Radiophotoluminescence properties of Bi-doped NaCaBO₃

Bi-doped NaCaBO3 exhibits radiophotoluminescence (RPL) properties, where the Bi2+ centre is formed through X-ray irradiation. As a result of RPL, a broad emission band appears around 800 nm in the photoluminescence (PL) spectrum, attributed to X-ray irradiation. The intensity of the PL signal is proportional to the irradiation dose, making it useful for measuring accumulated radiation dose. The sensitivity depends on the doping concentration of Bi, and the optimal concentration to maximize sensitivity is approximately 0.005%. With a laboratory-constructed reader system, the optimal sample enables measurement of X-ray dose as low as 25 mGy. Following irradiation, the Bi2+ signal slightly increases by about 13%, but it is significantly reduced to around 7% of the initial value after heat treatment at 500 degrees C for 100 s. The formation and annihilation of the Bi2+ centre can be reproduced multiple times. Therefore, RPL of Bi-doped NaCaBO3 is attractive for radiation dosimetry applications.