Micro-, Nanostructural Properties of the $\text{MgAl}_{2}\mathrm{O}_{3}$ Ceramics Studied by Combined Methods

Phase composition, microstructure, porosity in the
$\text{MgAl}_{2}\mathrm{O}_{4}$
ceramics sintered at 1200 °C for 2 h for sensor applications in electronics were studied using combined methods (X-ray diffraction, scanning electron microscope, Hg-porosimetry, positron annihilation lifetime spectroscopy). It is shown that the obtained ceramics contains three phases. It has a branched structure of grains, intergranular boundaries and pores with trimodal pore size distribution. It is shown that the presence of water in ceramics is accompanied by more intense capture of positrons on defects near the grain boundaries with additional phases. The presence of water in ceramics leads to the fragmentation of the free volume of nanopores and the additional decomposition of ortho-positronium atoms in the adsorbed water.