An active Research line is the exploration of new ABO3 and A2BB’O6 perovskites containing p elements with an inert electron pair at the A positions, like Tl+, Sn2+, Pb2+, Sb3+, Bi3+, Se4+ and Te4+.
These cations create an irregular oxygen-coordination environment; therefore their stabilization in perovskites many times requires the use of high pressure conditions.
For instance, recently, TeNiO3 (with Te4+ at the A-site of the perovskite structure) was stabilized at 3.5 GPa, and the crystal and magnetic structures studied by neutron diffraction..
Concerning double perovskites, two nice examples are Bi2NiMnO6 and Bi2CoMnO6 , prepared under pressure, where the presence of a lone electron pair induces cationic shifts that favours ferroelectricity.
These materials are magneto-ferroelectrics, useful for multiple-memory devices (storage of information with both electrical and magnetic polarization) or memory elements in which a ferroelectric bit is read as a ferromagnetic bit generated by association. For instance, it is predicted a large polarization for Bi2FeCrO6 which has only been stabilized in thin film form so far: recently its preparation in bulk form has been achieved by this Group.
The role of the Pb2+ 6s lone pair in the structure of the double perovskite Pb2ScSbO6, Larregola, SA, Alonso, JA, Pedregosa, JC, Martinez-Lope, MJ, Alguero, M, De la Pena-O’shea, V, Porcher, F, Illas, F, DALTON TRANSACTIONS 28, 5453- 5459 (2009)
An Original Polymorph Sequence in the High-Temperature Evolution of the Perovskite Pb2TmSbO6, Larregola, SA, Alonso, JA, Sheptyakov, D, Alguero, M, Muñoz, A, Pomjakushin, V Pedregosa, JC, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 132, 14470- 14480 (2010)
Effect of the Pb2+ lone electron pair in the structure and properties of the double perovskites Pb2Sc(Ti0.5Te0.5)O-6 and Pb2Sc(Sc0.33Te0.66)O-6: relaxor state due to intrinsic partial disorder, Larregola, SA, Alonso, JA, Alguero, M, Jimenez, R, Suard, E, Porcher, F, Pedregosa, JC, DALTON TRANSACTIONS 39, 5159- 5165 (2010)
High-Temperature Behavior and Polymorphism in Novel Members of the Perovskite Family Pb(2)LnSbO(6) (Ln = Ho, Er, Yb, Lu), Larregola, Sebastian A.; Alonso, Jose A.; Sheptyakov, Denis; Alguero, Miguel; Munoz, Angel; Pomjakushin, Vladimir; Pedregosa, Jose C. INORGANIC CHEMISTRY 50, 5545-5557 (2011)
High-pressure synthesis and neutron diffraction investigation of the crystallographic and magnetic structure of TeNiO3 perovskite, Martinez-Lope, M. J.; Retuerto, M.; Alonso, J. A.; Sanchez-Benitez, J.; Fernandez-Diaz, M. T., DALTON TRANSACTIONS 40, 4599-4604 (2011)