Study on the structure and optical properties of phosphor Ca3La3(BO3)5:Dy3+ for potential application in temperature sensing

Abstract A series of single phase calcium lanthanum borates Ca3La3(BO3)5:Dy3+ (CLBD) phosphors were synthesized via conventional solid-state reaction. The introduction of Dy3+ with a preferred location on La3+ over Ca2+ site in CLB is owing to the different ionic radii and charge valent and confirmed by XRD, Rietveld refinements and photoluminescence analysis. Under ultraviolet (UV) excitation, tunable colors of high-brightness emissions were realized by controlling the Dy3+ doping concentrations. The CLBD demonstrated potential application as non-contact and self-calibration thermometer. Two different effective strategies for temperature sensing were investigated, namely, fluorescent intensity ratio (FIR) and emission decays. The FIR method was employed the fluorescence ratio of 4I15/2 → 6H15/2/4F9/2 → 6H15/2 due to the Boltzmann-like distribution of the two exited energy levels with temperature while the decay lifetimes were fitted and compared by adopting three different theoretical models: multiphonon relaxation (MR), charge transfer (CT) and transformed CT (TCT, which further consideration the relationship between CT energy and temperature). Altogether, the CLBD phosphors show promising potentials for temperature sensing.