The Luminescence of CdWO<sub>4</sub>:Tb,Li Crystals under Synchrotron Excitation at 10 K

Novosad, S. S.; Kostyk, L.; Novosad, I. S.; Luchechko, A.; Stryganyuk, G.

doi:10.12693/aphyspola.122.717

Cited by 2 publications

(3 citation statements)

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“…The crystal structure is severely reorganized at the phase transition, which is also expressed in a strong broadening of the single crystal reflections in the highpressure phase. At the phase transition, the oxygen coordinations of cadmium and tungsten cations are increased from [6] to [6+1] and [7], respectively (Fig. 1).…”

Section: B X-ray Diffractionmentioning

confidence: 99%

“…It possesses a high light yield emission when hit by γ particles or x-rays and despite its long scintillation time (12-15 µs) 4 , it played a key role in the discovery 5 of the natural alpha activity in 180 W. Also, the long decay time of the radiation created by self-trapped Frenkel excitons of CdWO 4 makes this material a test bench for studying excitonexciton interactions in semiconductors 6 . In order to improve the versatility of CdWO 4 as a scintillating material, understanding how doping 7 or externally modifying its interatomic distances affect its electronic structure, are of interest. In this context, pressure is an efficient tool to correlate changes in the bond distances with electronic properties.…”

Section: Introductionmentioning

confidence: 99%

“…The symmetry changes from space group P 2/c in the low-pressure wolframite phase to P 21/c in the highpressure post-wolframite phase accompanied by a doubling of the unit-cell volume. The octahedral oxygen coordination of the tungsten and cadmium ions is increased to [7]-fold and [6+1]-fold, respectively, at the phase transition. The compressibility of the low-pressure phase of CdWO4 has been reevaluated with powder x-ray diffraction up to 15 GPa finding a bulk modulus of B0 = 123 GPa.…”

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confidence: 99%

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Optical and structural study of the pressure-induced phase transition of CdWO4

et al. 2017

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The optical absorption of CdWO4 is reported at high pressures up to 23 GPa. The onset of a phase transition was detected at 19.5 GPa, in good agreement with a previous Raman spectroscopy study. The crystal structure of the high-pressure phase of CdWO4 was solved at 22 GPa employing single-crystal synchrotron x-ray diffraction. The symmetry changes from space group P 2/c in the low-pressure wolframite phase to P 21/c in the highpressure post-wolframite phase accompanied by a doubling of the unit-cell volume. The octahedral oxygen coordination of the tungsten and cadmium ions is increased to [7]-fold and [6+1]-fold, respectively, at the phase transition. The compressibility of the low-pressure phase of CdWO4 has been reevaluated with powder x-ray diffraction up to 15 GPa finding a bulk modulus of B0 = 123 GPa. The direct band gap of the low-pressure phase increases with compression up to 16.9 GPa at 12 meV/GPa. At this point an indirect band gap crosses the direct band gap and decreases at -2 meV/GPa up to 19.5 GPa where the phase transition starts. At the phase transition the band gap collapses by 0.7 eV and another direct band gap decreases at -50 meV/GPa up to the maximum measured pressure. The structural stability of the post-wolframite structure is confirmed by ab initio calculations finding the post-wolframite-type phase to be more stable than the wolframite at 18 GPa. Lattice dynamic calculations based on space group P 21/c explain well the Raman-active modes previously measured in the high-pressure post-wolframite phase. The pressure-induced band gap crossing in the wolframite phase as well as the pressure dependence of the direct band gap in the high-pressure phase are further discussed with respect to the calculations.

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Section: B X-ray Diffractionmentioning

confidence: 99%