Structure cristalline du bromoborate Ca2B5O9Br

Luminescent Inorganic Mixed borate phosphors materials for lighting

The need of new materials with desirable optical properties has become important in recent year. In particular, a need has emerged for compounds having better luminescent properties in various practical applications. Introduction of rare earth ions as activators improves the luminescence properties of the compounds considerably. Boron is one of the most abundant elements in the nature. It readily combines with almost all other elements. In combination with oxygen; it forms borates comprising of various anions like BO₃ ^3- , B₂ O₅ ^4- , etc. Apart from these simple borates, several complex compositions exist involving mixed anions as well as double metal borates. Due to three-fold, or four-fold coordination of borate atoms Borates intrinsically possess characteristics that are advantageous for optical materials, which include wide transparency range, large electronic band gap, good thermal and chemical stability, low preparative temperature, optical stability with good nonlinear characteristics and exceptionally high optical damage threshold. The unique crystal structure of borates determines their enhanced UV transparency, good nonlinearity and relatively high resistance against laser induced damage. Some of these complex borates showing interesting luminescence properties are covered in this review. These include double borates containing rare earths RM₃ (BO₃ )₄ , Pentaborates LaMgB₅ O₁₀ , M₃ R₂ (BO₃ )₄ , where M is alkaline earth, mixed anion borates like aluminoborate SrAl₂ B₂ O₇ , Silicate-Borates like pekovite, SrB₂ Si₂ O₈ , Haloborates, M₂ B₅ O₉ X, where M is alkaline earth and X is halogen, phosphate borates, MBPO₅ , where M is alkaline earth. Phosphors base on these compositions find use in various applications like fluorescent lamps, colour TV, plasma display panels, high intensity discharge lamps based on Xenon, optically pumped solid state lasers, eye safe lasers, X-ray imaging.

A 119Sn Mössbauer-spectroscopic characterization of the diamagnetic birefringence material Sn2B5O9Cl

The crystal structure of diamagnetic borate chloride Sn2B5O9Cl exhibits two crystallographically independent tin sites which both show pronounced lone-pair activity of the tin atoms. This is reflected in substantial quadrupole splitting in the 119Sn Mössbauer spectrum. The isomer shifts of 3.887(8) and 4.137(7) mm s−1 clearly indicate divalent tin. In agreement with bond valence calculations, the Sn1 atoms have a lower charge and the higher isomer shift, compatible with a higher electron density at the tin nuclei.

Hierarchical Ba2(B5O9)Cl·(H2O)0.5 microspheres: surfactant-assisted facile hydrothermal synthesis, Tb3+ doping and photoluminescence properties

Uniform hierarchical Ba₂(B₅O₉)Cl·(H₂O)_0.5 microspheres containing nanorod-like sub-units were synthesized via a mild EDTA-2Na assisted hydrothermal process, which were manifested as great potential green-emitting host materials via Tb³⁺ doping.