Synthesis of YVO4:Eu3+ phosphors and the effect of nano-sized SiO2 on the optical properties

Abstract

In this work, bulk sized YVO4:Eu3+ phosphor was synthesized via simple solid state method in air atmosphere at 1100 °C, which has a variety of applications in the fields of lighting and solar cells. All these applications are possible due to the proper designation of particle size, morphology and defects control of surface through the experimental parameters. Referring to the literatures, synthesis of the YVO4:Eu3+ phosphors in the air atmosphere, results in the formation of many defects and then the optical properties are suppressed. For improvement of luminescence properties, the surface of YVO4:Eu3+ phosphor was coated by a thin layer of SiO2 through sol-gel (with a source of TEOS) and then obtained morphology and photoluminescence properties were investigated in details. It was found that silica coating yields an increase in luminescence intensity of the YVO4:Eu3+ phosphors due to the reduction of reflection of excitation light and the maximum amounts of emission intensity was obtained with 1 wt% silica coating when the thickness of silica on the surface is in the range of 20-50 nm. Another effective mechanism for luminescence improvement is the decrease of surface defects by coating the surface of phosphor. The ESR analyses approved that with coating of a layer of silica on the surface of YVO4:Eu3+ phosphor, the amounts of oxygen vacancy defects reduced remarkably. Furthermore, the coating of YVO4:Eu3+ phosphors by silica enhanced the chemical and thermal stability too. Also, in another procedure and to study the effect of SiO2 core on YVO4:Eu3+ phosphors, the YVO4:Eu3+@SiO2 phosphors were synthesized through sol-gel process too. It was found that after 5 times coating of YVO4:Eu3+ on SiO2 core, the emission intensity is significantly comparable to that of pure YVO4:Eu3+ phosphors. In addition, although the coating of YVO4:Eu3+@SiO2 phosphors with silica resulted in decrease of luminescence properties but the thermal quenching and chemical stability were enhanced.