Yttrium and rare-earth modified lithium orthoborates: Glass formation and vibrational activity

The dual role of bismuth in Li2O–Bi2O3–B2O3 glasses along the orthoborate join

“…The 11 B MAS NMR spectrum of the YBO 3 reference material also reveals a BO 3 quantity on the order of a few percent, indicating residual hightemperature phase (BO 3 3− structures) from the synthesis. The IR absorption coefficient spectrum from a previous study of the same material 23 does indeed show very weak F I G U R E 5 Deconvoluted 11 B MAS NMR spectra of crystalline reference materials. Measured spectra are in black, and the fitted model is the dashed red line.…”

“…As previously mentioned in Section 1, our recent work 23 demonstrated the possibility of preparing a pseudo-binary lithium orthoborate-containing carbonate species left over F I G U R E 2 Glass formation along the orthoborate tie-line in the ternary lithium-bismuth borate system from the decomposition of the starting materials. Without the presence of residual carbonate, the pure binary melt crystallizes upon cooling despite our best effort.…”

“…Samples from compositions x = 10, 20, 30, and 40 were subjected to 1-h long heat treatments at corresponding temperatures of 385, 465, 500, and 570 • C. Crystalline lithium orthoborate was prepared by melting the stoichiometric mixture at 1150 • C for 15 min then allowing the material to cool in air. Crystalline Bi 3 B 5 O 12 was prepared by melting a glass of the same composition before devitrifying via a thermal treatment at 550 • C for 18 h. 20 Crystalline YBO 3 is used as a reference material; this sample was previously synthesized and studied by X-ray diffraction, Raman, and IR spectroscopy by Topper et al 23,32 Another reference material used in this study is an impurity-stabilized bismuthate glass that was obtained by melting Bi 2 O 3 in a Colorado clay crucible at 1150 • C for 90 min.…”

“…Recently, a pseudo-binary lithium orthoborate glass was produced, assisted by the retention of carbonate species intentionally preserved by a short melting time of the 3Li 2 CO 3 -1B 2 O 3 batch. 23 Borate speciation therein consisted of only BO 3 3− units. When yttrium oxide was added and the orthoborate tie-line was traversed toward YBO 3 , the short-range order was unaffected by the addition of up to 30 mol% Y 2 O 3 .…”

“…These observations of borate tetrahedra with non-bridging oxygen (NBO) atoms are in contrast to the traditional viewpoint of borate glass network modification, which holds that above the metaborate space (O:B = 2:1), trigonal borate species become increasingly depolymerized and tetrahedral borate species only exist with all bridging oxygen atoms, that is, the metaborate type [BØ 4 ] − (Figure 1). Reports of orthoborate isomerization 28 and disproportionation 29 first appeared in fairly isolated records; however, multiple structural studies in the most recent decade have supported these initial assessments, 16,23,[25][26][27]30 though a consensus has yet to be reached throughout the glass science community.…”