Perovskites in low dimensional multi-layer structure types
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Date
2014-08
Journal Title
Journal ISSN
Volume Title
Publisher
International Union of Crystallography
Abstract
This study introduces examples of structure property relationships within the multi-layered Sillen-Aurivillius family (shown in Figure) and aims to investigate the effect of chemical doping and lattice matching effects. The first example involves doping 1/3 of the n = 3 ferroelectric perovskite layers with magnetic transition metal cations in Bi 5 PbTi 3 O 1 4 Cl [1] with charge balancing by removing Pb 2 + for Bi 3 + . A statistical 1:2 distribution of M 3 + and Ti 4 + across all three perovskite layers was found in Bi 6 Ti 2 MO 1 4 Cl, M = Cr 3 + , Mn 3 + , Fe 3 + , resulting in highly strained structures (enhancing the ferroelectricity compared to Bi 5 PbTi 3 O 1 4 Cl) and pronounced spin-glass behavior below T i r r (0) = 4.46 K. Ferroelectric transitions were observed at high temperature for each of the new compounds. Ferroelectric properties were also measured on Bi 6 Ti 2 FeO 1 4 Cl using piezoresponse force microscopy showing hysteretic phase behavior. A new n = 2 Sillen-Aurivillius compound Bi 3 Sr 2 Nb 2 O 1 1 Br, based on Bi 3 Pb 2 Nb 2 O 1 1 Cl [2], was synthesized by simultaneously replacing Pb 2 + with Sr 2 + and Cl - with Br - . Inter-layer mismatch prevented the formation of Bi 3 Sr 2 Nb 2 O 1 1 Cl and Bi 3 Pb 2 Nb 2 O 1 1 Br. Sr 2 + doping reduces the impact of the stereochemically active 6s 2 lone pair found on Pb 2 + and Bi 3 + , resulting in a stacking contraction in the lattice parameters by 1.22 % and an expansion of the a-b plane by 0.25 %, improving inter-layer compatibility with Br - . X-ray Absorption Near Edge Structure spectra analysis shows that the ferroelectric distortion of the B-site cation is less apparent in Bi 3 Sr 2 Nb 2 O 1 1 Br compared to Bi 3 Pb 2 Nb 2 O 1 1 Cl. Variable-temperature neutron diffraction data show no evidence for a ferroelectric distortion. © International Union of Crystallography
Description
Keywords
Perovskite, Spin glass state, Ferroelectric materials, Transition elements, Cations, Crystal doping, Neutron diffraction
Citation
Liu, S., Miiller, W., Liu, Y., Blanchard, P., Avdeev, M., Kennedy, B., & Ling, C. (2014). Perovskites in low dimensional multi-layer structure types. Presentation to the XXIII IUCr Congress Montreal, Canada, 5-12 August. In Acta Crystallographica Section A: Foundations and Advances, 70(a1), C1363-C1363. doi.org/10.1107/S2053273314086367