Journal ArticleDOI
Vibrational Raman Spectra of CaMoO4 and CaWO4 at High Pressures
Malcolm Nicol,Jean F. Durana +1 more
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In this paper, Raman spectra at pressures as high as 40 kbar are reported for the scheelite and previously unknown high pressure phases of CaMoO4 and CaWO4.Abstract:
Raman vibrational spectra at pressures as high as 40 kbar are reported for the scheelite and previously unknown high‐pressure phases of CaMoO4 and CaWO4. The pressure derivatives of the vibrational frequencies, dν / dP, are all between 0.0 and 1.0 cm−1·kbar−1 which is normal for ionic crystals; however, the observed pressure dependences of the frequencies of the internal modes are qualitatively different from those predicted according to Scott's interpretation of the splittings of the scheelite spectra. The appearance of the high‐pressure phases is indicated by splittings of Eg modes at 145 and 797 cm−1 in CaMoO4 and 117 and 797 cm−1 in CaWO4. The spectra of the high‐pressure phases and the dependences of the apparent transition pressures upon orientation of the crystallographic axes relative to the small stress anisotropy in the high‐pressure cell suggest that the high‐pressure phases have structures similar to that of NiWO4.read more
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Raman spectroscopy of monolayer-type oxide catalysts: Supported Mo oxides
TL;DR: In this paper, a monolayer catalysts based on a structural model which assumed spreading of the active oxide over the support surface were investigated by a variety of techniques, conventional bulk sampling techniques as well as by surface-sensitive electron and ion spectroscopies, in an attempt to elucidate the nature of the catalyst surface species, and to study the coordination environment of active metal center(s).
Journal ArticleDOI
High-pressure crystal chemistry of scheelite-type tungstates and molybdates
TL;DR: In this article, the unit-cell parameters and crystal structures of CaWO4(scheelite) and CaMoO4 (powellite) have been determined at several pressures to 5 8 GPa.
Journal ArticleDOI
Pressure effects on the structural and electronic properties of ABX4 scintillating crystals
TL;DR: In this article, the phase behavior of scheelite-structured orthotungstates has been extensively studied up to 50 GPa and different experimental techniques for obtaining reliable data at simultaneously high pressure and high temperature.
Journal ArticleDOI
Electronic structure, growth mechanism and photoluminescence of CaWO4 crystals
Laécio S. Cavalcante,Valeria M. Longo,Júlio C. Sczancoski,Marcio Aurélio Pinheiro Almeida,Alzir A. Batista,José Arana Varela,Marcelo Ornaghi Orlandi,Elson Longo,M. Siu Li +8 more
TL;DR: In this paper, aggregated CaWO4 micro- and nanocrystals were synthesized by the co-precipitation method and processed under microwave-assisted hydrothermal/solvothermal conditions (160 °C for 30 min).
References
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Journal ArticleDOI
Raman Spectra of CaW O 4 , SrW O 4 , CaMo O 4 , and SrMo O 4
S. P. S. Porto,James F. Scott +1 more
TL;DR: The first-order Raman spectra of CaW${\mathrm{O}}_{4}, CaMo${O}µ, SrW$µ and SrMoµ have been obtained as mentioned in this paper, and all theoretically predicted vibrations have been observed.
Journal ArticleDOI
Raman Spectrum of α Quartz at High Pressures
Jean F. Asell,Malcolm Nicol +1 more
TL;DR: Raman spectra of single crystals of α quartz at pressures as high as 40 kbar are reported in this paper, with a probable accuracy of about 20% due to an uncertainty about the pressure scale.
Journal ArticleDOI
Dipole–Dipole Interactions in Tungstates
TL;DR: In this paper, the vibrational spectra of divalent metal tungstates of the form MWO4, where M = Ba, Sr, Ca, or Zn, have been analyzed in terms of dipole-dipole interactions between adjacent tungstate ions.