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Structure and stability of BaTiSi 2 O 7
Author(s) -
Viani Alberto,
Palermo Andrea,
Zanardi Stefano,
Demitri Nicola,
Petrícek Václav,
Varini Federico,
Belluso Elena,
Ståhl Kenny,
Gualtieri Alessandro Francesco
Publication year - 2015
Publication title -
acta crystallographica section b
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.604
H-Index - 33
ISSN - 2052-5206
DOI - 10.1107/s2052520615002942
Subject(s) - triclinic crystal system , monoclinic crystal system , crystallography , tetragonal crystal system , crystal structure , materials science , crystal twinning , rietveld refinement , luminescence , chemistry , microstructure , optoelectronics
Due to their optical, photo‐luminescence (PL), and afterglow properties, barium titanosilicates are compounds of great interest for functional materials and light‐emitting devices. Among them, BaTiSi 2 O 7 (BTS2) is certainly one of the most intriguing; it displays peculiar properties ( e.g. PL orange emission) whose exhaustive explanation has been hampered to date by the lack of a structure model. In this work, BTS2 and the related compound BaTiSi 4 O 11 (BTS4) were synthesized through conventional solid‐state reaction methods. BTS2 invariably shows complex twinning patterns. Thus, its structure solution and Rietveld structure refinement were attempted using synchrotron powder diffraction. BTS2 was found to be an intergrowth of monoclinic and triclinic crystals. The monoclinic phase has the space group P 2 1 / n and unit cell a = 7.9836 (3), b = 10.0084 (4), c = 7.4795 (3) Å, and β = 100.321 (3)°, whereas the triclinic phase has the space group and unit cell a = 7.99385 (4), b = 10.01017 (5), c = 7.47514 (3) Å, α = 90.084 (8), β = 100.368 (8) and γ = 89.937 (9)°. These lattices can be seen as a distortion of that of tetragonal synthetic β‐BaVSi 2 O 7 with Ti in place of V. The structure models obtained from this study confirm the presence of fivefold coordinated Ti atoms in a distorted pyramidal configuration. The proposed solution supports existing theories for the explanation of the PL orange colour in BTS2.