Alkali environments in tellurite glasses

Abstract

Neutron diffraction measurements are reported for five binary alkali tellurite glasses, xM2O·(100-x)TeO2 (containing 10 and 20 mol% K2O, 10 and 19 mol% Na2O, and 20 mol% 7 Li2O), together with 23 Na MAS NMR measurements for the sodium containing glasses.Differences between neutron correlation functions are used to extract information about the local environments of lithium and sodium. The Na-O bond length is 2.37(1) Å and the average Na-O coordination number, nNaO, decreases from 5.2(2) for x=10 mol% Na2O to 4.6(1) for x=19 mol% Na2O. The average Li-O coordination number, nLiO, is 3.9(1) for the glass with x=20 mol% Li2O and the Li-O bond length is 2.078(2) Å. As x increases from 10 to 19 mol% Na2O, the 23 Na MAS NMR peak moves downfield, confirming an earlier report of a correlation of peak position with sodium coordination number. The close agreement of the maximum in the Te-O bond distribution for sodium and potassium tellurite glasses of the same composition, coupled with the extraction of reasonable alkali coordination numbers using isostoichiometric differences, gives strong evidence that the tellurium environment in alkali tellurites is independent of the size of the modifier cation used.

Tellurium Vanadate Glasses: V4+colorimetric Measure and Its Effect on Conductivity

“…Previous research (Dimitriev et al, 1983;Barney et al, 2015) shows the binary tellurium vanadate glasses do indeed contain vanadium ions in two states: V 4+ and V 5+ . As such, these glasses meet the general condition that TMIs be present in more than one valence state, and exploring this ratio is key to determining why these glasses display the conductivity they do.…”

Nano Crystallites and Clustered Species in Modified Sodium Telluride Glasses

“…The latter type of bonds interconnects the neighboring chains via very asymmetric Te-O terminal -Te. The bending vibrations of those bonds account for the band near 660 cm -1 [1][2][3][4][5][6]. ) showed a gradual increase.…”

“…The structure of binary and ternary telluride glasses [1][2][3][4][5] has been investigated extensively by a variety of experimental techniques [5,6]. It has been reported that the structure of TeO 2 glasses with a small amount of Na 2 O (up to 20 moles %) is a continuous random network of TeO 4 trigonal bipyramids (tbps) and TeO 3+1 polyhedra having one nonbridging oxygen, NBO.…”

“…The spectrum for the as prepared pure vitreous TeO 2 is also shown (figure 4) for comparison. The spectrum of pure TeO 2 glass ( figure 4) is dominated by several diffraction peaks which may be assigned to ordered TeO 2 network made of chain -like fragments, consisting of the rather symmetric Te-O-Te bridges and Te-O terminal bonds[1][2][3][4][5][6][7]. The more ordered structure is disrupted to great extend by adding Na 2 O in the region (20-35 mol %),figure 3(a, b)and then recrystallization is appeared again at higher Na 2 O concentration.…”

Thermal and microstructural characterization and crystallization kinetic studies in the TeO2−B2O3 system

“…Later, Bürger et al [12] studied the glass forming region, phase equilibria and structural investigation of the system and revised the phase diagram. Apart from these studies, Kashchieva et al [15] carried out transmission electron microscope investigations in the system, Halimah et al [16] studied physical properties, Sabry et al [13] studied optical and electrical properties of boro-tellurite glasses and Barney et al [17] realized structural investigation of the TeO 2 eB 2 O 3 system.…”