The local and average structure of Ba(Ti, Ce)O3 perovskite solid solution: effect of cerium concentration and particle size

The amazing properties of ferroelectric perovskite BaTiO3 (BT) and its solid solutions make them indispensable for many technological applications (e.g. multilayer capacitors). Unfortunately, the so-called `size effect' limits their use. Indeed, under a certain critical particle size, these materials show a suppression of the spontaneous polarization and thus of the ferroelectric properties. In pure nanometric BaTiO3, this is related to a certain local structural disorder. However, only a few studies have explored BT solid solutions, where the doping effect, coupled to the reduced particle size, can play an important role. Therefore, in this work, the structure of BaCexTi1-xO3 (x = 0.02-0.20) was explored by traditional Rietveld method and Pair Distribution Function. Samples present a particle size from 80-160nm to 400-1000nm depending on increasing x. The carbox approach was applied, investigating the evolution of the local structure, its modifications and the structural coherent correlation length, as a function of cerium amount. Results demonstrate a cooperative effect of composition and reduced size in the ferroelectricity loss. The two, in fact, contribute to intensify the local structural disorder, decreasing the structural coherent correlation length. The local structural disorder is thus confirmed to be a relevant factor in the ferroelectric properties degradation.