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Germanate oxides have garnered considerable interest owing to their diverse structural configuration and intriguing properties. Herein, we present a novel niobium germanate crystal, Rb8Nb10Ge6O41, extracted through the process of spontaneous crystallization. It showcases a unique three-dimensional (3D) structural framework composed of one-dimensional (1D) twisted [Nb7O30]∞ chains and isolated [Ge3O9] rings, arising from the divergent polymerized manifestations of [NbO6] and [GeO4] basic building blocks, respectively, marking the first instance of such a topography in germanate materials. Notably, the title compound exhibits exceptional thermal stability up to 1250 °C with a good congruent melting nature. Moreover, it achieves a short ultraviolet edge at 306 nm and a favorable infrared edge cutoff exceeding 6.2 μm, thus indicating a wide transparency window. Additionally, this study elucidates the microscopic birefringence of Rb8Nb10Ge6O41 and clarifies the intricate relationship between its structure and properties. Our findings suggest that the polymerization of distinct structural motifs within a single compound is an effective strategy for exploring novel inorganic materials. [ABSTRACT FROM AUTHOR]

Germanate oxides have been scarcely studied as promising birefringent crystals due to the inherently weak optical anisotropy. Here, a property improvement strategy with synergetic electron distribution and lattice vibration optimization is proposed by introducing tailored functional units of distorted [NbO6] octahedra and antiparallel [GeO4] motifs in germanates. A prospective Cs3Nb5GeO16 (CNGO) crystal exhibits a breakthrough of experimental birefringence (0.19 at 532 nm), the largest value among the available germanate oxides, as well as a wide transparent window and excellent thermal stability up to 1265 °C. Combined density functional theory (DFT) and dipole moment calculations are performed to unveil the underlying physical mechanism of structure–property relationship. These attributes forebode the great potential of CNGO for manipulating polarized light and open a new avenue for innovating birefringent materials with desirable performances. [ABSTRACT FROM AUTHOR]

Borates, as advanced optical materials, have garnered wide interest due to their diverse structural configurations and great potential for applications in the ultraviolet (UV) regions. Herein, we synthesized a new rare-earth borate crystal, namely, K 2 NaYB 2 O 6 , which is classified as one of the ABReB 2 O 6 compounds, where A and B represent alkali metal and Re denotes rare-earth metal. K 2 NaYB 2 O 6 adopts in the monoclinic space group P 2 1 / c (No. 14), showcasing a three-dimensional (3D) framework composed of a planar triangular configuration of [BO 3 ] units and distortive [YO 7 ] polyhedra. Notably, both dihedral angles between distinct [BO 3 ] units reach 79.6°, which represents an unprecedented structural feature in monoclinic ABReB 2 O 6 -type crystals. Moreover, the compound has a short UV absorption edge at around 204 nm, corresponding to a wide band gap of approximately 5.67 eV. Additionally, it possesses a moderate birefringence of 0.028 at 1064 nm. Further analysis utilizing theoretical calculations suggests that the optical behaviors of K 2 NaYB 2 O 6 are mainly governed by its basic structural unit [BO 3 ] triangles and distorted [YO 7 ] polyhedra. These findings enrich the structure chemistry of rare-earth borates and offer valuable insights for the design of optical crystals in the UV wavelength range.

Germanate is garnering increasing attention in the field of optoelectronics owing to its competitive optical transparency and robust stability. Herein, a novel lithium-rich rare-earth germanate, Li 13 YGe 4 O 16 , was fabricated for the first time using a high-temperature solution approach. This compound adopts the asymmetric space group Cmc 2 1 (no. 36), characterized by isolated [YO 6 ] and [GeO 4 ] structural motifs with Li + cations located in the channel. Notably, Li 13 YGe 4 O 16 presents a short ultraviolet cutoff edge at 240 nm, indicative of an enlarged band gap of 4.96 eV and showcases a wide mid-infrared transmission region exceeding 6.0 μm. Moreover, Li 13 YGe 4 O 16 features exceptional thermal stability and moderate second harmonic generation (SHG) intensity. Additionally, a theoretical analysis suggests that the distorted [YO 6 ] octahedra. [GeO 4 ] and [LiO 4 ] tetrahedra play a significant role in the optical activities of Li 13 YGe 4 O 16 . These attributes endow Li 13 YGe 4 O 16 with the potential to serve as a new mid-IR nonlinear optical (NLO) crystal and enrich the structural chemistry of germanates.

Germanate oxides have garnered considerable interest owing to their diverse structural configuration and intriguing properties. Herein, we present a novel niobium germanate crystal, Rb 8 Nb 10 Ge 6 O 41 , extracted through the process of spontaneous crystallization. It showcases a unique three-dimensional (3D) structural framework composed of one-dimensional (1D) twisted [Nb 7 O 30 ] ∞ chains and isolated [Ge 3 O 9 ] rings, arising from the divergent polymerized manifestations of [NbO 6 ] and [GeO 4 ] basic building blocks, respectively, marking the first instance of such a topography in germanate materials. Notably, the title compound exhibits exceptional thermal stability up to 1250 °C with a good congruent melting nature. Moreover, it achieves a short ultraviolet edge at 306 nm and a favorable infrared edge cutoff exceeding 6.2 μm, thus indicating a wide transparency window. Additionally, this study elucidates the microscopic birefringence of Rb 8 Nb 10 Ge 6 O 41 and clarifies the intricate relationship between its structure and properties. Our findings suggest that the polymerization of distinct structural motifs within a single compound is an effective strategy for exploring novel inorganic materials.

Borate materials are of significant interest due to their versatile structural configuration and competitive ultraviolet (UV) transparency range. In this study, we present a novel rare-earth borate crystal, KNa 2 Lu(BO 3 ) 2 , synthesized for the first time through a facile spontaneous crystallization method. It adopts the centrosymmetric space group Pnma (no. 62) and yields a unique three-dimensional (3D) structural network formed by isolated [BO 3 ] plane triangles and distorted [LuO 7 ] polyhedra. This compound displays excellent thermal stability up to ∼990 °C, demonstrating a favorable congruent melting nature. Moreover, KNa 2 Lu(BO 3 ) 2 achieves a notably short UV absorption cutoff at approximately 204 nm, yielding a large band gap of 5.58 eV. Remarkably, it showcases an enlarged birefringence of 0.044 at 1064 nm, implying its potential as a birefringent material. Moreover, density functional theory calculations demonstrate that the optical characteristics are predominantly influenced by fundamental building blocks [BO 3 ] triangles and distorted [LuO 7 ] polyhedra. Our findings demonstrate the potential of KNa 2 Lu(BO 3 ) 2 in the development of a birefringent candidate and enrich the structural chemistry of rare-earth-based borates.

Borate materials continue to command considerable attention due to their remarkable capacity for applications in deep ultraviolet (UV) wavelengths. Herein, two new metal borates KSrM 3 B 2 O 9 (M = Al and Ga) were extracted via the application of flux techniques. These two crystals adopt a centrosymmetric space group P 2 1 / c (no. 14), showcasing a layered structural configuration composed of isolated [BO 3 ] plane triangles and [AlO 4 ]/[GaO 4 ] tetrahedra. Thermal analysis revealed that KSrM 3 B 2 O 9 (M = Al and Ga) exhibits an incongruent nature and possesses good thermal stability up to 1083 and 983 °C, respectively. Notably, these compounds display a short UV-transmission cutoff edge, approximately around 194 and 200 nm, accompanied by band gaps of 5.47 and 4.83 eV, respectively. Furthermore, KSrM 3 B 2 O 9 (M = Al and Ga) demonstrates a moderate optical birefringence of 0.026 and 0.025, respectively. Additionally, first-principles calculations were employed to shed light on the intricate interplay between the structure and properties of these compounds.

Nonlinear optical (NLO) materials have recently aroused great interest owing to their capability of frequency conversion in solid-state lasers. Herein, we report an acentric zinc germanate K 2 ZnGe 2 O 6 obtained successfully through spontaneous crystallization methods. It affords a novel three-dimensional (3D) framework comprised of [GeO 4 ] and [ZnO 4 ] motifs with K atoms located in the tunnels. K 2 ZnGe 2 O 6 displays a moderate second-harmonic-generation (SHG) intensity (0.73 × KDP) with phase-matchable behavior. Optical characterization demonstrated that it has a UV cutoff edge located at 368 nm with a large energy band of 3.23 eV, accompanied by a wide transmission window, covering a 3-5 μm atmospheric window. Moreover, thermal properties implied that it possesses intriguing thermal stability of 987 °C and a congruent melting nature. Additionally, first-principles calculations unveiled that the NLO performance was primarily attributed to the collective effect of [GeO 4 ] and [ZnO 4 ] building units. These findings indicate that K 2 ZnGe 2 O 6 is a potential NLO crystal.

Molybdate oxide materials have attracted considerable academic interest owing to their multifunctional optoelectronic properties and applications. However, to date, studies on the intrinsic properties of multiple molybdates have rarely been implemented. Herein, a prospective triple molybdate crystal, Rb 3 LiZn 2 (MoO 4 ) 4 , with high crystalline quality was successfully grown using top-seeded solution growth (TSSG) approaches. Intriguingly, it affords a cage-like structure with the I 4̅3 d space group, analogous to that of Ca 12 Al 14 O 33 (C12A7). The Rb 3 LiZn 2 (MoO 4 ) 4 crystal exhibits excellent thermal stability up to 603 °C, accompanied by a congruent melting nature. Simultaneously, it preserves the optical merits of a large band gap of 4.10 eV and a wide transmission window of 0.29-5.4 μm, which are superior to those of most molybdate crystals. More importantly, Raman spectroscopic measurements demonstrated that the title compound possesses an intense Raman shift located at 925 cm -1 and narrow line width, facilitating a stimulated Raman laser. In addition, first-principles calculations were also implemented to elucidate the structure-property relationships of Rb 3 LiZn 2 (MoO 4 ) 4 . These observations provide an empirical platform for intuitively comprehending the underlying properties of multiple molybdates and pave the way for exploiting Raman crystals.

A quaternary nonlinear-optical (NLO) zinc germanate, Rb 2 ZnGe 2 O 6 (RZGO), was prepared from its stoichiometric melts, which belongs to the noncentrosymmetric space group C 222 1 (No. 20) and features a 3D framework formed by GeO 4 tetrahedra, ZnO 4 tetrahedra, and Rb + cations filling into the void space. RZGO displays a good phase-matchable second-harmonic-generation (SHG) intensity similar to that of KH 2 PO 4 . The UV cutoff edge for RZGO was found to be approximately 0.37 μm with a broad optical band gap of 3.22 eV, indicating a large laser-induced damage threshold. Further characterizations suggested that this compound displays an excellent thermal stability (1014 °C) and melts congruently. Besides, theoretical analysis was also implemented to investigate the electronic structures and effective NLO coefficients as well as the origin of the observed SHG response for RZGO. The present study can enrich the diversity of acentric germanate structures and pave the way for the synthesis of new NLO compounds.