Synthesis of Microwave Sol–Gel Derived NaCaLa ( WO 4 ) 3 :Ho 3+ /Yb 3+ Phosphors and Their Spectroscopic Properties

Ho 3+ /Yb 3+ co‐doped NaCaLa 1 − x ( WO 4 ) 3 ternary tungstates with the proper concentrations of doping for Ho 3+ and Yb 3+ ( x  = Ho 3+ + Yb 3+ , Ho 3+  = 0, 0.05, 0.1, and 0.2, and Yb 3+  = 0, 0.2, and 0.45) were precisely synthesized using the sol–gel method assisted by the microwave technique; their upconverted spectroscopic properties were studied in detail. The particles provided well‐crystallized morphology with a homogeneous and fine morphology, showing the grain sizes of 2–5 µm. After the low excitation at 980 nm, the NaCaLa 0 .7 ( WO 4 ) 3 :Ho 0.1 /Yb 0.2 and NaCaLa 0 .5 ( WO 4 ) 3 :Ho 0.05 /Yb 0.45 ternary tungstates provided strong upconverted yellow emissions, which are based on a strong green emission band of 545 nm and a strong red emission band of 655 nm. The optimal Yb 3+ :Ho 3+ ratio was obtained to be 9:1, as indicated by the composition‐dependent quenching effect of Ho 3+ ions. The Raman spectra for the doped ternary tungstates showed the presence of strong peaks at higher frequencies, which were superimposed by strong Ho 3+ luminescence lines. The dependence of pump power and Commission Internationale de L'Eclairage ( CIE ) chromaticity of the upconverted emission intensity was investigated in detail.