Analysis of the low-temperature dielectric relaxation in $$\hbox {CH}₃\hbox {NH}₃\hbox {PbI}₃$$ CH 3 NH 3 PbI 3 partially substituted with Sn and Ba

In this work, we partially replaced Pb with non-toxic elements to form hybrid perovskites (hbox {CH}₃hbox {NH}₃ hbox {Pb}_0.9hbox {M}_0.1hbox {I}₃), where (hbox {M} = hbox {Sn}²⁺) and (hbox {Ba}²⁺) and studied their dielectric properties. According to room-temperature Rietveld analysis, all compositions with 10 % substitution were tetragonal with a space group (I4/hbox {mcm}). A notable dielectric relaxation was detected at (Tsim 60)–(100hbox { K}), far below the orthorhombic-to-tetragonal phase transition at (Tsim 155hbox { K}). To clarify the conflicting literature reports, the dielectric relaxation was fitted to both Arrhenius and Vogel–Fulcher models and showed no indication of the finite (i.e. non-zero) dipolar freezing temperature. It is concluded, therefore, that the low-T dielectric dispersion is a signature of the Debye-type thermally activated re-orientation of the non-interacting electric dipoles with an activation energy of (E_mathrm{{a}} sim 123-171hbox { meV}).