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14ALT' — LD-0-9
LASER DIAGNOSTICS AND SPECTROSCOPY
Dielectric, infrared and Raman spectroscopy of BiScO3
A. Bush12, V. Kozlov2, V. Trotsenko1, E. Zhukova1, A. Serovaiskii3, V. Kutcherov3
1 - Moscow Institute of Physics and Technology (National Research University), Moscow, Russia 2 - MIREA - Russian Technological University (RTUMIREA), Moscow, Russia 3 - Gubkin Russian State University of Oil and Gas (National Research University), Moscow, Russia Main author email address: kozlov380@yandex.ru
Bismuth ferrite BiFeO3 is a unique ferromagnet that combines ferroelectric and ferrimagnetic properties. Unlike other known ferromagnetic materials, the ferroelectric Curie temperature (TC = 840 oC) and the ferrimagnetic Neel temperature (TN = 340 oC) of the compound significantly exceed the room temperature, which makes BiFeO3 promising for applications in electronic engineering [1-2]. It is considered [1] that other members of the family of the BiMO3 perovskite phases (M = Sc, Y, Cr, Mn, Fe, Co, Ni) can also exhibit ferromagnetic properties similar to those of BiFeO3. Among the series, only BiFeO3 can be formed at atmospheric pressure, while other members of the family are formed only at high pressures (6-10 GPa) [1, 3]. Due to the complexity of the synthesis of these compounds, their properties remain poorly understood. In this report, we describe the conditions for the synthesis of samples of the BiScO3 phase with a perovskite structure under thermobaric conditions, and present the results of studies of their dielectric properties, infrared and Raman spectra. Single-phase samples of the BiScO3 phase with a perovskite structure were obtained at temperatures T = 1000 - 1200 oC and pressures p = 6.0 - 7.5 GPa using a high pressure-high temperature unit URS-2 (Technological Institute of Superhard and New Carbon Materials - TISNUM, Troitsk). Detailed studies of temperature (T = 10 - 350 K) and frequency (f = 25 Hz - 1 MHz) dependences of permittivity dielectric s'(T) and dielectric loss tangent tgS(T) did not reveal any pronounced features characteristic of phase transitions. For the first time, the infrared (frequencies 30 - 15600 cm-1) and Raman (frequencies 90 - 2000 cm-1) spectra of the perovskite phase of BiScO3 were studied. Quantitative information was obtained on the parameters of infrared and Raman phonon resonances (frequency positions, dielectric contributions and damping constants). It is found that the number (48) of observed infrared modes is significantly larger than the number (27) predicted by factor group analysis performed for the noncentrosym-metric space group C2, while the number (up to 26) of observed Raman resonances corresponds to a situation with 30 active modes of the centrosymmetric group C2/c. Based on a detailed analysis of infrared and Raman spectra, it was concluded that the crystal structure of the synthesized BiScO3 phase is centrosymmetric. The additional resonances are observed in the infrared and Raman spectra and explained by the violation of the selection rules due to crystal structure distortions and/or the presence of strong local distortions of the crystal structure caused by the Bi3+ lone pair of electrons.
The research was supported by the Russian Science Foundation (grant 21-12-00358, study of dielectric properties in the low-frequency range, measurements of infrared and Raman spectra) and the Russian Foundation for Basic Research (grant 20-02-00915, part of the work on thermobaric synthesis of samples).
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