Investigation of changes in positronium trapping in pores under the water influence in nanostructured MgO-Al2O3 ceramics

Abstract

It is known that nanostructured MgO-Al2O3 ceramics are one of the best materials for humidity sensors. The functionality of such ceramics is dependent on microstructure of grains, grain boundaries and pores. These elements significantly affect on their nanostructurization. In addition, electrical properties of ceramics depend on the sorption processes in these materials. In this work we used positron annihilation lifetime (PAL) spectroscopy to investigation of changes in PAL parameters in nanopores MgO-Al2O3 ceramics sintered at 1100 °C at different stage of water-immersion and drying. The PAL investigation were performed using ORTEC spectrometer (22Na source) in the ceramic samples dried in vacuum at 120 °C for 4 hours as well as after 1, 2, 3 and 7 days immersion in water vapor. The four-component fitting procedure with positron lifetimes tau1, tau2, tau3 and tau4 and intensities I1, I2, I3 and I4 was used for analysis of PAL spectra.