15 октомври 2020
Harizanova, R., Avramova, I., Cherkezova-Zheleva, Z., Paneva, D., Kukeva, R., Stoyanova, R., Gugov, I., Mihailova, I., Tzankov, D., Georgieva, M., Avdeev, G., Bocker, C., Russel, C..
(
Даниела Панева;
Зара Черкезова-Желева;
)
Abstract
Glass-ceramics with cubic BaTiO3 as a major and hexagonal BaTi1-xFexO3-? as a second phase were prepared by crystallization at 560°C in a glass with the composition 20.1Na2O/23TiO2/23.1BaO/3Al2O3/7.6B2O3/17.4SiO2/5.8Fe2O3. X-ray photoelectron spectroscopy revealed presence of Ti4+ and Fe3+ ions in tetrahedral and octahedral coordination. Ba2+ occurs in different environments depending on the thermal history of the samples. The numbers of bridging and non-bridging oxygens vary with the crystallization time. Electron paramagnetic resonance spectroscopy showed four types of Fe3+ ions that are non-uniformly distributed in the samples: Fe3+ ions in magnetic domains, isolated Fe3+ in a rhombic crystal field, magnetically coupled Fe3+ ions in BaTiO3 and Fe3+ ions located in a crystalline phase. The ratio between the described types of Fe3+ ions depends on the annealing time. M?ssbauer spectroscopy detected Fe3+ tetrahedral and octahedral coordinated in the glass. Fe3+ was incorporated in distorted octahedral and pentahedral coordination in the Ti4+ sites of hexagonal BaTiO3 crystals, the electroneutrality being preserved by the occurrence of oxygen vacancies. Vibrating sample magnetometer measurements were used to determine ferromagnetic properties in samples crystallized for times ? 3?h. Maximum magnetization of 0.8 emu/g and a coercive force of 25?Oe were determined for the sample crystallized for 3?h at 560°C.
Journal of Non-Crystalline Solids, 546, ELSEVIER, 2020, ISSN:0022-3093 eISSN: 1873-4812, DOI:10.1016/j.jnoncrysol.2020.120273, art.120273. SJR (Scopus):0.712 Q1, не оглавява ранглистата (Scopus)
https://www.sciencedirect.com/science/article/abs/pii/S0022309320303860
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