As part of WP1 – Traceable, quantitative thermal imaging from -100 °C to 500 °C, SMU have carried out preliminary measurements to characterise the emissivity of phosphor-based coatings.

The measurements were performed on three phosphor material samples deposited on aluminium substrates, using the virtual source method to determine their emissivity. The initial measurements were conducted at a surface temperature of 200 °C.

During the experiments, each sample was mounted on a heating element and brought to the required temperature using a resistance heater positioned behind the sample. Once the sample had stabilised at the target temperature, a detector and the other components of the measurement setup were positioned in the line of sight of the sample. The resulting signal was then processed to determine the emissivity of the phosphor coating. The schematic and a photograph of the experimental setup are shown below.

These measurements are an important step towards improving the characterisation of phosphor materials for high-temperature and traceable temperature measurement applications. Understanding their emissivity behaviour is essential for evaluating and developing reliable optical temperature measurement techniques.

The next stage of the work will extend the measurements to higher temperatures, up to 250 °C (surface temperature), with the measurements repeated for all three phosphor samples. The results will contribute to the ongoing ThermoSI activities aimed at advancing accurate and SI-traceable temperature measurement technologies for industrial applications.