Development of oxyfluoroborate glass ceramics doped with Er³⁺ and Yb³⁺

The preparation of oxyfluoroborate glasses and glass–ceramics doped with Yb³⁺ and Er³⁺ with improved luminescent properties is reported. Glasses with compositions (100 − x − y) (MO·2B₂O₃) + xPbF₂ + y(YbF₃:ErF₃) (% in mol), where M is Sr, Ba, Ca, x = 10–40% and y = 0, 1 or 5% were prepared by the melt/quenching technique. Glass crystallization was studied using thermal analysis and X-ray diffraction techniques. Optical absorption and infrared up-conversion were studied on both glasses and glass–ceramics. The incorporation of a fluoride compound into the borate glass resulted to depend on the ionic radius of the glass modifier: as it increases, glasses become more stable against crystallization. On the other hand, alkali–fluoride compounds such as BaF₂ and SrF₂ can be crystallized from these systems by selecting an appropriate proportion between their components. Furthermore, the up-conversion response can be tuned by changing the glass modifiers (Sr, Ba and Ca) of the borate matrix, which also influence the type of fluoride crystallized compound. The strontium glass–ceramics have the highest luminescence response due to the crystallization of SrF₂ compound in the system SrO–B₂O₃–PbF₂. Meanwhile, the lowest luminescence signal was obtained for samples in the system BaO–B₂O₃–PbF₂ where the Pb_1.33Ba_2.66B₁₁FO₂₀ phase crystallizes. With this strategy, new materials with improved luminescence properties that can be used as up converters, were obtained.