A handy guide to complex cluster formation in the crystalline model of two-dimensional layered perovskite halide salt

摘要

The paper presents significantly salient issue in the field of two dimensional halide-based perovskites with diammonium cations on the example of one of their representatives, ie. compound of chemical formula (NH3)(2)(CH2)(3)CdBr4, as one of the important contemporary targets. We have focused our attention on the mechanism of complex cluster formation revealed by dielectric spectroscopy measurements. Dielectric modulus representation obtained for the investigated sample was interpreted within the stochastic scenario of the correlated-dusters scheme. The eye-catching feature of analyzed compound is relaxation response governed by the contribution of two relaxation processes in the high-temperature structural modifications, L a Ima2 (phase II) and P2(1)/m (phase III), which showed the generalized Mittag-Leffler two-power-law relaxation pattern, while the room temperature phase Prima (phase I) is portrayed only by the Cole-Cole relaxation law. Also demonstrated that dielectrically active are all the phase transformations in the analyzed compound. The odd number of carbon atoms in the alkylammonium chains as well as hydrogen and ionic bonding scheme with trans effect affect on the unusual electric behavior and point to complex duster formation in the analyzed alkylene-diammonium complex. Optical measurements indicate that the investigated material is an 'inversely' improper ferroelastic, support the existence of structural rearrangement/disorder, and also confirm the subsistence of trans effect manifesting itself as the anti-phase domain walls, not visible in the polarization microscopy.