New investigations within the TeO2-WO3 system : phase equilibrium diagram and glass crystallization

• Published in: Journal of materials science Vol. 34; no. 17; pp. 4285 - 4292
• Main Authors: BLANCHANDIN, S, MARCHET, P, THOMAS, P, CHAMPARNAUD-MESJARD, J. C, FRIT, B, CHAGRAOUI, A
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer 01-01-1999; Springer Nature B.V
• Subjects: Air quenching; Binary system; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Crystallization; Differential scanning calorimetry; Disordered solids; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Fluorite; Glass transition temperature; Glass transitions; Glasses; Investigations; Materials science; Phase diagrams; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Phase diagrams of other materials; Phase equilibria; Physics; Specific phase transitions; Structure of solids and liquids; crystallography; Tellurium dioxide; Tungsten oxides; Unit cell; X-ray diffraction; Phase diagrams; Inorganic compounds; Transition element compounds; Crystallization; Glass; Binary systems; Tungsten oxides; XRD; Experimental study; Tellurium oxides; DSC; Glass transformations; Phase equilibria
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1023/A:1004667223028

The TeO2-WO3 pseudo-binary system was investigated by temperature programmed X-ray diffraction and differential scanning calorimetry (DSC). The investigated samples were prepared by air quenching of totally or partially melted mixes of TeO2 and WO3. Glass forming compositions were identified by X-ray diffraction on quenched samples. Glass transition and crystallization temperatures were measured by DSC. The identification of the compounds appearing during glass crystallization revealed two new metastable compounds. The first one, which appears both for low WO3 content and pure TeO2 glasses, was attributed unambiguously to a new TeO2 polymorph called γ. This one irreversibly transforms into the stable α-TeO2 form, at about 510 °C. It crystallizes with the orthorhombic symmetry and unit cell parameters a = 0.8453(3) nm, b = 0.4994(2) nm, c = 0.4302(2) nm, Z = 4. The second compound was detected for samples containing about 5 to 10 WO3 mol %. It is cubic (F mode, a = 0.569 nm, Z = 4) and seems to have a fluorite-like structure. In addition, phase equilibrium diagram was determined. This binary system appears to be a true binary eutectic one.