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- Osada, M., et al.
(författare)
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In situ resonant Raman scattering and reversible photoinduced structural change in YBa2Cu3O6+x
- 2005
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 71
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Tidskriftsartikel (refereegranskat)abstract
- We report on bidirectional photoswitching associated with the CuO chains in oxygen-deficient YBa2Cu3O6+x single crystals. By varying the wavelength of light polarized along the CuO chains, the material can be reversibly switched between two metastable states characterized by the existence or absence of a specific Raman scattering resonance. A comparison of the spectral efficiencies for this photoswitching with analogous data for the persistent photoconductivity and photoconductivity quenching effects suggests that the two phenomena have the same microscopic origin. We argue that the effects are due to photoinduced Cu-O charge-transfer excitations, which destabilize chains of different length depending on wavelength, and promote the growth of thermally inaccessible oxygen ordering configurations.
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| 6. |
- Frantti, J, et al.
(författare)
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Raman scattering study of the Pb(HfxTi1-x)O-3 ceramics
- 2005
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Ingår i: Journal of Electroceramics. - 1573-8663 .- 1385-3449. ; 13, s. 299-303
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Tidskriftsartikel (refereegranskat)abstract
- Raman spectroscopy was used to study the long wavelength vibrations of tetragonal perovskite (space group P4mm) Pb(HfxTi1-x)O-3 (PHT) (0.10 less than or equal to x less than or equal to 0.50) samples at room temperature and at approximate to 20 K. For x less than or equal to 0.40, Raman spectra collected from the PHT samples were very similar to the previous spectra collected from the PZT samples with the same value of x, except the mode at around 190 cm(-1) whose frequency was decreasing with increasing x in PHT ceramics. Correspondingly, the latter feature was taken as a sign of the 'mass effect' (Hf versus Zr) while the similarity of the remaining parts of the Raman spectra was assumed to be due to the almost identical ionic radii difference between Ti4+ and Zr4+ and between Ti4+ and Hf4+ ionic radii. The behaviour of the mode at around 280 cm(-1) revealed that a phase transition occurred once x was changing from 0.40 to 0.50.
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