Formation of the HgI2 crystalline phase in the bulk and on the surface of nanocrystalline matrices

This paper reports on the results of investigations into the phase composition of HgI2 microcrystals formed in the bulk and on the surface of different nanocrystalline matrices: pressed, finely dispersed (with a specific surface of more than 210 m2/g) aluminum oxide powders; porous borosilicate glasses with pore radii ranging from 2 to 20 nm; and Al2O3-HgI2 and SiO2-HgI2 nanocrystalline composites. The results of spectroscopic analysis (diffuse reflection, absorption, and luminescence spectroscopy) are complemented by the data of atomic-force microscopy (AFM) and x-ray diffraction. The experimental results indicate that nonequilibrium modifications, namely, the high-temperature yellow phase and the orange phase metastable in bulk crystals at all temperatures, can be stabilized in HgI2 nanoparticles at room temperature.