The first silver bismuth borate, AgBi 2B 5O 11 (silver dibismuth pentaborate), has been prepared via glass crystallization in the Ag 2O–Bi 2O 3–B 2O 3 system and characterized by single-crystal X-ray diffraction. Its structure is derived from that of centrosymmetric Bi 3B 5O 12 by ordered substitution of one Bi 3+ ion for Ag +, which results in the disappearance of the mirror plane and inversion centre. Second harmonic generation (SHG) measurements confirm the acentric crystal structure. It is formed by [Bi 2B 5O 11] ∞ layers stretched along c and comprised of vertex-sharing B 5O 10 and BiO 3 groups which incorporate the Ag + cations. The new compound was characterized by thermal analysis, high-temperature powder X-ray diffraction, and vibrational and UV–Vis–NIR (near infrared) spectroscopy. Its thermal expansion is strongly anisotropic due to the presence of rigid B 5O 10 groups aligned in a parallel manner. The minimal value is observed along their axis [parallel to c, α c = 3.1 (1) × 10 −6 K −1], while maximal values are observed in the ab plane [α a = 20.4 (2) and α b = 7.8 (2) × 10 −6 K −1]. Upon heating, AgBi 2B 5O 11 starts to decay above 684 K due to partial reduction of silver; incongruent melting is observed at 861 K. According to density functional theory (DFT) band-structure calculations, the new compound is a semiconductor with an indirect energy gap of 3.57 eV, which agrees with the experimental data (absorption onset at 380 nm).
|Журнал||Acta Crystallographica Section C: Structural Chemistry|
|Состояние||Опубликовано - июл 2019|
Предметные области Scopus
- Физика конденсатов
- Физическая и теоретическая химия
- Неорганическая химия
- Химия материалов