Nanocomposites and nanomaterials

Synthesis and luminescence properties of phosphate-molybdate glasses and glass-ceramics doped with Pr3+ and Eu3+ ions
Chornii V.P.1, Boyko V.V.1, Nedilko S.G.1,2, Terebilenko K.V.2, Slobodyanik M.S.2
1 National University of Life and Environmental Sciences of Ukraine, Geroiv Oborony, 15, Kyiv-03041, Ukraine. 
E-mail: vchornii@gmail.com
2 Taras Shevchenko National University of Kyiv, Volodymyrska st., 64/13, Kyiv-01601, Ukraine.

Polymer-based covers greatly affect efficiency and operation time of phosphor-converted white light emitting diodes (pc-WLEDs). It is known that such polymers (e.g. silicone materials) lose their optical characteristics under action of high temperatures and powerful light fluxes. Consequently, light output of WLEDs as well as their color characteristics depend on quality of polymer. There are numerous scientific and technological efforts directed on substitution of polymer in pc-WLEDs for more stable glasses and glass-ceramics. Currently glasses are considered mainly as a binder for phosphors. Thus, such glasses must be transparent in UV and visible spectral range in order to minimize light energy losses. In our opinion, glass or glass-ceramics can play active role in operation of such devices, namely by light absorption/emission processes. The glass can be additively doped with luminescent ions and glass-ceramics can be made on the base of various kind of inorganic phosphors. 
The work was devoted to preparation and studies of structural and luminescence properties of 37.09K2O-31.79P2O5-25.43MoO3-5.69Bi2O3 glass doped with Eu3+ and Pr3+ ions. The glass-ceramics were obtained through adding of KBi(MoO4)2:Eu or KBi(MoO4)2:Pr micro/nanopowders to abovementioned glass composition. The samples were characterized by means of X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), IR and luminescence spectroscopy. The processes of melting and crystallization in the studied systems were analyzed on the base of XRD, EDX and SEM measurements data. Analysis of the obtained results had shown that studied glasses and glass-ceramics are suitable for LED application because they possess orange-red emission related with vitreous host and rare-earth ions inside both amorphous and crystalline regions of the samples.