TY  - JOUR
A1  - Franz, Alexandra
A1  - Többens, Daniel M.
A1  - Steckhan, Julia
A1  - Schorr, Susan
T1  - Determination of the miscibility gap in the solid solutions series of methylammonium lead iodide/chloride
JF  - Acta Crystallographica Section B:
Structural Science, Crystal Engineering and Materials
N2  - Perovskites are widely known for their enormous possibility of elemental substitution, which leads to a large variety of physical properties. Hybrid perovskites such as CH3NH3PbI3 (MAPbI(3)) and CH3NH3PbCl3 (MAPbCl(3)) are perovskites with an A([XII])B([VI)X(-)([II)(])structure, where A is an organic molecule, B is a lead(II) cation and X is a halide anion of iodine or chlorine. Whereas MAPbCl(3) crystallizes in the cubic space group Pm (3) over barm, MAPbI(3) is in the tetragonal space group I4/mcm. The substitution of I by Cl leads to an increased tolerance against humidity but is challenging or even impossible due to their large difference in ionic radii. Here, the influence of an increasing Cl content in the reaction solution on the miscibility of the solid solution members is examined systematically. Powders were synthesized by two different routes depending on the I:Cl ratio. High-resolution synchrotron X-ray data are used to establish values for the limits of the miscibility gap which are 3.1 (1.1) mol% MAPbCl(3) in MAPI(3) and 1.0 (1) mol% MAPbI(3) in MAPCl. The establishment of relations between average pseudo-cubic lattice parameters for both phases allows a determination of the degree of substitution from the observed lattice parameters.
KW  - powder diffraction
KW  - hybrid perovskites
KW  - miscibility gap
KW  - MAPbX3
Y1  - 2018
U6  - https://doi.org/10.1107/S2052520618010764
SN  - 2052-5206
VL  - 74
SP  - 445
EP  - 449
PB  - International Union of Crystallography
CY  - Chester
ER  - 
TY  - JOUR
A1  - Lehmann, Frederike
A1  - Franz, Alexandra
A1  - Toebbens, Daniel M.
A1  - Levcenco, Sergej
A1  - Unold, Thomas
A1  - Taubert, Andreas
A1  - Schorr, Susan
T1  - The phase diagram of a mixed halide (Br, I) hybrid perovskite obtained by synchrotron X-ray diffraction
JF  - RSC Advances
N2  - By using synchrotron X-ray powder diffraction, the temperature dependent phase diagram of the hybrid perovskite tri-halide compounds, methyl ammonium lead iodide (MAPbI3, MA+ = CH3NH3+) and methyl ammonium lead bromide (MAPbBr3), as well as of their solid solutions, has been established. The existence of a large miscibility gap between 0.29 ≤ x ≤ 0.92 (±0.02) for the MAPb(I1−xBrx)3 solid solution has been proven. A systematic study of the lattice parameters for the solid solution series at room temperature revealed distinct deviations from Vegard's law. Furthermore, temperature dependent measurements showed that a strong temperature dependency of lattice parameters from the composition is present for iodine rich compositions. In contrast, the bromine rich compositions show an unusually low dependency of the phase transition temperature from the degree of substitution.
Y1  - 2019
U6  - https://doi.org/10.1039/c8ra09398a
SN  - 2046-2069
VL  - 9
IS  - 20
SP  - 11151
EP  - 11159
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Franz, Alexandra
A1  - Többens, Daniel M.
A1  - Lehmann, Frederike
A1  - Kärgell, Martin
A1  - Schorr, Susan
T1  - The influence of deuteration on the crystal structure of hybrid halide perovskites: a temperature-dependent neutron diffraction study of FAPbBr(3)
JF  - Acta crystallographica; Section B, Structural science, crystal engineering and materials
N2  - This paper discusses the full structural solution of the hybrid perovskite formamidinium lead tribromide (FAPbBr(3)) and its temperature-dependent phase transitions in the range from 3 K to 300 K using neutron powder diffraction and synchrotron X-ray diffraction. Special emphasis is put on the influence of deuteration on formamidinium, its position in the unit cell and disordering in comparison to fully hydrogenated FAPbBr(3). The temperature-dependent measurements show that deuteration critically influences the crystal structures, i.e. results in partially-ordered temperature-dependent structural modifications in which two symmetry-independent molecule positions with additional dislocation of the molecular centre atom and molecular angle inclinations are present.
KW  - hybrid perovskite
KW  - FAPbBr(3)
KW  - deuteration
KW  - neutron powder diffraction
KW  - crystal structure
Y1  - 2020
U6  - https://doi.org/10.1107/S2052520620002620
SN  - 2052-5206
VL  - 76
IS  - 2
SP  - 267
EP  - 274
PB  - Wiley-Blackwell
CY  - Oxford [u.a.]
ER  -