Study of changes in the crystal structure of BaTiO3 under the effect of X-ray radiation

Abstract

X-ray diffractometers are widely used in studying the atomic structure of mono- and polycrystalline substances. The radiation source of conventional laboratory diffractometers is a soldered x-ray tube with the maximum power consumption 1 – 3 kW. The radiation spectrum of the tube is determined by the anode material (usually, these are spectrally pure metals Cr, Ni, Fe, Cu, Mo, Ag). The wavelengths of the characteristic radiation range within 0.56 – 2.29 Е. We present the results of studying the effect of X-ray radiation power on the structure of barium titanate. Comparison of the diffraction spectra of BaTiO₃ (laminar polydomain ferroelectric single crystal and nanopowder samples) showed that the spectrum structure changes significantly with an increase in the power of X-ray beam (CuKα radiation) from 100 (5 mA, 20 kV) to 800 W (20 mA, 40 kV). For example, a rearrangement of the domain structure and, hence, a change in the dielectric characteristics of the material were observed for BaTiO₃ single crystal. The rearrangement was accompanied by the formation of continuous transition zones (between domains) containing a cubic phase. As for the BaTiO₃ nanopowder, a change in the structure was observed in the direction of the axis of spontaneous polarization c and an invariance of the structure in the plane a – c. The results obtained can be used to control the physical properties of ferroelectric and ferroelastic materials, in particular, the memristor characteristics of epitaxial films based on YBa₂Cu₃O_7–δ due to changes in their twin structure under X-ray irradiation.