Figure 26.

(a) Crystal structure of pure CHA₂PbBr₄ compound in the ferroelectric (FE) and paraelectric (PE) phases. Cation disorder is present in the PE phase. (b) Temperature dependence of the (b) SHG response and (c) real part ε′ of the complex dielectric permittivity (1 MHz) of the mixed CHA₂Pb(Br_1–xI_x)₄ system (x = 0, 0.11, and 0.18). (d) Ferroelectric hysteresis loops of the same compounds obtained at room temperature. Reprinted (adapted) with permission from ref (397). Copyright 2016 Wiley-VCH.