Synthesis and study of (Ca/Ba)0.45Eu0.05Zr2(PO4)3 nanophosphors and (Ca/ Ba)0.45Eu0.05Zr2(PO4)3@SiO2 nanostructures with blue-green emission

Abstract

M0.45Eu0.05Zr2(PO4)3 nanophosphors with M = Ca or Ba were prepared by a two-steps process including the use of a sol-gel process under basic conditions followed by treatment in a N2/H2 reducing atmosphere. Ca0.45Eu0.05Zr2(PO4)3 sample were also obtained by treatment in a N2 flow. The corresponding M0.45Eu0.05Zr2(PO4)3 @SiO2 nanocomposites were synthetized by treatment with tetraortoethylsilicate (TEOS). The effects of calcium by barium substitution on the samples were analyzed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) and transmission electron microscopy (TEM). TEM-energy dispersive spectroscopy (EDS) analyses were carried

out by using an OXFORD INCA instrument. In addition, magnetic behavior, photoluminescence emission spectra and Commission International de I′Eclairage (CIE) of these phosphors were analyzed by magnetic susceptibility measurements and photoluminescence (PL) spectroscopy, respectively. XRD patterns of synthesized samples can be indexed according to a rhombohedral symmetry of space group R-3 with Z = 6, compatible with a NASICON-type structure. FTIR spectra of the covered samples show some bands attributed to Si-O bending vibration and additional characteristics of vibration modes of PO43- units. Nanoparticles covered by a silica shell were found in TEM micrographs of M0.45Eu0.05Zr2(PO4)3 @SiO2 whose thickness depends on its reaction time with TEOS. Magnetic measurements confirm the state oxidation of europium ions in the all luminescent cores. PL measurements show a variation of the emission intensity related to both the replacement of calcium by barium and the different thicknesses of the silica shell.