Claudio Vinegoni, Ph.D. | Low-temperature polymorphism in tungsten trioxide powders and its dependence on mechanical treatments

J. Solid State Chem.
Low-temperature polymorphism in tungsten trioxide powders and its dependence on mechanical treatments

Cazzanelli, E., Vinegoni, C., Mariotto^#, G., Kuzmin, A., and Purans, J.

Journal of Solid State Chemistry 1999

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The polymorphism of WO, powder samples, resulting from mild mechanical treatments and from temperature changes between 30 K and room temperature, has been investigated by using Raman spectroscopy and X-ray diffraction. A transition from the monoclinic (I) gamma-phase to the triclinic delta-phase after moderate mechanical treatments has been observed for untreated powder, just what happens when the same samples are rapidly cooled to low-temperature. Evidences of the low temperature monoclinic (II) polar epsilon-phase have been found at room temperature in samples after a stronger milling treatment. The sequence of the low-temperature phase transitions appears to be strongly dependent on the mechanical history of the powders. A new low-temperature N-phase has been observed below about 200 K in different samples: it is the main phase in commercial untreated powders, having the monoclinic (I) gamma-phase at room temperature, but constitutes only a small fraction in moderately treated powders, having the triclinic delta-phase at room temperature. (C) 1999 Academic Press.
@article{1999-JSSC, author= {Cazzanelli, E. and Vinegoni, C. and Mariotto<sup>#</sup>, G. and Kuzmin, A. and Purans, J.}, title= {Low-temperature polymorphism in tungsten trioxide powders and its dependence on mechanical treatments}, journal= {Journal of Solid State Chemistry}, alternatejournal = {J. Solid State Chem.}, year = {1999}, volume = {143}, number = {1}, pages = {24-32}, issn = {0022-4596}, doi = {10.1006/jssc.1998.8061}, }
10.1006/jssc.1998.8061

Abstract

"The polymorphism of WO, powder samples, resulting from mild mechanical treatments and from temperature changes between 30 K and room temperature, has been investigated by using Raman spectroscopy and X-ray diffraction. A transition from the monoclinic (I) gamma-phase to the triclinic delta-phase after moderate mechanical treatments has been observed for untreated powder, just what happens when the same samples are rapidly cooled to low-temperature. Evidences of the low temperature monoclinic (II) polar epsilon-phase have been found at room temperature in samples after a stronger milling treatment. The sequence of the low-temperature phase transitions appears to be strongly dependent on the mechanical history of the powders. A new low-temperature N-phase has been observed below about 200 K in different samples: it is the main phase in commercial untreated powders, having the monoclinic (I) gamma-phase at room temperature, but constitutes only a small fraction in moderately treated powders, having the triclinic delta-phase at room temperature. (C) 1999 Academic Press."

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For attribution in academic contexts, please cite this work as:

Cazzanelli, E., Vinegoni, C., Mariotto^#, G., Kuzmin, A., & Purans, J. (1999). Low-temperature polymorphism in tungsten trioxide powders and its dependence on mechanical treatments. Journal of Solid State Chemistry, 143(1), 24–32. https://doi.org/10.1006/jssc.1998.8061