Abstract

The understanding of ABO3 perovskite remains one of the most challenging topics at the interface between solid state chemistry and solid state physics. The use of pressure for the investigation of perovskites has remained relatively rare, also due to the experimental difficulties, which have now been overcome for a number of years. As a consequence, we observe an evolution of high-pressure studies from a “niche” activity, reserved to some experts, to an increasingly important activity. In my presentation I will first recall the perovskite structure and the relation between the different structural distortions and physical properties. I will then discuss the pioneer rules of Samara [1] which have guided for years the interpretation of the effect of high-pressure on perovskites. In the second part of the talk I will focus on our own observations by high-pressure Raman scattering and synchrotron scattering experiments of three classes of perovskites : (i) Ferroelastics, such as LaAlO3, SrTiO3 & CaTiO3 [2-5], (ii) Classic ferroelectrics like PbTiO3 [6-7] and, in some more detail, (iii) The multiferroic BiFeO3 [8-9]. These different examples will allow discussing in more general terms the effect of high-pressure on octahedra tilting, cation displacement and the competition between these two instabilities

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