Screen printed thick films of NiO and LaFeO₃ as gamma radiation sensors

Thick films of nickel oxide (NiO) and perovskite type LaFeO₃ were investigated for γ-radiation dosimetry purposes. Samples were fabricated using the thick film screen printing technique. These films were exposed to a ⁶⁰Co γ-radiation source with a dose rate of 6Gy/min. The effects of γ-radiation on both the optical and the electrical properties of NiO and LaFeO₃ films were studied. Absorption spectra for the specimens were recorded and the values of the optical band gap for as-printed and γ-irradiated films were calculated. It was found that the optical band gap values decreased with the increase in radiation dose. To study changes in the electrical properties of the materials, two types of specimens having sandwich metal-semiconductor-metal structure were made with layers of NiO and LaFeO₃, respectively. Commercial DuPont 4929 silver paste was used to manufacture electrical contacts. It was observed that radiation induced changes in the electrical properties for both types of thick films, e.g. values of current decreased with an increase in radiation dose. It was found that annealing restored both the electrical and the optical properties of the samples.