Luminescence and luminescence excitation under VUV radiation of ABP 2 O 7 (A = Na, K, Cs; B = Al, In) double phosphates are studied. Two emission bands peaking near 330 and 420 nm are common for investigated ABP 2 O 7 crystals. The band structure and partial densities of electronic states of perfect KAlP 2 O 7 , LiInP 2 O 7 and NaTiP 2 O 7 crystals are calculated by the full-potential linear-augmented-plane-wave (FLAPW) method. It is found that the structures of the conduction bands of ABP 2 O 7 crystals, which have different B cations, are appreciably different. Experimental results are compared with results of calculations of the electronic structure. Assumptions concerning the origin of luminescence in double phosphates are made.
PACS 77.84.Bw, 78.55.Hx Sodium titanium orthophosphate NaTi 2 (PO 4 ) 3 crystals were synthesized and their luminescence properties were investigated. Luminescence spectra of this compound consist of two main bands in the green and red spectral regions. Maximum positions of the bands depend on temperature of the samples. At some conditions the red band reveals details of a fine spectra structure. Obtained results are discussed taking into account similarity of spectral properties of the investigated crystals with ones described recently for sodium aluminum diphosphate crystals doped with chromium ions. Conclusion is made that red emission band is corresponded to radiation transitions in the Ti 3+ titanium ions.
The La1‑xEuxVO4 powders were synthesized by co-precipitation method. Emission spectra of the LaEuVO4 and La1‑xEuxVO4 powders consist of wide non-structural bands of the matrix emission and narrow spectral lines caused by inner f-f electron transitions in the Eu3+ ions, respectively. The both types of emission were studied within 8 – 300 K temperature range. Decomposition of spectra of the wide matrix emission on three bands has been carried out and temperature dependencies for each band were studied. Temperature behavior of the Eu3+ emission was investigated for lines assigned to different Eu3+ centres. Obtained dependencies are analyzed and discussed using proposed schemes of transitions in the VO43- groups and structure of the nearest surrounding of the Eu3+ emission centres.
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