Crystal Chemistry of High-Temperature Borates

Abstract

In recent years borate-based crystals has attracted substantial interest among the research community. The overall importance of this family of materials is reflected in miscellaneous articles and several reviews that have been published over the years. Crystalline borate materials exhibit numerous interesting physical properties, which make them promising for further practical applications. Diversity of functional characteristics results from their high structural flexibility caused in the linkage of planar/non–planar BO3 groups and BO4 tetrahedra, which can occur as isolated or condensed structural units. This report is a brief review on crystal chemistry and structure features of anhydrous/high-temperature borates. Polymorphism of boron-oxygen radicals has been considered basing on cations’ nature and synthesis conditions. Analysis of the laws governing borates structures and general principles of their systematics was discussed. As a result, an alternative classification of anhydrous compounds has been considered. It is based on four orders of their subdivision: (1) by the variety of anion formers, (2) by the cation charge, (3) by the N = NM:NB, i.e., ratio of metal atoms number to the ratio of boron atoms number (N-factor) value indicating the borate structural type (if it is known), (4) by the cation type and size.

Boron Influence on Defect Structure and Properties of Lithium Niobate Crystals

“…Boron triangles and tetrahedra can be present in isolation or polymerize among themselves through a common oxygen atom [84]. The tendency towards formation of bulky polyanions explains the high viscosity of melts [85]. It is well known that alkali metal oxides are modifiers of the boron-oxygen network of the melt and transfer the boron atom to a four-coordinated state, i.e., [BO 4 ] tetrahedra are formed [85].…”

“…The tendency towards formation of bulky polyanions explains the high viscosity of melts [85]. It is well known that alkali metal oxides are modifiers of the boron-oxygen network of the melt and transfer the boron atom to a four-coordinated state, i.e., [BO 4 ] tetrahedra are formed [85]. When boron-oxygen triangles and tetrahedra are combined, the absolute values of specific negative charges for complex anions decrease monotonically in the series of ortho-, pyro-, meta-, and polyborates.…”

Boron Substructures in Inorganic Borides: Network Topology and Free Space

“…The central role in the topological interrelations belongs to the honeycomb (hcb) motif, which is found in 14 topological types of the framework boron substructures (Figure 6). In eight cases, the existence of this motif is followed by the appearance of icosahedral groups (3,6 4 T3; 4,5,6 3 ,7T5; 4,6 4 T12; 4,6 4 T13; 4 2 ,5,6 7 ,7T1; 4,5 3 ,6 42 ,7 4 ,8T1; 6 11 ,8 3 ,9T1) or their halves (5,6,7T29); in the ubt motif, the boron triangles above and below an hcb hexagon are rotated compared with icosahedron, thus forming cuboctahedral groups. Different direct connections of stacks of corrugated hcb layers result in the 3D crb or 4,5T548 topologies.…”

“…The crystal chemistry of boron always attracted great attention of experimentalists and theoreticians, thanks to the extremely rich diversity of the atomic architectures mostly caused by a unique ability of boron atoms to form structural groups of different composition, size, and extension. − At present, more than one thousand binary and ternary inorganic borides have been obtained, which crystallize in more than 150 different structural types . When describing a boride crystal structure, one assigns it to a certain structure type and characterizes the structural groups composed of boron and/or metal atoms, their mutual arrangement, and coordination polyhedra. − Depending on the composition of the boride, i.e., the B/Me ratio, one can distinguish metal-rich or boron-rich borides .…”

Synthesis, crystal structure, and thermal stability of double borate Na3ErB2O6

“…Borates are considered to be attractive functional materials for non-linear optic and luminescence due to their wide variety of crystal structures, low synthesis temperature, and environmental benignity [1][2][3][4][5][6][7][8][9][10][11][12][13]. Today commercially used nonlinear optical crystals of borates with superior optical properties are β-BaB2O4 [14] and LiB3O5 [15].…”