Synthesis and characterization of mixed alkali borophosphate with a new 1D chain: Li3Cs2BP4O14

Variable dimensionality of the anion framework in four new borophosphates and fluoroborophosphates with short cutoff edges

Two new borophosphates, Cs₃B₃P₄O₁₆ and Li(NH₄)₂B₃P₄O₁₆, and two new fluoroborophosphates, K₄B₂P₂O₉F₂ and Rb₃B₂PO₅F₄, have been obtained via the high-temperature solution method. Single-crystal X-ray diffraction indicates that all of them exhibit various anion frameworks although they crystallize in the same space group, P2₁/c. Two-dimensional (2D) [B₃P₄O₁₆]_∞ layers and a 3D [B₃P₄O₁₆]_∞ network can be found in Cs₃B₃P₄O₁₆ and Li(NH₄)₂B₃P₄O₁₆, respectively, while isolated [B₂P₂O₉F₂] and [B₂PO₅F₄] exist in K₄B₂P₂O₉F₂ and Rb₃B₂PO₅F₄, respectively. The effect of the alkali metal cation size on the framework structures of Cs₃B₃P₄O₁₆ and Li(NH₄)₂B₃P₄O₁₆ has been discussed in detail. The IR spectra confirm their structural validity. UV-Vis-NIR diffuse reflectance spectroscopy indicates that the new compounds exhibit short cutoff edges. In addition, theoretical calculations were carried out to understand their electronic structures and optical properties.

Synthesis, crystal structure and luminescence properties of a new samarium borate phosphate, CsNa2Sm2(BO3)(PO4)2

A new caesium sodium samarium borate phosphate, CsNa₂Sm₂(BO₃)(PO₄)₂, has been obtained successfully by the high-temperature solution growth (HTSG) method and single-crystal X-ray diffraction analysis reveals that it crystallizes in the orthorhombic space group Cmcm. The structure contains BO₃, PO₄, NaO₇ and SmO₇ polyhedra which are interconnected via corner- or edge-sharing O atoms to form a three-dimensional [Na₂Sm₂(BO₃)(PO₄)₂]_∞ network. This network delimits large cavities where large Cs⁺ cations reside to form the total structure. Under 402 nm light excitation, CsNa₂Sm₂(BO₃)(PO₄)₂ exhibits three emission bands due to the 4f→4f transitions of Sm³⁺. Furthermore, we introduced Gd³⁺ into Sm³⁺ sites to optimize the Sm³⁺ concentration and improve the luminescence intensity. The optimal concentration is Gd/Sm = 98/2. The luminescent lifetime of a series of CsNa₂Gd_2(1-x)Sm_2x(BO₃)(PO₄)₂ phosphors shows a gradual degradation of lifetime from 2.196 to 0.872 ms for x = 0.01-0.10. The Commission Internationale de l'Eclairage (CIE) 1931 calculation reveals that CsNa₂Gd_1.96Sm_0.04(BO₃)(PO₄)₂ can emit orange light under 402 nm excitation.

Design, synthesis, crystal structure and luminescent properties introduced by Eu3+ of a new type of rare-earth borophosphate CsNa2REE2(BO3)(PO4)2 (REE = Y, Gd)

The rich compositional and structural diversity of borophosphates provides a wide variety of host lattices for luminescent materials. Herein, we report a borophosphate, CsNa₂REE₂(BO₃)(PO₄)₂ (REE = Y, Gd), with a new type of three-dimensional (3D) anionic framework of [REE₂(BO₃)(PO₄)₂]_∞. In this structure, REE³⁺ ions are in a linear array and the nearest intraline REE-REE distance is above 6.9 Å. Surprisingly, the Eu³⁺ activated phosphors CsNa₂REE_2(1-x)Eu_2x(BO₃)(PO₄)₂ show an insignificant concentration quenching effect; the higher the Eu³⁺ concentration, the larger the absolute luminescent external quantum yield. The 100% Eu³⁺ phosphor CsNa₂Eu₂(BO₃)(PO₄)₂ possesses an IQY of 59% under 394 nm excitation. Moreover, CsNa₂Eu₂(BO₃)(PO₄)₂ phosphor possesses superior thermal stability in the range 30-200 °C, retaining more than 96% of its initial intensity at 200 °C. We believe the prepared phosphor has potential application as a red phosphor for NUV excited LEDs.

K2TeP2O8: a new telluro-phosphate with a pentagonal Te–P–O layer structure

We report a new telluro-phosphate K₂TeP₂O₈ with an analogously pentagonal [TeP₂O₈]²⁻ layer structure.