Photo- and cathodoluminescence of hydrothermally synthesized Y(sub 3)Al(sub 5)O(sub 12):Tb and NaY(WO(sub 4))(sub 2):Tb

摘要

Cathodoluminescent (CL) phosphors with improved low-voltage characteristics are needed for use in emissive flat panel displays. Conventional high-temperature methods for phosphor synthesis yield large polycrystalline grains that must be pulverized prior to screen deposition. Grinding has been implicated in reducing phosphor efficiency by causing surface contamination and defects. Hydrothermal synthesis has been used to improve the quality of ceramic powders by producing fine, well-formed crystallites without grinding. Two green-emitting phosphors, Y(sub 3)Al(sub 5)O(sub 12):Tb (YAG:Tb) and NaY(WO(sub 4))(sub 2):Tb, were used to test the effects of hydrothermal. synthesis on grain size and morphology, and on low-voltage CL properties. YAG:Th prepared hydrothermally consisted of submicron crystallites with a typical garnet habit. The CL efficiency of hydrothermally synthesized YAG:Tb (3 lm/W at 800 V) was comparable to that of equivalent YAG:Tb compositions prepared via high-temperature solid state reaction. In comparison, CL intensities of Gd(sub 3)Ga(sub 5)O(sub l2):Tb were slightly better (3.5 lm/W at 800 V), while those of NaY(WO(sub 4))(sub 2):Tb were approximately 1/100th that of YAG:Tb. Both CL and photoluminescence data show that the difference in the cathodoluminescence of YAG and NaY(WO(sub 4))(sub 2) can be understood in terms of differences in the mechanism of activation.