The visable light absorption and color reversible mechanism of Co doping cubic zirconia single crystals after X-ray irradiation

In order to obtain an efficient high-energy radiation detection materials, the reversible discoloration of Co doping cubic zirconia (c-ZrO₂) with irradiation was studied. The optical absorption, the elemental content, the valence states of Co and Zr, and the type of O elements of c-ZrO₂ were analyzed by ultraviolet–visible absorption spectroscopy, X-ray diffractometry, X-ray photoelectron spectroscopy, electron paramagnetic resonance spectroscopy and thermoluminescence spectroscopy to demonstrate the influence of internal defects on the color reversed of c-ZrO₂. The experimental results showed the X-ray irradiation and the subsequent LED lighting/heat treatment on blue c-ZrO₂ resulted in a significant reversible discoloration process, in which the color caused Co²⁺ in ZrO₂ replaced Zr⁴⁺ thus oxygen vacancy occurred. After X-ray irradiation, the color change is related to the increase of oxygen vacancy, and the subsequent LED lighting/ heat treatment filled the oxygen vacancy, thus enabling a color reversible process in c-ZrO₂.