Microwave-Modified Sol-Gel Process for Microcystalline KY(WO₄)₂: Ho³⁺/Yb³⁺ Phosphors and their Upconversion Photoluminescence Properties

Abstract

KY 1-x (WO 4) 2 :Ho 3+ /Yb 3+ yellow phosphors with doping concentrations of Ho 3+ and Yb 3+ (x = Ho 3+ + Yb 3+ , Ho 3+ = 0.05, 0.1, 0.2 and Yb 3+ = 0.2, 0.45) were successfully prepared using the microwave-modified sol-gel method; their upconversion (UC) photoluminescence properties were investigated in detail. Well-crystallized particles, formed after heat-treatment at 900°C for 16 h, showed a fine and homogeneous morphology with particle sizes of 2-5 µm. Under excitation at 980 nm, the UC KY 0.7 (WO 4) 2 :Ho 0.1 Yb 0.2 and KY 0.5 (WO 4) 2 Ho 0.05 Yb 0.45 particles exhibited excellent yellow emissions based on a strong 545-nm emission band in the green region and a very strong 655-nm emission band in the red region. Pump power dependence and Commission Internationale de L'Eclairage chromaticity of the UC emission intensity were evaluated. The spectroscopic properties were examined comparatively using Raman spectroscopy.

Up- and Down-Conversion Luminescence of LuNbO4:Yb3+, Er3+ Phosphors

“…Yb 3+ ions are typically used as sensitizers owing to their strong absorption of 980 nm, while Er 3+ , Tm 3+ , and Ho 3+ ions are co-doped as activators, resulting in various UC spectra. 9,10) In the case of the Yb 3+ -Er 3+ system, under infrared (IR) radiation (980 nm), the energy absorbed by the sensitizers (Yb 3+ ions) is transferred to the activators (Er 3+ ions), leading to a multistep excitation of the Er 3+ ions: ground-state absorption (GSA) and excited-state absorption (ESA). 11) For UC phosphors codoped with the Yb 3+ and Er 3+ ions, the UC emission spectra typically exhibit multiple-emission peaks in the green and red regions; the emission ratio of green to red closely depends on the host materials.…”