X-ray diffraction study on the short-range structure of K2O–TeO2 glasses and melts

Evolution of local structure in Ag2O–TeO2 glasses with addition of Ag2O analyzed by pulsed neutron diffraction and Raman spectroscopy

“…The results suggest that the tellurite glasses having lower Ag 2 O content possessed networks composed of mainly TeO 4 trigonal bipyramids (tbp). These findings were consistent with the alkali tellurite glasses previously reported [21].…”

Alkali environments in tellurite glasses

“…The local structure of alkali M2O-TeO2 glasses (M = Li, Na, and K) has been studied extensively using neutron diffraction [1][2][3][4][5], X-ray diffraction [6,7], EXAFS [7,8], Raman scattering [7,9,10], NMR [2,[11][12][13] and RMC modelling [2,14]. In these studies, particular emphasis was placed on determining the local environment of tellurium and there is a general consensus that the average tellurium coordination number, nTeO, decreases as an oxide modifier is added to the glass network, the change being driven by the bonding requirements of the modifier.…”

Terminal Oxygens in Amorphous TeO2

“…However, tellurite glasses containing modifier oxides (e.g., x K 2 O·(100 – x )TeO 2 ) are easy to produce in bulk quantities and exhibit a number of properties, such as high refractive indexes, third-order NLO coefficients, near-infrared transmittance, and good chemical durability, that make them promising candidates as components in a range of optical devices. To this end, many diffraction, Raman, and NMR studies ,,− have been carried out to characterize the structure of a wide range of tellurite glasses, and it is generally accepted that the tellurium coordination number, n TeO , changes with modifier content. This is not uncommon; both boron and germanium increase their coordination number to accommodate modifier oxide in a manner that roughly follows that in the analogous crystal structures. , Therefore, it seems reasonable to use the structure of alkali tellurite crystals as the basis of a model for tellurite glass structures .…”

“…Therefore, unlike a typical tetrahedral environment, α-TeO 2 is comprised of asymmetric [TeO 4 ] units with two short (1.882 Å) equatorial and two long (2.117 Å) axial Te–O bonds (Figure a) . Diffraction studies show that tellurite glasses have an even wider distribution of Te–O bond lengths, which is both broad and asymmetric. − As a result, determining the exact extent of Te–O bonds is problematic, and coordination numbers (especially those derived from experiments with poor real-space resolution, such as EXAFS and early diffraction measurements) are inexact. However, with the advent of high-resolution time-of-flight neutron diffraction instruments, total scattering measurements can produce correlation functions, T ( r ), which yield accurate coordination numbers; for example, our recent study of α-TeO 2 gives a value for n TeO of 3.95(3) ( n OTe = 1.98(1)), while a measurement of amorphous GeO 2 gave n GeO = 4.02(3) .…”