Effects of molten-salt processing parameters on the structural and optical properties of preformed La2Zr2O7:Eu3+ nanoparticles

Abstract

Molten-salt method has been used to synthesize various functional materials, but it has not been employed to adjust the structure, particle size, and properties of preformed particles. To fill the knowledge gap, in this study, we use a molten-salt medium to reprocess preformed La2Zr2O7:5%Eu3+ nanoparticles which were already formed by a molten-salt synthesis (MSS) method. The molten-salt processing is conducted under various conditions in terms of processing time, temperature, and medium. Specifically, within the studied molten-salt processing time (0 h–24 h) at 800°C, 3 h was found to offer the best optical output. In terms of the investigated molten-salt processing temperature (650 °C–1100 °C) for 3 h, 800 °C was identified as the most desirable annealing temperature. Regarding the explored molten-salt processing media (nitrate vs. chloride) at 3 h and 800 °C, better luminescence results were obtained for nanoparticles processed in chloride. Under each processing parameter, the change of optical properties is explained based on the balance among the crystalline size, crystal structure, crystallinity, defect, and agglomeration characteristics of the molten salt processed La2Zr2O7:5%Eu3+ particles. We expect this study will excite other scientists to further explore molten-salt processing as an effective post-synthesis method to fine-tune the structure, particle size, and properties of preformed particles to meet the demand of functional materials.