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RESEARCH PRODUCT
Low-temperature polymorphism in tungsten trioxide powders and its dependence on mechanical treatments
J. PuransEnzo CazzanelliAlexei KuzminClaudio VinegoniGino Mariottosubject
Phase transitionChemistrylow-temperature polymorphismAnalytical chemistryTemperature cyclingTriclinic crystal systemCondensed Matter PhysicsTungsten trioxideElectronic Optical and Magnetic MaterialsInorganic ChemistryNanocrystalline tungsten trioxide powderschemistry.chemical_compoundCrystallographysymbols.namesakePolymorphism (materials science)X-ray crystallographyNanocrystalline tungsten trioxide powders low-temperature polymorphism mechanical treatments Raman spectroscopyRaman spectroscopyMaterials ChemistryCeramics and CompositessymbolsPhysical and Theoretical Chemistrymechanical treatmentsRaman spectroscopyMonoclinic crystal systemdescription
The polymorphism of WO3 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 di⁄raction. A transition from the monoclinic (I) c-phase to the triclinic d-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 e-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 lowtemperature N-phase has been observed below about 200 K in di⁄erent samples: it is the main phase in commercial untreated powders, having the monoclinic (I) c-phase at room temperature, but constitutes only a small fraction in moderately treated powders, having the triclinic d-phase at room temperature. ( 1999 Academic Press
| year | journal | country | edition | language |
|---|---|---|---|---|
| 1999-02-01 |