Doping Effect of Bi~(3+) on the Properties of YAG:Ce~(3+),Mn~(2+) Phosphor Ceramics for Warm WLEDs

A series of Bi³⁺-doped YAG:Ce³⁺, Mn²⁺ ceramics was synthesized successfully by gel-casting method and structurally characterized by XRD and SEM. The doping effect and related mechanism of Bi³⁺ upon the luminescent property were studied. It can be assigned to the energy transfer of multipolar interaction from Bi³⁺ to Ce³⁺, leading to the improvement of emission intensity about 58% for 0.0001 Bi³⁺ and 0.05 Mn²⁺ doping. In addition, the emission is significantly red-shifted with the peak at 590 nm for the Y2.9939 Ce0.006 Bi0.0001 Al4.96 Mn0.02 Si0.02 O12 ceramic specimen with in-line transmittance 81.6% at 1100 nm. The LED module assembled from Y2.9939 Ce0.006 Bi0.0001 Al4.96 Mn0.02 Si0.02 O12 ceramic owns correlated color temperature(CCT) of 3960 K and luminous efficiency(LE) of 92 lm/W, implying that doping Bi³⁺ shows a good sensitization effect in the YAG:Ce³⁺, Mn²⁺ ceramic system and further serving as an attracting phosphor candidates for warm WLEDs applications.     

Synthesis of High-purity Fe2AlB2 and the Effect as Sintering Additive for ZrB2

Fe₂AlB₂ powder material was prepared by the direct reaction of iron,aluminum and boron powders in a tubular furnace.The effects of different Al contents,temperature and raw material pretreatment on the purity of product were studied.The mixed powder with the stoichiometric ratio of 1.5Al/2Fe/2B was processed by CIP (Cold Isostatic Pressing),and then calcined at 1150℃ for 120 min.The product containing a small amount of impurities is treated with alkaline solution to obtain high-purity Fe₂Al B₂ powder.Zr B₂-Fe₂Al B₂ composite ceramic was successfully prepared at 1250℃ by hot pressing sintering.The density,hardness and fracture toughness were 96.2%,22±0.3 GPa and 5.78±0.5 MPa·m^1/2,respectively.