Designing new n = 2 Sillen-Aurivillius phases by lattice-matched substitutions in the halide and [Bi2O2]2+ layer
Australian Institute of Physics
The chemical and structural flexibility of the perovskite structure, which makes it so ubiquitous in nature and useful in a range of technological applications, extends to layered variants such as Ruddlesden-Popper, Dion- Jacobson and Aurivillius phases. Multi-layered variants such as the Sillen-Aurivillius phases are related to Aurivillius phases by the insertion of an additional halide layer between every second [Bi2O2]2+ layer. Sillen-Aurivillius phases exist in various combinations of n number of perovskite layers and m halide layers. We have synthesised a new n = 2, m = 1 Sillen-Aurivillius compound Bi3Sr2Nb2O11Br based on Bi3Pb2Nb2O11Cl by simultaneously replacing Pb2+ with Sr2+ and Cl- with Br-. Rietveld refinements against X-ray and neutron powder diffraction data revealed a significant relative compression in the stacking axis, in contrary to the belief of inserting a significantly larger halide layer in the new compound. We could not stabilise other combinations such as Bi3Sr2Nb2O11Cl and Bi3Pb2Nb2O11Br due to inter-layer mismatch. Sr2+ doping reduces the impact of the stereochemically active 6s2 lone pair found on Bi3+/Pb2+ site, resulting in a contraction of the stacking axis by 1.22 % and an expansion of the a-b plane by 0.25 %, improving inter-layer compatibility with Br-. XANES analysis shows that the ferroelectric distortion of the B-site cation is less apparent in Bi3Sr2Nb2O11Br compared to Bi3Pb2Nb2O11Cl. Variable-temperature neutron diffraction data show no evidence for a ferroelectric distortion.
Alkaline earth metals, Elements, Halogen compounds, Materials, Mechanical properties, Metals, Spectroscopy, Layers, Perovskites
Liu, S., Blanchard, P. E. R., Kennedy, B. J., Ling, C. D., & Avdeev, M. (2014). Designing new n = 2 Sillen-Aurivillius phases by lattice-matched substitutions in the halide and [Bi2O2]2+ layer. Poster presented to the 38th Annual Condensed Matter and Materials Meeting 2014, Waiheke Island Resort, Waiheke, Auckland, New Zealand, 4th February - 7th February, 2014. Retrieved from: https://physics.org.au/wp-content/uploads/cmm/2014/Wagga2014proceedings.pdf