Compositional nanodomain formation in hybrid formate perovskites.

We report the synthesis and structural characterisation of three mixed-metal formate perovskite families [C(NH2)3]CuxM1-x(HCOO)3 (M = Mn, Zn, Mg). Using a combination of infrared spectroscopy, non-negative matrix factorization, and reverse Monte Carlo refinement, we show that the Mn- and Zn-containing compounds support compositional nanodomains resembling the polar nanoregions of conventional relaxor ferroelectrics. The M = Mg family exhibits a miscibility gap that we suggest reflects the limiting behaviour of nanodomain formation.