NaCa₅BO₃(SiO₄)₂ with Interesting Isolated [BO₃] and [SiO₄] Units in Alkali- and Alkaline-Earth-Metal Borosilicates

Abstract

A new borosilicate, NaCa 5 BO 3 (SiO 4 ) 2 , has been synthesized by a high-temperature solution method, which crystallizes in the centrosymmetric monoclinic space group P2 1 /c (No. 14), having a tangled three-dimensional (3D) network including isolated [BO 3 ] triangles, isolated [SiO 4 ] tetrahedra, and [CaO n ] (n = 7−9) and [NaO 7 ] polyhedra. According to our surveys, it is the first compound containing both isolated [BO 3 ] triangles and isolated [SiO 4 ] tetrahedra in alkali-and alkaline-earth-metal borosilicates, which enriches the structure chemistry of borosilicates. The UV−vis−NIR diffuse reflectance spectrum shows that NaCa 5 BO 3 (SiO 4 ) 2 exhibits a wide transparent region which covers the near-IR, visible, and UV windows and displays a short UV cutoff edge at about 240 nm. Additionally, the thermal behavior (TG and DSC) and IR spectrum were also analyzed. For a deeper understanding of the relationships between the structure and properties, an analysis of theoretical calculations by density functional theory was also performed.

Cd8(BO3)4SiO4: Metal Cation Inducing the Formation of Isolated [BO3] and [SiO4] Units in Borate Silicate

“…Moreover, higher temperatures are beneficial for the synthesis of compounds entirely based on the isolated [BO 3 ] and [SiO 4 ] units. NaSr 5 (BO 3 )­(SiO 4 ) 2 , NaCa 5 BO 3 (SiO 4 ) 2 , and as described Cd 8 (BO 3 ) 4 SiO 4 were all synthesized over 850 °C. In addition, for the compounds with the low molar ratio of M/(B + Si) (<1), the large B/Si ratio (>1) makes it possible that the basic B–O groups condense to highly polymerized B–O groups when the low B/Si ratio (<1) makes highly polymerized Si–O groups.…”

Borate-Based Compounds as Mixed Polyanion Cathode Materials for Advanced Batteries

“…These other chemistries serve as model phases whose transition metal can be substituted with earth-abundant metals, such as Fe and Ni. Model compounds of BPO [112,126,[192][193][194][195][196][197][198][199][200][201] (Table S1), BSiO [181,202,203] (Table S2), and BSO [185][186][187] (Table S3) with transition metal (M = Co, Mn, Cu, and Zn) compositions are found in the literature. These model phases feature 2D layered and 3D open framework channel-forming structures that can host alkali metal ions either in the interlayers or in the pores or pockets of the structure.…”

Hydrothermal Synthesis and Structural Investigation of a Crystalline Uranyl Borosilicate

“…The simplified underlying net of the borosilicate chain topology is shown in Figure 2b. A variety of borosilicate units have been observed in non-uranyl compounds [31][32][33][34][35][36]; to the best of our knowledge, K 1.8 Na Within the larger voids of the [(UO 2 )BSi 4 O 12 ] 3− framework, K + cations are disordered over three sites that have a combined total occupancy of one, whereas the smaller channels contain disordered Na + /K + cations located on a single site staggered between UO 6 octahedra, with occupancies of Na + and K + refining to 0.61 and 0.39, respectively. It was expected that larger alkali cations could be incorporated into the structure considering the extensive disorder of the K + cations in the large channels of the framework; however, attempts to synthesize the Rb and Cs analogs were unsuccessful.…”

“…While uranyl borosilicates are relevant to waste form applications, in the case of non-actinide borosilicates, the structural diversity afforded by the presence of the borosilicate units often promotes the formation of noncentrosymmetric structures, making some of these compounds potentially promising candidates as nonlinear optical materials [30]. Some of the known examples within these compound classes contain isolated BO 3 and SiO 4 structural units [31,32], condensed BO 4 and SiO 4 tetrahedra [33,34], trigonal planar BO 3 units condensed with tetrahedral BO 4 and SiO 4 [35], as well as HBO 4 and SiO 4 hydroxyborosilicate units [36].…”