Self-organization in polycrystalline zinc sulfide prepared by self-propagating high-temperature synthesis

Bulk samples of pure and doped zinc sulfide prepared by self-propagating hi gh-temperature synthesis were studied by impedance measurements, optical mi croscopy, and Raman spectroscopy. The reaction induced by the combustion wa ve yields ZnS microcrystals aligned preferentially with their long axis nor mal to the ingot axis, which results in anisotropic electrical properties. The phonon spectrum for most of the microcrystals differs insignificantly f rom that of conventional ZnS; at the same time, the micro-Raman spectra of some microcrystals contain additional features attributable to stress-induc ed modes. The introduction of Mn has no effect on the frequency of the LO m ode, in contrast to generally accepted views.