Structural polytypism in B-site deficient azetidinium-based pnictogen halide hexagonal perovskites (dataset)

Azetidinium (Az+) based antimony and bismuth organic-inorganic hybrid halide B-site deficient perovskite analogues Az3B2X9 (B3+ = Sb, Bi; X– = Cl, Br, I) were systematically studied. All Az3B2X9 stoichiometries adopt hexagonal close packed perovskite structures with the 6H (hcc)2 stacking sequence differing only in the positions of the ordered B-site vacancies. In Az3Sb2Cl9 and Az3Sb2Br9 ordering of B-site vacancies in a single face sharing octahedral layer leads to the formation of an unusual 2D layered polar structure with P63mc space group. Variable temperature single crystal and powder XRD, DSC, DTA and dielectric spectroscopy showed several successive phase transitions at low temperature associated with distortions of the octahedral framework and order/disorder of the Az+ cation. In contrast, in Az3Sb2I9, Az3Bi2Br9 and Az3Bi2I9 the preferred arrangement of vacancies at alternating corner sharing octahedral sites generates a 0D dimer structure. This work highlights the flexibility for structural variations based on particular configurations of vacancy ordering in B-site deficient halide perovskites.