Synthesis, Composition, and Structure of Sillenite-Type Solid Solutions in the Bi₂O₃−SiO₂−MnO₂ System

Abstract

Individual compounds and solid solutions are obtained under hydrothermal conditions in the Bi(2)O(3)-SiO(2)-MnO(2) system in the form of faceted crystals and epitaxial films on the Bi(24)Si(2)O(40) substrate. The crystals have the shape of a cube (for the molar ratio of the starting components Na(2)SiO(3)·9H(2)O:Mn(NO(3))(2)·6H(2)O > 1), a tetrahedron (for Na(2)SiO(3)·9H(2)O:Mn(NO(3))(2)·6H(2)O < 1), or a tetrahedron-cube combination (for Na(2)SiO(3)·9H(2)O:Mn(NO(3))(2)·6H(2)O = 1). Crystal-chemical analysis based on the data of single-crystal and powder X-ray diffraction, IR spectra, and the results of calculation of the local balance by the bond-valence method reveals formation of the Bi(24)(Si(4+),Mn(4+))(2)O(40) phases, which probably include Mn(5+) ions (epitaxial films), as well as the Bi(24)(Si(4+),Bi(3+),Mn(4+))(2)O(40) and Bi(24)(Si(4+),Mn(4+))(2)O(40) phases in the (1 - x)Bi(3+)(24)Si(4+)(2)O(40) - x(Bi(3+)(24)Mn(4+)(2)O(40)) system and the Bi(24)(Bi(3+),Mn(4+))(2)O(40) phase in the (1 - x)Bi(3+)(24)Bi(3+)(2)(O(39)ⁱ(1)) - x(Bi(3+)(24)Mn(4+)(2)O(40)) system. Precision X-ray diffraction studies of single crystals of the Bi(24)(Bi,Si,Mn)(2)O(40) general composition show that these sillenites crystallize in space group P23 and not I23 as the Bi(24)Si(2)O(40) phase. The dissymmetrization of sillenite phases is observed for the first time. It is explained by a kinetic (growth) phase transition of the order-disorder type due to population of a crystallographic site by atoms with different crystal-chemical properties and quasi-equilibrium conditions of crystal growth in the course of a hydrothermal synthesis below 400 °C at unequal molar amounts of the starting components in the batch.

Elastic properties of single crystal Bi12SiO20 as a function of pressure and temperature and acoustic attenuation effects in Bi12MO20 (M = Si, Ge and Ti)

“…In stoichiometric sillenites M is tetravalent and the oxygen lattice is fully occupied (x=1, δ=0) (Wiehl et al 2010). The most prominent members of the sillenite family are those with M=Si, Ge, and Ti, which are abbreviated in the following as BSO, BGO, and BTO (Tissot and Lartigue 1988, Yu and Min 2004, Wiehl et al 2010, Melńikova et al 2011, Wiehl et al 2013.…”

“…For example, sillenites are used in devices utilized for optical computing, optical information processing, and high-sensitive photo detectors (Tempel 1993, Filippov et al 2000. Sillenite single crystals exhibit low acoustic wave velocities and are therefore candidates for delay lines in electronic circuits (Melńikova et al 2011). Due to its high photosensitivity BSO can be used as light moduator as well as a crystal for recording and reproducing phase holograms (Melńikova et al 2011).…”

“…Sillenite single crystals exhibit low acoustic wave velocities and are therefore candidates for delay lines in electronic circuits (Melńikova et al 2011). Due to its high photosensitivity BSO can be used as light moduator as well as a crystal for recording and reproducing phase holograms (Melńikova et al 2011).…”

Hydrothermal growths, optical features and first-principles calculations of sillenite-type crystals comprising discrete MO4tetrahedra

“…Other dopants with oxidation states other than four can be incorporated in the tetrahedral sites by oxygen vacancies, partial occupation of the 2a sites by Bi 3+ or Bi 5+ ions, to achieve charge balance. 18,19 In view of the specific valences and coordinated conditions of metal cations, the optical activities of sillenite-type materials were studied frequently. 17,19,20 For instance, Bi 24 Ga 2 O 39 was approved as an efficient photocatalyst for degrading methylene blue, 21 and nanoparticles of some transition-metal doped sillenites were manifested to show strong photochromism and were used to split water photocatalytically.…”

“…18,19 In view of the specific valences and coordinated conditions of metal cations, the optical activities of sillenite-type materials were studied frequently. 17,19,20 For instance, Bi 24 Ga 2 O 39 was approved as an efficient photocatalyst for degrading methylene blue, 21 and nanoparticles of some transition-metal doped sillenites were manifested to show strong photochromism and were used to split water photocatalytically. 1 The frequently used approaches to bulk sillenite crystals are Czochralski (CZ) growth method for congruently melting ones, high-temperature flux method for incongruently melting ones and hydrothermal crystallization for most of them.…”