The Flexibility of P2O7 Dimers in Soft Structures: M2CdP2O7 (M = Rb, Cs)

Cadmium phosphates with two types of fundamental building units and a wide ultraviolet transparency window

Owing to diverse crystal structures and intriguing properties, metal phosphates have attracted much attention in recent studies. In this work, two cadmium phosphates, KCd₆P₇O₂₄ and KCd₃P₃O₁₁, were obtained by the high-temperature solution method. In the crystal structure, both the title compounds contain two types of P-O fundamental building units. Thermal and spectral analyses were carried out on the title compounds, indicating that both of them have good thermal stability and short UV cut-off edges. In addition, the relationship between the electronic structures and optical properties was studied by theoretical calculations.

Growth, Structure and Optical Characterization of Rb3Ti3P5O20 Single Crystal

Phosphate crystals attract much attention on account of their rich crystal structures and excellent physical and chemical properties. Herein, Rb3Ti3P5O20 single crystals were grown by the high temperature solution method using Rb2CO3 and NH4H2PO4 as the fluxes. This crystal, with non-centrosymmetric Pca21 space group, presents a three-dimensional framework structure composed of [TiO6] octahedron, [PO4] tetrahedra, and [P2O7] dimers. The electronic structure was measured via X-ray photoelectron spectroscopy. The measurements found that Rb3Ti3P5O20 has stronger Ti–O ionic bonding properties and weaker P–O covalent bonding properties compared to RbTiOPO4. Optical measurements indicated that Rb3Ti3P5O20 has a 3.54 eV band gap and a wide transmission range (0.33–4.5 μm). Theoretical calculations showed that Rb3Ti3P5O20 crystals have a moderate birefringence of 0.079 at 1064 nm. In addition, the relationship of the structure–property was studied using first-principles method. The results demonstrated that TiO6 octahedron played a significant role for the optical properties.

A new diphosphate Ba2LiGa(P2O7)2: synthesis, crystal structure and Eu3+-activated fluorescence performance

This work presents a new diphosphate Ba₂LiGa(P₂O₇)₂ with an anionic [LiGa(P₂O₇)₂]_∞ framework that is constructed from P₂O₇, LiO₅ and GaO₆ groups. Eu³⁺-doped Ba_2−xLiGa(P₂O₇)₂:xEu³⁺ (x = 0.05–0.3) samples show intense red photoluminescence emission.

Na3Sm(PO4)2: (3+1)-dimensional commensurately modulated structure model and photoluminescence properties

For the first time, we determined the detailed crystal structure of Na3Sm(PO4)2 using single crystal X-ray diffraction and established the commensurately modulated structure model using the superspace formalism. The structure adopts a (3+1)-dimensional superspace group Pca21(0β0)000 with the modulation vector q=1/3b*. At the same time, the photoluminescent properties of Na3Sm(PO4)2 sintered at different temperatures between 800 and 1200°C were studied. Under near-UV excitation (402 nm), Na3Sm(PO4)2 shows intense characteristic emission bands of Sm3+ (561, 596, 642 nm) with the CIE coordinate of (0.5709, 0.4282), corresponding to orange color. The excitation spectrum covers a wide range from 350 nm to 470 nm, which indicates that Na3Sm(PO4)2 can be efficiently activated by near-UV or visuable LED ship.

Syntheses, crystal structures and photoluminescence properties of two rare-earth molybdates CsLn(MoO4)2 (Ln=Eu, Tb)

Single crystals of two cesium rare-earth molybdates CsLn(MoO4)2 (Ln=Eu, Tb) have been prepared using the high temperature molten salt (flux) method. Single-crystal X-ray diffraction analyses reveal that they crystallize in the orthorhombic space group Pccm (No. 49) and features a 2D layer structure that is composed of [Ln(MoO4)2]∞ and [Cs]∞ layers. Under near-UV light excitation, emission spectrum of CsEu(MoO4)2 consists of several sharp lines due to the characteristic electronic transitions of Eu3+ ions, whereas CsTb(MoO4)2 exhibits characteristic green emission of Tb3+ ions.

Structure comparison and optical properties of Na7Mg4.5(P2O7)4: a sodium magnesium phosphate with isolated P2O7 units

The crystal structure of Na₇Mg_4.5(P₂O₇)₄ comprises a parallelogram channel composed of corner/edge-sharing isolated [P₂O₇] dimers and a Na(2)O₅ polyhedra to form a 3D framework and has an ultraviolet (UV) cut-off edge of about 210 nm.