The successive phase transitions of the polymorphs of CsSnI3 were studied by means of the powder X-ray diffraction and their crystal structures were analyzed at three different temperatures by the Rietveld method.
A series of solid solutions, CH3NH3Sn1−xPbxBr3 (x=0–1), having cubic perovskite structures was obtained by solid-state reactions. The 119Sn Mössbauer spectra for x<0.4, however, indicated that the tin environment was considerably distorted from a regular octahedron at 110 K. On the other hand, a single Lorentzian spectrum having a large isomer shift was observed for x>0.7, suggesting the presence of a regular SnBr6 octahedra in the perovskite CH3NH3PbBr3 matrix. The high electrical conductivity of the perovskite CsSnBr3 drastically decreased upon the replacement of the cation by CH3NH3 and the central metal by Pb. This behavior suggests that both the infinite linear chain (–Br–Sn(Pb)–Br–) and its bond length have significant importance regarding electrical conductivity.
Successive phase transitions were observed for CsSnBr3 and CH3NH3SnBr3 by means of 81Br NQR and DTA. These compounds are isomorphous with each other and have typical cubic perovskite structures at room temperature. However, with decreasing temperature both compounds showed successive phase transitions and complex 81Br NQR spectra at 77 K. In the case of CH3NH3SnBr3, both 81Br NQR and 119Sn Mössbauer spectra changed markedly with decreasing temperature from those at room temperature. These findings suggested a large distortion of the SnBr6 octahedron from the regular one and were interpreted on the basis of the three-center-four-electron bond model. In relation to these structural changes, a broad-line 1H NMR experiment on CH3NH3SnBr3 was also observed in order to determine the effect of the dynamic properties of the cation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.