Structural and optical characterization of Er-doped CaMoO<sub>4</sub>down-converting phosphors
Puneet Kaur, Rajesh Kumar, Shreya Davessar, Atul Khanna
Abstract
x Er 2 O 3 –(1− x )CaMoO 4 ( x = 1, 3, 5, 7 and 10 mol%) nanoparticles were synthesized by solid-state sintering at 800°C. X-ray diffraction studies confirmed the tetragonal crystal structure of CaMoO 4 , while the doped samples show the co-existence of cubic Er 2 O 3 and tetragonal CaMoO 4 and rule out the replacement of Ca 2+ by Er 3+ in the structure. The crystal unit-cell dimensions, phase concentration and atomic position coordinates were determined by Rietveld refinement. The short-range structure of CaMoO 4 consists of tetrahedral MoO 4 and snub disphenoid deltahedral CaO 8 units, while the unit cell of Er 2 O 3 consists of two types of ErO 6 octahedral units. All MoO 4 units contain Mo—O bonds of equal lengths, whereas two types of slightly different Ca—O bond lengths exist in CaO 8 . Raman spectra of the doped samples show only Mo—O vibrational modes and the Raman peaks of Er 2 O 3 are masked by Mo—O bond vibrations. CaMoO 4 shows bluish-green emission at 500 nm, while Er-doped samples show strong green emission under UV excitation. UV irradiation (380 nm) induces down-conversion green emission at 531 nm and 552 nm and good color purity in 1 mol% Er 2 O 3 –CaMoO 4 sample which makes it a potential candidate for applications in optical devices.