Fig. 2

i XRD patterns of the prepared 2%Er³⁺, Yb³⁺-codoped BaYF₅ synthesized at 200 °C for 16 h with different Yb³⁺ concentrations, (a) 10%Yb³⁺ and (b) 30%Yb³⁺, the standard XRD pattern of BaYF₅ (JCPDS no.46-0039) is also given for comparison. ii UC emission spectra of the samples synthesized at 200 °C for 16 h with different Yb³⁺ concentrations. (a) 10%Yb³⁺, (b) 20%Yb³⁺, (c) 30%Yb³⁺