Mössbauer and electronic-reflectance spectroscopic studies and resistivity measurements on the systems CsPb1–xSnxBr3, CsPb1–xSnxBr2Cl, MxCs1–xSnBr3, and MxCs1–xSnBr2Cl (M = Na, K, Rb, and NH4)

Abstract

A series of coloured compounds of general formula CsPb_1–xSn_xX₃(X₃= Br₃ or Br₂Cl) has been prepared. X-Ray and Mössbauer data show that the compounds have highly symmetrical tin–lead environments. Their electronic resistivity and optical-reflectance spectra are interpretable in terms of the partial filling of electronic bands produced by the interaction of orbitals of the bromine atoms. As x increases the band population increases, consistent with the lower ionisation energies of the tin 5s electrons compared to those of the lead 6s electrons. Replacement of Cs⁺ by Na⁺, K⁺, Rb⁺, or [NH₄]⁺ shows that these singly charged ions have no effect on band formation. Replacement of Br₃ by Br₂Cl raises the energy of the band due to the inclusion of the higher-energy chlorine orbitals.