Оксидні матеріали електронної техніки – отримання, властивості, застосування.
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Item High temperature structure and properties of lithium niobate(Національний університет "Львівська політехніка", 2012) Boysen, H.; Senyshyn, A.; Sugak, D. Yu.High temperature neutron powder diffraction experiments were carried for a thorough detailed study of the structural evolution and phase transition of lithium niobate. Already at low temperatures part of the Li ions enter the hitherto assumed empty octahedra, their amount increasing with temperature. This explains anomalies in the thermal expansion. The phase transition from the ferroelectric to the paraelectric phase proceeds in two steps, complete disordering of Li before Nb reaches its centrosymmetric site within its octahedron. Li is further disordered within the oxygen plane pointing towards relatively strong Li-O bonds. These results settle a number of controversies found in the literature and add new aspects.Item Concentration and temperature-driven phase transitions in the NdAlO3-EuAlO3 system(Видавництво Львівської політехніки, 2012) Ohon, N.; Pashuk, A.; Hoffmann, S.; Vasylechko, L.Phase and structural behaviour in the NdAlO3– EuAlO3 system has been studied in a whole concentration range. Depending on x two kinds of solid solutions Nd1-xEuxAlO3 one with rhombohedral (x £ 0.15) and one with orthorhombic (x ³ 0.25) symmetry exist at room temperature. A morphotropic phase transition occurs at x ≈ 0.20, where the co-existence of both phases was observed. First-order structural phase transition Pbnm↔R 3 c has been detected in Nd0.6Eu0.4AlO3 at 627 K both from in situ high-temperature X-ray synchrotron powder diffraction and thermal analysis data.Item Phase composition and crystal structure of the RE-substituted BiFeO3 (RE = Er, Tm, Yb)(Видавництво Львівської політехніки, 2012) Kuz, O.; Handysh, V.; Prots, Yu.; Vasylechko, L.The work deals with the study of the phase and structural behaviour of the rare-earth substituted BiFeO3. Xray powder diffraction examinations revealed that the polar R3c phase in the Bi1-xRExFeO3 systems with RE = Er, Tm and Yb do not exceed 7, 4 and 3 mol.% of rare earth, respectively. Partial substitution of Er and Tm for the Bi sites in BiFeO3 reduce the temperature of the ferroelectric phase transition R3c-Pbnm on 30-60 K.Item Concentration and temperature-driven phase transitions in the NdAlO3-EuAlO3 system(Видавництво Львівської політехніки, 2012) Ohon, N.; Pashuk, A.; Hoffmann, S.; Vasylechko, L.Phase and structural behaviour in the NdAlO3– EuAlO3 system has been studied in a whole concentration range. Depending on x two kinds of solid solutions Nd1-xEuxAlO3 one with rhombohedral (x £ 0.15) and one with orthorhombic (x ³ 0.25) symmetry exist at room temperature. A morphotropic phase transition occurs at x ≈ 0.20, where the co-existence of both phases was observed. First-order structural phase transition Pbnm↔R 3 c has been detected in Nd0.6Eu0.4AlO3 at 627 K both from in situ high-temperature X-ray synchrotron powder diffraction and thermal analysis data.Item Crystal and twin structure of LSGMn-05 anode material for SOFC(Видавництво Львівської політехніки, 2012) Tataryn, T.; Vasylechko, L.; Savytskii, D.; Berkowski, M.; Paulmann, C.; Bismayer, U.The structure of perovskite-type La0.95Sr0.05Ga0.95Mn0.05O3-x crystals has been investigated using high-resolution X-ray powder diffraction technique in the temperature range of 298–1173 К. A phase transition from orthorhombic (Pbnm) to rhombohedral (R 3 c) has been detected near 340 К. A chevron-like configuration of ferroelastic domain structure was observed in rhombohedral La0.95Sr0.05Ga0.95Mn0.05O3-x crystal using the Laue technique. The chevron-like pattern is formed by the intersection of Wtype domain walls (211), (101) and (110).