YAG : R3+ (R = Ce, Dy, Yb) nanophosphor-based luminescent fibre-optic sensors for temperature measurements in the range 20–500 °C

We report the development of a group of luminescent fibre-optic temperature sensors that use Ce³⁺-, Dy³⁺-, and Yb³⁺-doped yttrium aluminium garnet (YAG) nanophosphors as thermosensitive materials. The nanophosphors have been prepared in the form of powders with a crystallite size from 19 to 27 nm by a polymer – salt method and exhibit bright luminescence at 550 (YAG : Ce³⁺), 400, 480 (YAG : Dy³⁺), and 1030 nm (YAG : Yb³⁺). The sensor design includes a silica capillary, partially filled with a nanophosphor, and two large-aperture multimode optical fibres located in the capillary, which deliver excitation light and receive and transmit the photoluminescence signal. The photoluminescence signal amplitude of all the sensors decreases exponentially with increasing temperature, pointing to characteristic thermal quenching of photoluminescence and adequate operation of the devices up to 500 °C. The highest temperature sensitivity among the fibre-optic sensors is offered by the YAG : Ce³⁺ nanophosphor-based devices.