SYMMETRY PECULIARITIES OF THE INTRACRYSTALLINE FIELDS LAYERED SEMICONDUCTOR CRYSTALS (PbI$_2$)$_{(1-x)}$ (BiI$_3$)$_{(x)}$

Abstract

In this work the results of the investigation of the $^{127}$I NQR spectra at 77K for mixed layered semiconductor crystals (PbI$_2$)$_{(1-x)}$ (BiI$_3$)$_{(x)}$ in a wide range of value (0 \textless x \textless 0.50) are presented. It is shown that in the range 0.05 \textless x \textless 0.20 of admixture PbI$_2$ the observed behavior of parameters of the $^{127}$I NQR spectra testify about entrance of admixture atoms PbI$_2$ into the crystal layers. It is shown, that at 0.05 \textlessÊ x \textless 0.20 clusters from groups of atoms PbI$_2$ insular type can be formed, which lay within the limits of the layers of crystal (PbI$_2$)$_{(1-x)}$ (BiI$_3$)$_{(x)}$. Upon further increasing of the containing of admixture PbI$_2$ in crystal BiI$_3$ the "new" $^{127}$I NQR line is appearing. The observed at x $_\textasciitilde$ 0.20 the new line in spectrum $^{127}$I NQR can testify that the mixed crystal (PbI$_2$)$_{(1-x)}$ (BiI$_3$)$_{(x)}$ undergoes structural phase transition. It is concluded that at x\textgreater 0.20 a new crystal presents a solid mixture glassy crystal of substitution type in which of PbI$_2$ atoms are fully or partially are ordering and lay between crystal .