Influence of Gd3+ co-doping on structural property of CaMoO4:Eu nanoparticles

Abstract

A facile auto-combustion route is used for the synthesis of Gd³⁺ (2, 5, 7 and 10 at%) co-doped CaMoO₄:Eu nanoparticles. X-ray diffraction study suggests that as-prepared samples have extra impurity phases in addition to main tetragonal phase of CaMoO₄, and such extra phases decrease as the annealing temperature increases from 600 to 900 °C. The crystal structure has been analysed using Rietveld program. It has space group I4₁/a (88) and Z = 4 (number of CaMoO₄ formula units per unit cell). Average crystallite sizes of as-prepared, 600 and 900 °C annealed samples for 2 at% Gd³⁺ are found to be ∼33, 48 and 61 nm, respectively. The lattice strains of 5 at% Gd³⁺ co-doped CaMoO₄:Eu for as-prepared and 900 °C are 0.001 and 0.002, respectively. Fourier transform infrared spectroscopy gives the absorption bands at ∼815 and 427 cm⁻¹, which are related to asymmetric stretching and bending vibrations of MoO₄²⁻ tetrahedron. Particle morphology is studied using scanning and transmission electron microscopy (SEM and TEM), and aggregation of particles is found. X-ray photoelectron spectroscopy (XPS) is utilized to examine the oxidation states of metal ions/oxygen and oxygen ion vacancies in Gd³⁺ co-doped CaMoO₄:Eu. With an increase in Gd³⁺ concentration, peaks corresponding to the Gd³⁺ (2p_3/2 and 2p_5/2) binding energy could be detected.