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A high-quality Cr 3+:CdWO4 single crystal at a size of approximatelyΦ25×80 mm is grown using the Bridgman method with CdO,WO3,and Cr2O3 as raw materials and their molar ratio of 100:100:0.5.The temperature gradient of solid-liquid interface at growth is approximately 50?C/cm and the growth rate is 0.05 mm/h.The X-ray diffraction(XRD),absorption,excitation,and emission spectra of different parts of the as-grown and O2-annealed crystals are investigated.Two strong broad optical absorption bands of about 472 and 708 nm are observed,and they are associated with the transitions 4 A2→ 4 T1 and 4 A2→ 4 T2.The weak 4 T2→ 2 E transition(the R-line)at 632 nm is also observed.The crystal-field parameter Dq and the Racah parameters B and C are estimated to be 1 412.4,776.8,and 3 427.6 cm? 1,respectively,according to the absorption spectra and crystal-splitting theory.A broadband fluorescence at about 1 000 nm due to 4 T2→ 4 A2 transition is produced by exciting the samples at 675 nm.After being annealed in an O2 atmosphere,the crystals become more transparent,while the effective light absorption of Cr 3+ ions is evidently enhanced and the emission intensity is also strengthened due to the reduction of oxygen vacancies in the CdWO4 crystal after annealing.
A high-quality Cr 3+: CdWO 4 single crystal at a size of approximately Φ25 × 80 mm is grown using the Bridgman method with CdO, WO 3, and Cr 2 O 3 as raw materials and their molar ratio of 100: 100: 0.5. The temperature gradient of solid-liquid interface at growth is approximately 50? C / cm and the growth rate is 0.05 mm / h. X-ray diffraction (XRD), absorption, excitation, and emission spectra of different parts of the as-grown and O2- annealed crystals are investigated. Two strong broad optical absorption bands of about 472 and 708 nm are observed, and they are associated with the transitions 4 A2 → 4 T1 and 4 A2 → 4 T2. The weak 4 T2 → 2 E transition (the R -line) at 632 nm is also observed. The crystal-field parameter Dq and the Racah parameters B and C are estimated to be 1 412.4, 776.8, and 3 427.6 cm -1, respectively, according to the absorption spectra and crystal-splitting theory. A broadband fluorescence at about 1 000 nm due to 4 T2 → 4 A2 transition is produced by exciting the samples at 675 nm. Afte r being annealed in an O2 atmosphere, the crystals become more transparent, while the effective light absorption of Cr 3+ ions is evidently enhanced and the emission intensity is also due due to the reduction of oxygen vacancies in the CdWO4 crystal after annealing.