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Comparison between crystal field effects on the fluorescence spectra of crystalline SmP5O14 and vitreous (Sm2O3)(0.248)(P2O5)(0.752)

Research output: Contribution to journalArticle

  • H M Farok
  • G A Saunders
  • Wilson Poon
  • J Crain
  • H Vass
  • W Honle
  • E Schonherr

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Original languageEnglish
Pages (from-to)2389-2400
Number of pages12
JournalJournal of Materials Science
Volume34
Issue number10
DOIs
Publication statusPublished - 15 May 1999

Abstract

To investigate how the local symmetry of the Sm3+ ion affects the fluorescence of a samarium metaphosphate glass of composition (Sm2O3)(0.248)(P2O5)(0.752), the temperature and pressure dependences of its laser induced fluorescence spectrum are compared with those of a samarium pentaphosphate crystal (SmP5O14). Findings include: (i) The crystal field splitting of the energy levels responsible for fluorescence in SmP5O14 at room temperature is consistent with the local symmetry of oxygen atoms of the phosphate cage around the Sm3+ ions being quite close to cubic - in accord with crystal structure. At 12 K there is a systematic disappearance of the shortest wavelength lines of each fluorescence band attributable to a decreasing population of higher crystal field levels, which are occupied at ambient temperature. (ii) The (Sm2O3)(0.248)(P2O5)(0.752) g lass fluorescence spectrum forms five bands, which can be related to that of the crystal but with inhomogeneous line broadening; the short wavelength edges sharpen at low temperatures, also attributable to a decreasing population of higher crystal field levels at lower temperatures. (iii) The shifts (d lambda/d rho) in the wavelengths of the fluorescence peaks of the SmP5O14 crystal induced by pressure up to 50 kbar in a diamond anvil cell are small but measurable at room temperature, being about +0.03 nm kbar(-1) (+0.3 Angstrom kbar(-1)). Application of pressures up to 50 kbar to the (Sm2O3)(0.248)(P2O5)(0.752) glass did not alter the positions of the bands within the error in the fluorescence wavelength measurements. Neither the SmP5O14 crystal nor the metaphosphate glass showed any indication of undergoing a phase transition up to the highest pressure reached. A low frequency Raman mode has been observed, which softens with reducing temperature, indicating softening of the associated optical mode and suggesting that, like other RP5O14 crystals, SmP5O14 undergoes a ferroelastic phase transition. (C) 1999 Kluwer Academic Publishers.

    Research areas

  • SAMARIUM PHOSPHATE-GLASSES, FERROELASTIC BEHAVIOR, METAPHOSPHATE GLASS, PHASE-TRANSITION, BORATE, EXAFS

ID: 1491612