Glass and anti-glass phase co-existence and structural transitions in bismuth tellurite and bismuth niobium tellurite systems

Influence of barium oxide on glass-forming ability and glass stability of the tellurite–phosphate oxide glasses

“…There are two basic structural units: TeO 4 (trigonal bipyramid), TeO 3 (trigonal pyramid), as well as the intermediate TeO 3?d polyhedron [5,16,22]. In TeO 4 unit, four oxygen atoms are coordinated with one tellurium atom to form a trigonal bipyramid (tbp) with one of the equatorial oxygen positions unoccupied [5,16,23,24]. In the trigonal pyramid structure, there are two bridging oxygen sites and one non-bridging oxygen (NBO) which is a Te = O double bond [5,16,25].…”

Structure of bismuth tellurite and bismuth niobium tellurite glasses and Bi2Te4O11 anti-glass by high energy X-ray diffraction

“…This suggests that the sample is not crystalline but an 'anti-glass' of monoclinic Bi 2 Te 4 O 11 (powder diffraction le #81-1330). 18 The HEXRD data of 20Bi 2 O 3 -80TeO 2 anti-glass sample was rened by Rietveld method using FULLPROF program. The rened XRD pattern of 20BiTe sample is shown in Fig.…”

“…[15][16][17] The cationic order is responsible for producing sharp peak reections in the X-ray and neutron diffraction patterns, while the anionic defects do not allow the phonons to propagate through them for long distances, thus resulting in the broad vibrational (phonon) bands in the Raman and infrared spectra. 18,19 Bismuth tellurite glasses have been studied for their optical and structural properties 13,20 but the information about the short-range and medium-range order of bismuth tellurite glass system is not available. The addition of Nb 2 O 5 in xBi 2 O 3 -(100 À x)TeO 2 system enhances its GFA and produces glass-ceramic samples that contain coexisting glass and anti-glass phases on slow melt-cooling.…”

“…The binary bismuth tellurite system forms glass only at low The melt from the ternary xBi 2 O 3 -xNb 2 O 5 -(100 À 2x) TeO 2 system is reported to form co-existing glass and anti-glass phases by slow melt quench technique. 18 Hence for HEXRD studies on glasses, the glass melt from this system was splat quenched between the two metal plates to obtain thin akes of the samples, so that the formation of anti-glass phase was avoided and purely glassy phase samples were obtained. All the samples were clear, transparent and their amorphous nature was conrmed by the laboratory source X-ray diffraction measurements performed on Bruker D8 Focus X-ray diffractometer using Cu K a1,2 radiation.…”

Structure of strontium tellurite glass, anti-glass and crystalline phases by high-energy X-ray diffraction, reverse Monte Carlo and Rietveld analysis

“…On adding modifiers such as alkali, alkaline earth and transition metal oxides into TeO 2 , bulk glass samples can be prepared easily at a moderate quenching rate of $10 2 K s À1 (El-Mallawany, 2011; Kaur, Kaur et al, 2018; . Several tellurite systems are known to produce anti-glass materials (Burckhardt & Trö mel, 1983;Bertrand et al, 2015;Blasse et al, 1986;Trö mel et al, 1985Trö mel et al, , 1988Gupta & Khanna, 2018;Gupta et al, 2019;Wilding et al, 2016). An anti-glass is a disordered crystalline solid in which the cations (Te 4+ , Bi 3+ , La 3+ , Nb 5+ , Sr 2+ etc.)…”