Tetragonal-Cubic Phase Transition and Low-Field Dielectric Properties of CHNHPbI Crystals.

The frequency and temperature dependence of dielectric properties of CHNHPbI (MAPI) crystals have been studied and analyzed in connection with temperature-dependent structural studies. The obtained results bring arguments for the existence of ferroelectricity and aim to complete the current knowledge on the thermally activated conduction mechanisms, in dark equilibrium and in the presence of a small external a.c.