Co-substitution design: a new glaserite-type rare-earth phosphate K2RbSc(PO4)2 with high structural tolerance

An alkali rare-earth phosphate K2RbSc(PO4)2 was successfully obtained as a derivative of glaserite-type K3Na(SO4)2 by co-substitution of K(1)O12 → RbO12, K(2)O10 → KO7, NaO6 → ScO6 and SO4 → PO4, while maintaining the original anionic framework. K2RbSc(PO4)2 exhibits a layered [Sc(PO4)2]∞ framework built from ScO6 octahedra and PO4 tetrahedra, with K and Rb residing in the interlayers. Its isostructural lanthanide analogues K2RbEr(PO4)2 and K2RbLu(PO4)2, inspired by an elemental substitution strategy, were also prepared by a high-temperature solid state reaction. The successful substitution indicates that the skeleton of K2RbSc(PO4)2 is stable with high structural tolerance, which can provide a possibility for substitution of resident ions to obtain diverse structural types and applications.

K2Sr4(PO3)10: A Polyphosphate with Deep-UV Cutoff Edge and Enlarged Birefringence

A new polyphosphate K2Sr4(PO3)10 is synthesized by a high-temperature solution method. This compound crystallizes in the triclinic space group of P1̅, consisting of the 1D infinite [PO3]∞ chains and K and Sr ions between the chains. Compared with AM2(PO3)5 (A = K, Rb, Cs; M = Ba, Pb), K2Sr4(PO3)10 exhibits a more complex [PO3]∞ chain structure and more diverse metal cationic coordination environment. More importantly, K2Sr4(PO3)10 has both a deep-UV cutoff edge (<200 nm) and a significantly enlarged birefringence. First-principles calculations indicate that the birefringence of K2Sr4(PO3)10 is 0.017 at 1064 nm, about 2 times that of RbBa2(PO3)5 (0.008 at 1064 nm), which reaches a new height among the reported mixed alkali metal and alkaline earth metal phosphate. Theoretical calculations and structural analyses show that the enlarged birefringence of K2Sr4(PO3)10 mainly originates from the [PO3]∞ chains arranged in an inverted zigzag. This discovery introduces a new strategy for devising novel phosphate deep-UV optical crystals with a large birefringence.

Three diphosphates, α-Li2Na2P2O7, Li8Pb3Ba(P2O7)4 and Li7Rb(P2O7)2: influences of co-substitution on the crystal structure

We reported the synthesis, structure, characterization and first-principles calculations of diphosphates, α-Li₂Na₂P₂O₇, Li₈Pb₃Ba(P₂O₇)₄ and Li₇Rb(P₂O₇)₂, and studied the influences of co-substitution on the crystal structure.

Three non-centrosymmetric bismuth phosphates, Li2ABi(PO4)2 (A = K, Rb, and Cs): effects of cations on the crystal structure and SHG response

We reported the synthesis, structure and nonlinear properties of three phosphates, Li₂ABi(PO₄)₂ (A = K, Rb, and Cs), and the effects of cations on the crystal structure and SHG response.

LiGaP2O7: A Potential UV Nonlinear-Optical Crystal

A new noncentrosymmetric pyrophosphate, LiGaP₂O₇, is designed and synthesized by a reasonable energy-band regulation engineering strategy with isovalent substitution. The title compound crystallizes in the monoclinic space group P2₁ (No. 4) with lattice parameters a = 4.7593(10) Å, b = 7.9586(16) Å, c = 6.8940(14) Å, and Z = 2, which is the isomorphic compound of LiMP₂O₇ (M = Fe, Cr). Compared with LiMP₂O₇, LiGaP₂O₇ exhibits a wide band gap of 4.56 eV due to no d-d electronic transitions. Meanwhile, good phase-matching ability and a moderate second-harmonic-generation (SHG) response in LiGaP₂O₇ are maintained. First-principles calculations of the band structure and nonlinear-optical performance were also performed in order to gain insight into the role of the Ga-O groups in the band gap and SHG effect source.

Structural insights into three phosphates with distinct polyanionic configurations

P–O units are shown to feature distinct polyanionic configurations from [PO₃]_∞ chains to [P₄O₁₂]⁴⁻ rings.

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.

Fluoroborophosphates: a family of potential deep ultraviolet NLO materials

A series of new fluoroborophosphates obtained by combining BO₃F or BO₂F₂ with a PO₄ tetrahedron exhibit short UV absorption edges and display second-harmonic generation signals.

Three new phosphates, Cs8Pb4(P2O7)4, CsLi7(P2O7)2 and LiCa(PO3)3: structural comparison, characterization and theoretical calculation

Three new phosphates with a short cutoff edge were obtained, and the structural comparisons were discussed in detail.

K2SrP4O12: a deep-UV transparent cyclophosphate as a nonlinear optical crystal

Benefiting from high transmittance of PO4 tetrahedra in the deep-ultraviolet (deep-UV) region, phosphates have been investigated as deep-UV nonlinear optical (NLO) candidates for years. So far, reported deep-UV NLO phosphates are orthophosphates and polyphosphates while cyclophosphates, important members of the phosphates family, have usually been neglected for use as deep-UV NLO crystals. Here, we first report a novel cyclotetraphosphate K2SrP4O12 (KSPO) as a deep-UV transparent NLO crystal. In its structure, the fundamental building groups are ring [P4O12]4- groups. KSPO exhibits a moderate second-harmonic generation (SHG) response that is 0.5 times that of KH2PO4 (KDP) and a short deep-ultraviolet absorption edge smaller than 200 nm.

Two new tin(iv)-containing phosphate fluorides with two types of Sn(iv)–P–O–F frameworks and short cutoff edges

Two new [SnOF] groups connect with the [P–O] group to form interesting structures.

Experimental characterization and first principles calculations of linear and nonlinear optical properties of two orthophosphates A3Al2(PO4)3 (A = Rb, K)

We report the experimental characterization and first principles calculation of linear and nonlinear optical properties of two orthophosphates A₃Al₂(PO₄)₃ (A = Rb, K).

Modulation of perovskite-related frameworks induced by alkaline earth metals in phosphate fluorides A2MPO4F (A = K, Rb; M = Ba, Ca)

A₂CaPO₄F (A = K, Rb) are isomorphs. The 1D zig-zag [FA₄Ca₂]_∞ chains in the two compounds belong to the 1D perovskite-related structure.

Insights of BO3–PO4 replacement for the design and synthesis of a new borate–phosphate with unique 1∞[Zn4BO11] chains and two new phosphates

A borate–phosphate CsZn₄(BO₃)(PO₄)₂ and two phosphates CsZn₄(PO₄)₃ and RbZn₄(PO₄)₃ were obtained via BO₃–PO₄ replacement, and the substitution of BO₃–PO₄ is a feasible strategy for preparing new compounds.

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.

Syntheses, structures and properties of metal phosphates Pb2Mg(PO4)2, Pb4Zn8(PO4)8 and α-BaZn2(PO4)2

Pb₂Mg(PO₄)₂, Pb₄Zn₈(PO₄)₈ and α-BaZn₂(PO₄)₂ have been synthesized by the standard solid-state reaction and their structures were determined by single crystal X-ray diffraction for the first time. Pb₂Mg(PO₄)₂, Pb₄Zn₈(PO₄)₈ and α-BaZn₂(PO₄)₂ crystallize in the monoclinic crystal system, P2₁/c, C2/c and the trigonal crystal system, P3[combining macron]m1, respectively. The structure of Pb₂Mg(PO₄)₂ possesses a three-dimensional framework consisting of MgO₆ octahedra and PO₄ tetrahedra and the Pb²⁺ cations reside in the [Mg₆P₆O₁₂] tunnels. Pb₄Zn₈(PO₄)₈ and α-BaZn₂(PO₄)₂ are two-dimensional layered structures with [Zn₄P₄O₁₆]_∞ layers for Pb₄Zn₈(PO₄)₈ and [Zn₃P₃O₁₂]_∞ honeycomb double layers for α-BaZn₂(PO₄)₂. And in the structure of Pb₄Zn₈(PO₄)₈, there are four different Zn-P-O layers, which is reported for the first time in zinc phosphates. In addition, thermal property analysis, and UV-Vis-NIR diffuse reflectance and infrared spectroscopy were also performed. First-principles theoretical studies were also conducted to aid the understanding of their band structures and densities of states.

Low-temperature-flux syntheses of ultraviolet-transparent borophosphates Na4MB2P3O13 (M = Rb, Cs) exhibiting a second-harmonic generation response

The first non-centrosymmetric mixed-alkali-metal borophosphates, Na₄MB₂P₃O₁₃ (M = Rb 1, Cs 2), were obtained using a low-temperature flux method. Single-crystal X-ray diffraction studies of 1 and 2 reveal that the two compounds are isostructural, both crystallizing in the orthorhombic space group Pna2₁; their structures consist of novel 1D borophosphate chains constructed from B₂P₃O₁₄ fundamental building units, assembled into a 3D framework by alkali metal cations. Second-harmonic generation (SHG) measurements show that 1 and 2 are type-I phase-matchable, with SHG responses ca. 0.35 and 0.42 times that of KH₂PO₄, respectively. The cut-off edges of 1 and 2 are ca. 276 and 267 nm, respectively, which suggests that they are potential ultraviolet nonlinear optical materials. Density functional theory calculations were employed to shed light on the band structure and density of states as well as the electron density distribution.

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.

Experimental and theoretical studies on the linear and nonlinear optical properties of lead phosphate crystals LiPbPO4

LiPbPO₄achieved a desired balance between UV transparency (232 nm) and high nonlinear optical (NLO) activity (about 3 × KDP).