High-pressure Syntheses and Characterization of the Rare Earth Borates RE5(BO₃)₂F₉ (RE=Dy, Ho)

Abstract

The new rare earth fluoride borates RE 5 (BO 3) 2 F 9 (RE = Ho, Dy) were synthesized under highpressure/high-temperature conditions of 1.5 GPa, 1250 • C for Dy 5 (BO 3) 2 F 9 and 2.5 GPa, 1200 • C for Ho 5 (BO 3) 2 F 9 in a Walker-type multianvil apparatus from the corresponding rare earth oxides, rare earth fluorides, and boron oxide. The single-crystal structure determinations have revealed that both compounds are isotypic to the known rare earth fluoride borates RE 5 (BO 3) 2 F 9 (RE = Er, Tm, Yb). The new fluoride borates crystallize monoclinically in the space group C2/c (Z = 4) with the lattice parameters a = 2046.7(4), b = 615.9(2), c = 829.6(2) pm, β = 100.1(1) • for Dy 5 (BO 3) 2 F 9 and a = 2039.5(4), b = 612.7(2), c = 827.1(2) pm, β = 100.2(1) • for Ho 5 (BO 3) 2 F 9. Three crystallographically different nine-fold coordinated rare earth cations can be identified in the crystal structure. All boron atoms build up isolated trigonal-planar [BO 3 ] 3− groups. In addition to the Raman and IR spectroscopic investigations, DFT-calculations were performed to support the assignment of the vibrational bands.

Raman spectral probe on increased local vibrational modes and phonon lifetimes in Ho3+-doped Bi2O3micro-rods

“… In the present study, it is evident that Ho doping enhances some phonon vibrational modes of Bi 2 O 3 as well as the appearance of some of the Ho‐related vibrational peaks (LVM). The additional peaks centered at 595 and 925 cm −1 have been assigned to the stretching vibrations of Ho–O–Ho (s Ho–O–Ho) and stretching vibration of Bi–O − , respectively (s Bi–O) . Even though none of the crystalline Bi 2 O 3 polymorph has a peak at 925 cm −1 , the doped samples may contain amorphous or glassy regions.…”

The synthesis of novel lanthanum hydroxyborate at extreme conditions

“…The positional disorder of the BO 3 groups is unusual for known RE borates and has never been described before. In terms of a three-fold coordinated boron atom, in RE borates BO 3 group can form either linked chains [for example, in α-Sm(BO 3 ) 2 ( Fuchs et al, 2020a ) or in LaB 2 O 4 F ( Hinteregger et al, 2013b )], or isolated triangles [for instance, in NdBO 3 ( Müller-Bunz et al, 2003 ) or in Dy 5 (BO 3 ) 2 F 9 ( Hinteregger et al, 2013a )]. The arrangement of boron groups in most cases is coplanar (parallel to one plane) or slightly distorted.…”

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.…”