Preparation and structure refinement of Eu3+ doped CaMoO4 nanoparticles

The nanoparticles of CaMoO4 : Eu3+ (Eu3+ = 0, 1, 3, 5, 7, 10 at. %) are prepared at low temperature (150 degrees C for 3 h) using urea hydrolysis in ethylene glycol. These are characterized by X-ray diffraction (XRD), infrared spectroscopy (IR) and transmission electron microscopy (TEM). From XRD study, it was found that the solubility limit of Eu3+ ions at the Ca2+ sites is up to 3 at. % and above this, phase segregation occurs. In combination with Rietveld analysis, its crystal structure was found to be tetragonal phase (space group I4(1)/a (88) and Z = 4 (number of CaMoO4 formula units per unit cell). Unit cell parameters and bond distances are calculated. The average crystallite sizes of as-prepared, 500 and 900 degrees C heated samples are found to be 20, 35 and 70 nm, respectively. The lattice strain is found to be 0.003-0.005. From IR study, the bands at 820 and 441 cm(-1) are assigned to asymmetric stretching and bending vibrations of the MoO42- tetrahedron, respectively. From TEM study, the shape of particle was found to be spherical. The high resolution TEM suggests a change in orientation of the crystal on annealing up to 900 degrees C.