors

Affiliations

¹ Scientific Research Institute of Physics, Southern Federal University, Stachki av. 194, 344090, Rostov-on-Don, Russia.
² Department of Microelectronics Engineering, National Kaohsiung University of Science and Technology, Taiwan.
³ Department of Physics, Southern Federal University, Zorge st. 5b, 344090, Rostov-on-Don, Russia.
⁴ Federal Research Centre, The Southern Scientific Centre of the Russian Academy of Sciences, Chekhov Ave. 41, 344006, Rostov-on-Don, Russia.
⁵ Southern Federal University, Rostov-on-Don, Russia.

Abstract

The study results of the perovskite solid solution and layered compounds formed in the system of (1-х)NaNbO₃-xCa₂Nb₂O₇, x = 0.10, 0.25, 0.55, 1.00 are presented. The objects of the study are obtained by solid-phase synthesis, followed by sintering using conventional ceramic technology. The study of dielectric spectra has revealed their anomalous behavior in the temperature range of 360-450 K, most pronounced in the composition with x = 0.25. To explain the anomalies in these objects, a microstructural analysis of ceramics, thermogravimetry, high-temperature powder X-ray diffraction, and IR spectroscopy heve been performed. It has been established that the anomalies of the dielectric spectra in the indicated range are due to the adsorption of water from the air, its dissociation and the incorporation of the OH₂ and OH^- oxyhydryl groups into the crystal lattice of the solid solution and the compounds. In a compound located near the boundary between solid solutions and layered compounds, the process of water adsorption is accompanied by the appearance of an intermediate incommensurate phase and ends with the formation of a new compound.

Keywords: Calcium pyroniobate; Ceramics; Condensed matter physics; Layered perovskite-like compounds; Materials science; Water intercalation.