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Four new phosphites/phosphates, namely Al[P2O3(OH)3](H2O), Al[(HPO3)(OH)(H2O)], Ca[HPO3] and Al3P6O19.5, were designed and synthesized by low temperature flux methods. They crystallized in P63mc, P1¯, P43212, and P63/m space groups, respectively. The basic units of Al[P2O3(OH)3](H2O), Al[(HPO3)(OH)(H2O)] and Ca[HPO3] are composed of [PO3]3− or/and [AlO6]9− groups, whereas the structure of Al3P6O19.5 is built from [PO4]3− tetrahedra and [AlO6]9− octahedra. The structure of Al[P2O3(OH)3](H2O) features a two-dimensional (2D) layered motif of Al[P2O3(OH)3]. Meanwhile, Al[(HPO3)(OH)(H2O)] has high porosity and relatively large channels, and has an excellent molecular sieve structure. Both Al[P2O3(OH)3](H2O) and Al[(HPO3)(OH)(H2O)] display deep ultraviolet (UV) cut-off edges of ∼195 nm and ∼193 nm. The three-dimensional (3D) structure of Al3P6O19.5 is formed by [Al2O9] dimers connected with six PO4 tetrahedra, and one PO4 tetrahedron linked three [Al2O9] dimers alternately. Importantly, Ca[HPO3] shows a moderate second harmonic generation (SHG) effect with a short UV cut-off edge of ∼192 nm in the deep-UV region. The syntheses and topological structures of Al[P2O3(OH)3](H2O), Al[(HPO3)(OH)(H2O)], Ca[HPO3] and Al3P6O19.5, together with some related properties, such as nonlinear optical (NLO) properties, elemental analysis, thermal stability, infrared spectroscopy, Raman spectroscopy and UV-vis diffuse reflectance spectroscopy, are also discussed. [ABSTRACT FROM AUTHOR]

Two novel alkali metal aluminophosphates, namely, Li3[Al(PO4)2(H2O)1.5] and Na[AlP2O7], were synthesized through low-temperature flux methods. They crystallized in the P4 and C2/c space groups, respectively. Both structures of Li3[Al(PO4)2(H2O)1.5] and Na[AlP2O7] were built up by AlO6 octahedra and PO4 tetrahedra. The structure of Li3[Al(PO4)2(H2O)1.5] was composed of novel two-dimensional (2D) aluminophosphate layers, which contained two types of eight-membered rings (8-MRs) along the c-axis. The structure of Na[AlP2O7] featured a unique 3D anionic framework composed of corner-sharing isolated AlO6 octahedra and PO4 tetrahedra. Three intersecting tunnels along the [001], [110], and [101] directions could be observed. Importantly, the material Li3[Al(PO4)2(H2O)1.5] crystallized in the polar space group P4, showing a moderate second-harmonic generation (SHG) effect. Moreover, Na[AlP2O7] exhibited a wide transparency range with a short ultraviolet (UV) cut-off edge (∼190 nm), which indicated its potential application in the deep-UV region. Herein, the syntheses and topological structures of Li3[Al(PO4)2(H2O)1.5] and Na[AlP2O7], as well as elemental analysis, thermal stability, infrared spectroscopy, UV-vis diffuse reflectance, structural properties, and nonlinear optical (NLO) properties are also discussed. [ABSTRACT FROM AUTHOR]

A novel polymorph of ThB2O5, denoted as β-ThB2O5, was synthesised under high-temperature high-pressure (HT/HP) conditions. Via single crystal X-ray diffraction measurements, β-ThB2O5 was found to form a three-dimensional (3D) framework structure where thorium atoms are ten-fold oxygen coordinated forming tetra-capped trigonal prisms. The only other known polymorph of ThB2O5, denoted α, synthesised herein using a known borax, B2O3–Na2B4O7, high temperature solid method, was found to transform to the β polymorph when exposed to conditions of 4 GPa and ∼900 °C. Compared to the α polymorph, β-ThB2O5 has smaller molar volume by approximately 12%. Exposing a mixture of the α and β polymorphs to HT/HP conditions ex situ further demonstrated the preferred higher-pressure phase being β, with no α phase material being observed via Rietveld refinements against laboratory X-ray powder diffraction (PXRD) measurements. In situ heating PXRD measurements on α-ThB2O5 from RT to 1030 °C indicated that α-ThB2O5 transforms to the β variant at approximately 900 °C via a 1st order mechanism. β-ThB2O5 was found to exist only over a narrow temperature range, decomposing above 1050 °C. Ab initio calculations using density functional theory (DFT) with the Hubbard U parameter indicated, consistent with experimental observations, that β is both the preferred phase at higher temperatures and high pressures. Interestingly, it was found by switching from B2O3–Na2B4O7 to H3BO3–Li2CO3 flux using consistent high temperature solid state conditions for the synthesis of the α variant, β-ThB2O5 could be generated. Comparison of their single crystal measurements showed this was identical to that obtained from HT/HP conditions. [ABSTRACT FROM AUTHOR]

A novel polymorph of ThB2O5, denoted as β-ThB2O5, was synthesised under high-temperature high-pressure (HT/HP) conditions. Via single crystal X-ray diffraction measurements, β-ThB2O5 was found to form a three-dimensional (3D) framework structure where thorium atoms are ten-fold oxygen coordinated forming tetra-capped trigonal prisms. The only other known polymorph of ThB2O5, denoted α, synthesised herein using a known borax, B2O3–Na2B4O7, high temperature solid method, was found to transform to the β polymorph when exposed to conditions of 4 GPa and ∼900 °C. Compared to the α polymorph, β-ThB2O5 has smaller molar volume by approximately 12%. Exposing a mixture of the α and β polymorphs to HT/HP conditions ex situ further demonstrated the preferred higher-pressure phase being β, with no α phase material being observed via Rietveld refinements against laboratory X-ray powder diffraction (PXRD) measurements. In situ heating PXRD measurements on α-ThB2O5 from RT to 1030 °C indicated that α-ThB2O5 transforms to the β variant at approximately 900 °C via a 1st order mechanism. β-ThB2O5 was found to exist only over a narrow temperature range, decomposing above 1050 °C. Ab initio calculations using density functional theory (DFT) with the Hubbard U parameter indicated, consistent with experimental observations, that β is both the preferred phase at higher temperatures and high pressures. Interestingly, it was found by switching from B2O3–Na2B4O7 to H3BO3–Li2CO3 flux using consistent high temperature solid state conditions for the synthesis of the α variant, β-ThB2O5 could be generated. Comparison of their single crystal measurements showed this was identical to that obtained from HT/HP conditions. [ABSTRACT FROM AUTHOR]

Crystals of three novel highly porous aluminophosphates, namely, α-NaAlPO4(OH) (1), β-NaAlPO4(OH) (2) and Al3.5P5.5O19 (3), were synthesized through mild hydrothermal methods. Interestingly, among these three porous aluminophosphates, 1 is polar, whereas the other compounds are nonpolar and centrosymmetric. The 3D framework structure of 1 is built from AlO6 octahedra and isolated PO4 tetrahedra. 1D Al-chains are linked by PO4 tetrahedra via sharing corners, forming the 3D framework, and 1D 8-membered ring (MR) tunnels were observed along the c-axis. Importantly, the material of 1 exhibits a moderate second harmonic generation (SHG) effect. 2 features a unique 3D anionic framework composed of corner-sharing [Al2O11] dimers and isolated PO4 tetrahedra. Three intersecting tunnels along the axes can be observed; the small tunnels along the c-axis are based on 4-MRs, whereas the two 6-MRs are along the a- and b-axes. The structure of 3 displays a unique 3D framework based upon face-sharing [Al2O9] dimers and isolated PO4 tetrahedra. The small tunnels along the a- and b-axes are based upon 4-MRs, whereas the 1D larger tunnels are based on 12-MRs along the c-axis. Here, the syntheses and topological structures of α-NaAlPO4(OH) (1), β-NaAlPO4(OH) (2) and Al3.5P5.5O19 (3) as well as their elemental analysis, thermal stability, infrared spectroscopy, UV-vis diffuse reflectance and nonlinear optical (NLO) properties are also reported. [ABSTRACT FROM AUTHOR]

A novel polymorph of ThB 2 O 5 , denoted as β-ThB 2 O 5 , was synthesised under high-temperature high-pressure (HT/HP) conditions. Via single crystal X-ray diffraction measurements, β-ThB 2 O 5 was found to form a three-dimensional (3D) framework structure where thorium atoms are ten-fold oxygen coordinated forming tetra-capped trigonal prisms. The only other known polymorph of ThB 2 O 5 , denoted α, synthesised herein using a known borax, B 2 O 3 -Na 2 B 4 O 7 , high temperature solid method, was found to transform to the β polymorph when exposed to conditions of 4 GPa and ∼900 °C. Compared to the α polymorph, β-ThB 2 O 5 has smaller molar volume by approximately 12%. Exposing a mixture of the α and β polymorphs to HT/HP conditions ex situ further demonstrated the preferred higher-pressure phase being β, with no α phase material being observed via Rietveld refinements against laboratory X-ray powder diffraction (PXRD) measurements. In situ heating PXRD measurements on α-ThB 2 O 5 from RT to 1030 °C indicated that α-ThB 2 O 5 transforms to the β variant at approximately 900 °C via a 1st order mechanism. β-ThB 2 O 5 was found to exist only over a narrow temperature range, decomposing above 1050 °C. Ab initio calculations using density functional theory (DFT) with the Hubbard U parameter indicated, consistent with experimental observations, that β is both the preferred phase at higher temperatures and high pressures. Interestingly, it was found by switching from B 2 O 3 -Na 2 B 4 O 7 to H 3 BO 3 -Li 2 CO 3 flux using consistent high temperature solid state conditions for the synthesis of the α variant, β-ThB 2 O 5 could be generated. Comparison of their single crystal measurements showed this was identical to that obtained from HT/HP conditions.