Local structure, glass transition, structural relaxation, and crystallization of functional oxide glasses investigated by Mössbauer spectroscopy and DTA

• Published in: Journal of materials science. Materials in electronics Vol. 32; no. 19; pp. 23655 - 23689
• Main Authors: Nishida, Tetsuaki, Kubuki, Shiro, Oka, Nobuto
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.10.2021; Springer Nature B.V
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Crystallization; Debye temperature; Distortion; Glass ceramics; Glass transition temperature; Heat treatment; Iron; Isothermal annealing; Low temperature; Materials Science; Metal oxides; Mossbauer spectroscopy; Optical and Electronic Materials; Oxygen; Polyhedra; Quadrupoles; Review; Tellurium dioxide; Temperature
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1007/s10854-021-06855-w

This review paper summarizes early Mössbauer and DTA studies of different oxide glasses containing small amounts of iron (III) or tin (IV) as the probe. A lot of valuable information of the atomic level has been obtained about the role of nonbridging oxygen (NBO), network former (NWF), network modifier (NWM), local network structure, glass transition, structural relaxation, crystallization, etc. Introduction of alkali oxide into iron (III)-containing oxide glass causes a marked decrease in glass transition temperature ( T g ) amounting to 100 °C and a concordant decrease in quadrupole splitting ( Δ ) of Fe III , which reflects decreased distortion of NWF–oxygen polyhedra and formation of NBO. By contrast, introduction of non-alkali oxide into oxide glass causes an increase in T g amounting to more than 100 °C and a concordant increase in Δ , reflecting increased distortion of NWF–oxygen polyhedra in highly cross-linked network. These experimental results led to a discovery of “ T g - Δ rule”, which was consistent with the “ conformer model ” proposed for polymers by Matsuoka and Quan. Debye temperatures ( θ D ) obtained by low-temperature Mössbauer measurements proved to be useful to determine short- and long-range structures of glass and glass ceramics. Isothermal annealing of vanadate glasses at temperatures higher than T g or crystallization temperature ( T c ) causes a “ tunable ” decrease in DC-resistivity from the order of MΩ cm to Ω cm. Introduction of metal oxide with a narrow bandgap ( E g ) is highly effective to increase the conductivity after the annealing. It was proved that “ structural relaxation ” of NWF–oxygen polyhedra and resultant decrease in the activation energy ( E a ) for conduction are responsible for the improved conductivity. Heat treatment of IR-transmitting aluminate, gallate, and tellurite glasses at temperatures higher than T g or T c revealed that crystallization was triggered by the cleavage of NWF–oxygen bonds. These findings will contribute to the development of functional glass and glass ceramics such as smart glass and eco-friendly glass.