Synthesis, crystal structure and phase transition in a perovskite type (CH3NH3)2M(X)2(Y)2(M=Sn; X=SCN; Y=Cl)

The exploration of ferroelectric hybrid materials is highly appealing due to their great technological significance.
In line with this, we herein report the development of a new ferroelectric relaxor: (CH3NH3)2Sn(SCN)2Cl2 was
synthesized and studied by single-crystal X-ray diffraction, powder XRD, Differential scanning calorimetry
(DSC), IR spectroscopy and dielectric measurements. The phase purity was confirmed by Rietveld refinement of
the X-ray powder diffraction pattern. It crystallizes, at room temperature, in the orthorhombic system with the
Pnm21 space group. The crystal structure is formed of discrete ionic entities (CH3NH3)+ and (Sn(SCN)2Cl2)2-. The
methylammonium cations are bonded to these chains by hydrogen-bonding contacts. DSC measurement shows
that this compound exhibits a diffuse ferro–paraelectric phase transition around 355 K. Dielectric study exhibits
a relaxor behavior characterized by the transition temperature shifts toward higher temperature with the rise of
frequency. This behavior was validated by the modified Curie–Weiss law. The diffuseness parameter was the γ is
approach to 1.96 at 2000 KHz