Abstract This work reports dielectric properties of methylammonium lead iodide as a function of frequency, temperature, and dc bias electric field studied in terms of grain and grain boundary contributions.… Click to show full abstract
Abstract This work reports dielectric properties of methylammonium lead iodide as a function of frequency, temperature, and dc bias electric field studied in terms of grain and grain boundary contributions. These results were analyzed from the perspective of a relaxor-like ferroelectric nature. The temperature dependence of dielectric permittivity at different frequencies showed a wide dispersion in the vicinity of the tetragonal-cubic phase transition, suggesting a relaxor ferroelectric feature after excluding artifacts as Maxwell-Wagner effects and dc contributions. The results from plots of the Vogel-Fulcher and the modified Curie-Weiss laws indicate the existence of a freezing temperature of the dipoles responsible for the relaxor character of the material ( T f ∼ 270 K) and a diffuse phase transition at high temperatures ( γ ∼ 1.52-1.74). Measurements on heating and cooling protocols under a dc bias electric field suggest field-induced polarized domains like relaxor ferroelectric. The observed signatures of transitions between non-ergodic and ergodic relaxors to ferroelectric states were attributed to polar nano regions dynamics, suggesting a critical electric field around 0.03 kV cm−1.
               
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