Annealing temperature and oxygen-vacancy-dependent variation of lattice strain, band gap and luminescence properties of CeO₂nanoparticles

Abstract

CeO2 nanoparticles are annealed in vacuum at 200°C and in air at 200°C, 600°C and 1000°C, respectively. Vacuum-annealed CeO2 contains high concentration of oxygen vacancies and exhibits very high lattice strain, whereas the corresponding values decrease on air annealing. Oxygen-deficient CeO2 has redshift in band gap with high Urbach energy. The magnitude of this energy decreases as CeO2 is annealed in air at 600°C. At 1000°C, thermal disorder increases the Urbach energy. Photoluminescence property of the samples depends on the presence of radiative and non-radiative oxygen vacancy centres. Vacuum-annealed ceria have large numbers of non-radiative oxygen vacancies that act as emission quencher. CeO2 annealed at 600°C contains requisite amount of oxygen vacancies to show better luminescence property.