Nano perovskite and the "size effect": the case of BaTiO3 doped by CeIV

BaTiO3 perovskite and its solid solutions, as BaTi1-xMIVxO3, are nowadays the most used ferroelectric. These materials are friend-environmental ferroelectrics, being lead-free, and show excellent properties. In this light, they are very useful in very different fields, but unfortunately their characteristics limit their applications in nano technology. Indeed, in these perovskites, the reduced size induces the so called "size effect" which consists in a disappearance of the ferroelectricity under a critical grain size [1]. This degradation of the material properties is then really problematic considering the present tendency in device miniaturization. In order to better understand this phenomenon, many studies have been performed. In pure BaTiO3 the "size effect" and the polarization reduction seem to be linked to the increasing local structural disordered nature of the nano powders as reported by Petkov et al. [2], Page et al. [3], Yoneda et al. [4]. However similar conclusions are not be previously proposed for doped BaTiO3, then the case of nano BaTi1-xCexO3 perovskite is here presented. The purpose is to explore the relation between the reduced size and the structure, as a function of cerium amount. Rietveld method and Pair Distribution Function were applied to give a complete picture of the average and local structure. Data collection was performed at ID22, European Synchrotron Radiation Facility (ESRF), Grenoble, France [5]. In this case study the use of the synchrotron radiation and an appropriate instrumentation is essential. In one hand high resolution data were necessary to recognize phase transitions, observable despite the peak broadness caused by the nano size of the material. On the other hand, in order to obtain suitable Pair Distribution Functions, data has to be collected at very high Qmax. The high quality of the data allowed to obtain good results on both average and local structure. Performed analyses show how the reduced size and the doping amount act at the structural level and how this is linked to the material properties. [1] N. Nuraje, K. Su, Nanoscale 2013, 5(19), 8752-8780. [2] V. Petkov, V. Buscaglia, M.T. Buscaglia, Z. Zhao, Y. Ren, Physical Review B 2008, 78(5). [3] K. Page, T. Proffen, M. Niederberger, R. Seshadri, Chemistry Of Materials 2010, 22(15), 4386-4391. [4] Y. Yoneda, S. Kohara, K. Kato, Japanese Journal Of Applied Physics 2013, 52(9, 2, SI). [5] www.esrf.eu