Nanocomposites and nanomaterials

Synthesis and optical properties of luminescent 
molybdate glass-ceramics
Chornii V.P.1,2, Nedilko S.G.1, Terebilenko K.V.1, Slobodyanik M.S.1, Teselko P.O.1, Boyko V.V.2, Pan’ko O.P.2
1 Taras Shevchenko National University of Kyiv. Volodymyrska st., 64/13, Kyiv-01601, Ukraine 
E-mail: snedilko@univ.kiev.ua
2 National University of Life and Environmental Sciences of Ukraine. Geroiv Oborony st., 15, Kyiv-03041, Ukraine 

The transparent glass-ceramics (GC) attracts great attention due to necessity to substitute silicone-based phosphor converters for manufacturing of high-power white light emitting diodes. This kind of composite materials possesses the host property like glass and retains the optical performance of micro/nanocrystaline phosphors. The latter ones are actively elaborated on the base of doped with rare-earth ions molybdate and phosphate compounds. It can be assumed that the glass and crystalline constitutes should have similar refractive indices in case of their similar chemical composition. Consequently, the GC should have higher optical homogeneity and possess small internal light scattering when both components have similar chemical nature. Moreover, this light scattering can be lower when the nanosized phosphors are used in GC. This work deals with synthesis and optical characterization of transparent luminescent phosphate-molybdate glass and GC. 
The sets of pure and Eu3+-doped glasses of 37.09K2O-31.79P2O5-25.43MoO3-5.69Bi2O3 composition and the glass-ceramic consisting of abovementioned glass and KBi(MoO4)2:0.05Eu micro/nanophosphor have been prepared by fast cooling of the molten salts. The samples have been characterized by means of optical, SEM and scanning force microscopy. The X-ray powder diffraction, IR and luminescence spectroscopy have been also applied under study. 
The photoluminescence spectra of the un-doped glasses consist of wide two-component band with maxima near 580 and 660 nm. The peaks of the 5D0→7F2 radiation transitions in the Eu3+ ions dominates in the PL spectra of Eu - doped glasses and glass ceramics when the PL was excited in the 250 – 560 nm spectral range and at room temperature. The most intensive band in the PL excitation spectra corresponds to the 7F0→5D2 electronic transitions in Eu3+ ions. The results have showed that studied glasses and compositions are perspective for elaboration of oxide glass-ceramic materials of good luminescence characteristics.