Abstract
Three new isostructural mixed anionic tellurites, namely, Pb2Al3F3(Te6F2O16) (1), Pb2Ga3F3(Te6F2O16) (2) and Ba2Ga3F3(Te6F2O16) (3), have been synthesized successfully by hydrothermal reactions. Their structures feature a novel 3D framework composed of 1D GaO4F2/AlO4F2 octahedral chains joined together with isolated (Te6F2O16)10− anionic rings. The charge-balance cations of Pb2+ or Ba2+ are located at the six-member polyhedral ring tunnels of the structures. The 0D (Te6F2O16)10− coplanar anionic ring is first reported in fluorotellurites, formed by two TeO4 and four TeO3F groups via corner-sharing. Thermogravimetric analyses revealed that their thermostabilities are in the following order: Pb2Al3F3(Te6F2O16) (1), Ba2Ga3F3(Te6F2O16) (3) and Pb2Ga3F3(Te6F2O16) (2). Optical diffuse reflectance spectra showed that these solids are wide band gap semiconductors with Eg of 4.1, 4.2 and 4.4 eV for compounds 1–3 respectively. The band gaps of compounds 1 and 2 are determined by O, Te and Pb atoms while the band gap of compound 3 is determined by O and Te atoms based on the theoretical calculations.
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