Low-cost Zn2(OH)BO3:Pb2+ phosphor for large-scale thermometric applications

A relatively low-cost blue-emitting Zn2(OH)BO3:Pb2+ crystalline powder phosphor was successfully synthesized through the hydrothermal method in a one-pot synthesis route at low temperature. The effects of dopant concentration on the structural and optical properties of Zn2–2x(OH)BO3:Pb2x (0 ≤ x ≤ 0.100) were studied. A crystal degradation and luminescence quenching occurred with dopant concentration above 1.5% mol. The synthesized phosphor had a broadband emission that peaked at 423 nm when excited with 289 nm light. While the absorption edge of the samples exhibits a redshift, the luminescence bands were not considerably changed with Pb2+ doping concentration. The optical temperature sensing capability of Zn2(OH)BO3:Pb2+ was evaluated by temperature-dependent luminescence measurements in the range of 303 – 423 K. The highest relative temperature sensitivities based on luminescence intensity and lifetime were obtained as 2.45% K−1 at 373 K and 3.04% K−1 at 403 K, respectively. A temperature gradient visualization on a surface was demonstrated using Zn2(OH)BO3:Pb2+ coating. The obtained results show that Zn2(OH)BO3:Pb2+ phosphors are a good candidate for temperature sensing on large-scale areas, covering the temperature range from 303 K to 423 K.