Fabrication Of Titania Coatings On ZnS-Type Phosphors Using The Titanium Diethanolamine As The Precursor In The Aqueous Solution

Recently, field emission displays (FED) have been developed as the next-generation flat panel displays to replace cathode-ray tubes (CRTs). However, due to the low acceleration voltages and high current densities in a FED, most conventional CRT phosphors are not appropriate for field emitter arrays, especially the ZnS-type phosphors. Surface reactions occur on the ZnS surface during prolonged electron bombardment. The ageing performance is believed to be associated with the surface recombination of phosphors. In this study, TiO₂ coatings are expected to inhibit fast degradation of ZnS phosphors applied in FEDs due to their chemical, thermal stability and wide band-gap.(1) Use TiCl₄ as the precursor in an aqueous solution, and keep the reaction in an ice bathing.(2) Use Ti(OBu)₄ as the precursor in an alcohol solution. The influence of the water volume, solvent volume, pH value, the inhibitor (HAC) and the adding order of the materials were studied separately.(3) Used titanium diethanolamine complex as the precursor in an alcohol solution. The influence of the titanium diethanolamine complex solution concentration, reaction temperature, reaction time, the inhibitor (CTAB) were studied separately to ensure the optimal coating condition; The titanium diethanolamine complexes were synthesized with the different molar ratio of DEA to Ti(OBu)₄, and the chealating complexes and the possible reaction were induced; The inner mechanism of the sol-gel and coating process were explored; The uncoated and titania coated ZnS phosphors were investigated by varies methods.In our study, the TiO₂ nanocoatings on ZnS phosphors were successfully obtained by the sol-gel process in an aqueous solution using the titanium diethanolamine complex as the precursor. The nanocoatings synthesized by this technique were uniform and continuous with a thickness of about 10-15 nm, and the photoluminescent spectra showed that no other luminescent center was introduced. The titania coatings with an appropriate thickness were expected to prevent the degradation of ZnS phosphors in FEDs.