Influence of sol-gel-derived ZnO:Al coating on luminescent properties of Y2O3:Eu3+ phosphor

This study deposited transparent and conductive Al-doped ZnO (AZO) thin coating on the surface of Y2O3:Eu3+ phosphor particle via a sol-gel method and analyzed the influence of soaking pretreatment, sol concentration, stabilizers, and coating temperature on the microstructure and luminescent properties of AZO-coated Y2O3:Eu3+ phosphors with the aid of SEM, TEM, cathodoluminescence (CL), and photoluminescence (PL) measurements. A water soaking pretreatment was found to effectively improve the coverage and uniformity of the AZO coating, resulting in a continuous and coherent coating. This result is attributed to the presence of adsorbed water and hydroxyl groups on the Y2O3:Eu3+ particle surface after water soaking. Monoethanolamine as a stabilizer agent and higher sol concentration led to a thicker coating on the phosphors. At 800 V or lower, the CL intensity of AZO coated Y2O3:Eu3+ phosphors is significantly greater than that of the uncoated particles and increases with coating thickness. In addition, the PL emission intensity also rises with increasing coating thickness and is even higher than bare phosphors. Further increases in coating thickness beyond the optimum value led to a decrease in PL intensity. This study thus proposes that AZO coatings with sufficient thickness and surface coverage bring about in a higher electron/UV light transport and less surface defects, resulting in an improvement in emission intensity.