Institute of Materials Science, University of Tsukuba* Graduate School of Pure and Applied Sciences, University of Tsukuba, Japan** Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Japan***
○Miwako Takahashi* Yuji Fujii** Takurou Kawasaki** Kataoka Kunimitsu** Masashi Watanabe*** Ken-ichi Ohshima*
The structure and phase transition in the one-dimensional semiconductor C5H10NH2PbI3 has been investigated by using x-ray and neutron single crystal diffraction methods. C5H10NH2PbI3 has a lead-based inorganic-organic perovskites structure consisting of semiconducting parts which are composed of one-dimensional chains of face-sharing lead-iodide octahedra and barrier parts composed of C5H10NH2+ molecules. It has been shown by Raman scattering that the structure undergoes successive phase transitions below the room temperature which involves rotational/orientational ordering of the organic C5H10NH2+ parts. However, its precise structure has not been determined even for the room temperature. The aim of the present study is to clarify the structural change and its effects on the electronic state in the phase transition of C5H10NH2PbI3. By combining the data obtained by x-ray and neutron single crystal diffraction, its structural model at room temperature including positional information for Hydrogen and Nitrogen atoms is proposed. The temperature- and pressure- induced phase transitions in C5H10NH2PbI3 have also been investigated. The temperature variation of neutron diffraction patterns shows drastic changes below 250K, indicating a symmetrical change of the structure takes place at around 250K. The lattice constant for b-axis shows large contraction of 5.84% at this temperature together with the expansion of a- and c- axis of 0.51 and 1.54 %, respectively. These changes indicate that the phase transition induced by rotational and orientational ordering of C5H10NH2+ molecules, as predicted by Raman scattering, occurs around 250K. The structural model below 250K is now under consideration and will be presented.