TY - JOUR
T1 - Crystal Structure Evolution and Notable Thermal Expansion in Hybrid Perovskites Formamidinium Tin Iodide and Formamidinium Lead Bromide
AU - Schueller, Emily C.
AU - Laurita, Geneva
AU - Fabini, Douglas H.
AU - Stoumpos, Constantinos C.
AU - Kanatzidis, Mercouri G.
AU - Seshadri, Ram
N1 - Funding Information:
This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Award DE-SC-0012541. We thank Catherine Oertel for useful comments. Use of the shared experimental facilities of the Materials Research Science and Engineering Center at UCSB (MRSEC NSF DMR 1720256) is gratefully acknowledged. The UCSB MRSEC is a member of the NSF-supported Materials Research Facilities Network (www.mrfn.org). D.H.F. thanks the National Science Foundation Graduate Research Fellowship Program for support under Grant DGE 1144085. Use of the Advanced Photon Source (Beamline 11-BM) at Argonne National Laboratory was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
PY - 2018/1/16
Y1 - 2018/1/16
N2 - The temperature-dependent structure evolution of the hybrid halide perovskite compounds, formamidinium tin iodide (FASnI3, FA+ = CH[NH2]2+) and formamidinium lead bromide (FAPbBr3), has been monitored using high-resolution synchrotron X-ray powder diffraction between 300 and 100 K. The data are consistent with a transition from cubic Pm3m (No. 221) to tetragonal P4/mbm (No. 127) for both materials upon cooling; this occurs for FAPbBr3 between 275 and 250 K, and for FASnI3 between 250 and 225 K. Upon further cooling, between 150 and 125 K, both materials undergo a transition to an orthorhombic Pnma (No. 62) structure. The transitions are confirmed by calorimetry and dielectric measurements. In the tetragonal regime, the coefficients of volumetric thermal expansion of FASnI3 and FAPbBr3 are among the highest recorded for any extended inorganic crystalline solid, reaching 219 ppm K-1 for FASnI3 at 225 K. Atomic displacement parameters of all atoms for both materials suggest dynamic motion is occurring in the inorganic sublattice due to the flexibility of the inorganic network and dynamic lone pair stereochemical activity on the B-site. Unusual pseudocubic behavior is displayed in the tetragonal phase of the FAPbBr3, similar to that previously observed in FAPbI3.
AB - The temperature-dependent structure evolution of the hybrid halide perovskite compounds, formamidinium tin iodide (FASnI3, FA+ = CH[NH2]2+) and formamidinium lead bromide (FAPbBr3), has been monitored using high-resolution synchrotron X-ray powder diffraction between 300 and 100 K. The data are consistent with a transition from cubic Pm3m (No. 221) to tetragonal P4/mbm (No. 127) for both materials upon cooling; this occurs for FAPbBr3 between 275 and 250 K, and for FASnI3 between 250 and 225 K. Upon further cooling, between 150 and 125 K, both materials undergo a transition to an orthorhombic Pnma (No. 62) structure. The transitions are confirmed by calorimetry and dielectric measurements. In the tetragonal regime, the coefficients of volumetric thermal expansion of FASnI3 and FAPbBr3 are among the highest recorded for any extended inorganic crystalline solid, reaching 219 ppm K-1 for FASnI3 at 225 K. Atomic displacement parameters of all atoms for both materials suggest dynamic motion is occurring in the inorganic sublattice due to the flexibility of the inorganic network and dynamic lone pair stereochemical activity on the B-site. Unusual pseudocubic behavior is displayed in the tetragonal phase of the FAPbBr3, similar to that previously observed in FAPbI3.
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U2 - 10.1021/acs.inorgchem.7b02576
DO - 10.1021/acs.inorgchem.7b02576
M3 - Article
C2 - 29278493
AN - SCOPUS:85047633647
VL - 57
SP - 695
EP - 701
JO - Inorganic Chemistry
JF - Inorganic Chemistry
SN - 0020-1669
IS - 2
ER -