NaLa1-x(MoO4)2:Ho3+/Yb3+ phosphors with the correct doping concentrations of Ho3+ and Yb3+ (x = Ho3++Yb3+, Ho3+ = 0.05 and Yb3+ = 0.35, 0.40, 0.45 and 0.50) were successfully synthesized by the microwave-modified sol-gel method. Well-crystallized particles formed after heat-treatment at 900 oC for 16 h showed a fine and homogeneous morphology with particle sizes of 3-5 μm. The optical properties were examined using photoluminescence emission and Raman spectroscopy. Under excitation at 980 nm, the UC intensities of the doped samples exhibited strong yellow emissions based on the combination of strong emission bands at 545-nm and 655-nm emission bands in green and red spectral regions, respectively. The strong 545-nm emission band in the green region corresponds to the 5S2/5F4→ 5I8 transition in Ho3+ ions, while the strong emission 655-nm band in the red region appears due to the 5F5→ 5I8 transition in Ho3+ ions. Pump power dependence and Commission Internationale de L'Eclairage chromaticity of the upconversion emission intensity were evaluated in detail.

Bi co-doped ZnS:Mn,Bi yellow phosphors for white light emitting diodes were prepared by the conventional solidstate reaction method. The optical and structural properties of ZnS:Mn,Bi phosphors were investigated by x-ray diffraction, scanning electro microscopy and photoluminescence. ZnS:Mn,Bi phosphors showed XRD patterns of hexagonal structure. The photoluminescence of ZnS:Mn,Bi phosphors showed spectra extending from 480 to 700 nm, peaking at 580 nm. The photoluminescence of 580 nm in the ZnS:Mn,Bi phosphors was associated with the 4T1 → 6A1 transition of the Mn2+ ions. The highest photoluminescent intensity of the phosphors under 405 nm and 450 nm excitation was obtained at Bi concentration of 7mol%. The optimum mixing conditions with epoxy and yellow phosphor for white light emitting diodes were observed in a ratio of epoxy:yellow phosphor of 1:3.5. The CIE chromaticity of the white LED at the 1:3.5 ratio was X = 0.3454 and Y = 0.2449.

Er을 첨가한 ZnS:Mn 형광체를 1000℃에서 4시간 고상반응법으로 소결하여 제조하였다. 결정 구조 및 광 특성은 XRD, PL 그리고 SEM을 통하여 분석하였다. XRD 결과, ZnS:Mn 형광체는 hexagonal 구조가 나타났고, Er의 농도가 증가함에 따라 Er2O3 구조가 관찰되었다. ZnS:Mn 형광체의 평균입자 크기는 약 15㎛였고, Er 첨가와 함께 ZnS:Mn, Er 형광체의 입자 크기는 감소하였다. 580nm 발광 피크는 ZnS:Mn, Er 형광체에서 Mn2+ 이온의 4T1→6A1으로의 전이에 의한 것이다. Er을 0.5mol% 첨가한 형광체의 발광 세기는 Er을 첨가하지 않은 ZnS:Mn 형광체보다 높았다. ZnS:Mn, Er 형광체에서 발광 세기의 증가는 Er3+에서 Mn2+로의 에너지 전이에 의한 것으로 생각된다.