RE₄B₄O₁₁F₂ (RE = Pr, Nd): Two New Rare-earth Fluoride Borates Isotypic to Gd₄B₄O₁₁F₂

Abstract

The rare-earth fluoride borates RE 4 B 4 O 11 F 2 (RE = Pr, Nd) were obtained in a Walkertype multianvil device from the corresponding rare-earth oxides and fluorides, and boron oxide. Pr 4 B 4 O 11 F 2 was obtained under high-pressure/high-temperature conditions of 8.5 GPa/1150 • C, and Nd 4 B 4 O 11 F 2 at 8 GPa and 1300 • C. The single-crystal structure determinations revealed that both compounds are isotypic to RE 4 B 4 O 11 F 2 (RE = Eu, Gd, Dy), crystallizing in the space group C2/c (Z = 4) with the parameters a = 1397.3(3), b = 472.78(9), c = 1400.2(3) pm, β = 91.1(1) • , V = 0.9248(3) nm 3 , R 1 = 0.0444, and wR 2 = 0.0539 (all data) for Pr 4 B 4 O 11 F 2 , and a = 1389.1(3), b = 471.2(1), c = 1394.4(3) pm, β = 91.1(1) • , V = 0.9125(3) nm 3 , R 1 = 0.0286, and wR 2 = 0.0601 (all data) for Nd 4 B 4 O 11 F 2. The structure type of Gd 4 B 4 O 11 F 2 contains BO 4 tetrahedra as well as BO 3 groups connected via common corners. Here, we report about the crystallographic characterization of both compounds in comparison to the isotypic phases and discuss their IR spectra.

Rare-Earth Scandium Borate Fluoride with a Deep-Ultraviolet Cutoff Edge

“…However, there have been only 33 cases of reported anhydrous rare-earth borate fluorides so far. It is important to note that many rare-earth borate fluorides, such as LnB 2 O 4 F (Ln = La, Ce), a series of RE 4 B 4 O 11 F 2 and RE 5 (BO 3 ) 2 F 9 compounds, are synthesized under conditions of high temperature and high pressure. – This is because the high reaction temperature of rare-earth oxides makes it difficult to react fully at normal pressure and maintain the existence of F simultaneously. Therefore, considering that alkali metal fluorides can be used as fluorine sources and have relatively low melting points, we intend to lower the reaction temperature of the system by choosing appropriate alkali metal fluorides as the reactants and fluxes.…”

High‐Pressure Synthesis and Crystal Structure of the Highly Condensed Yttrium Borate YB7O12

“…The presence of these different structural groups and connections between them enriched by threefold-coordinated oxygen atoms makes it difficult to find a quantitative parameter for the comparison of these borates with respect to a degree of condensation expressed by the ratio B/O. However, concerning high-pressure borates which are exclusively built up from corner-sharing BO 4 tetrahedra, our efforts resulted in highly condensed compounds like -MB 4 O 7 (M = Mn-Zn) [5] and RE 2 B 8 O 15 (RE = La, Pr, Nd) [6] possessing a degree of condensation of B/O = 0.57 and 0.53, respectively. These values are quite high in comparison to the highest reachable value of 0.66 in the high-pressure modification of boron oxide B 2 O 3 -II, [7] which is exclusively built up from corner-sharing BO 4 tetrahedra including threefold coordinated oxygen atoms.…”