Jens Kreisel

Full Speed Ahead for Perovskites

Der Kreisel, which means “the spinning top” in German, is an apt description of thirty-seven-year-old Jens Kreisel, an accomplished sportsman with a bit of a rebellious streak. After joining CNRS six years ago, this 2005 bronze medal winner¹ has pirouetted from one project to another–from non-thematic funding from ANR, the French research agency, to the European Network of Excellence, Fame.² Kreisel's interest is piqued as long as perovskite-type oxides are involved, a family of materials that he studies at the Materials and Physical Science Laboratory (LMGP).³ “With the guidance of Mike Glazer, with whom I did my postdoctoral work at Oxford University, perovskites became a subject of fascination for me,” explains Kreisel, who discovered France through his physics studies. But it was only by traveling around France for university handball matches with his team from the National Institute of Applied Sciences of Lyon that he came to fall in love with Grenoble. Nearby ski slopes could have also played a role.

After relocating to Grenoble, Kreisel continued to be spellbound by perovskites, as are many other physical chemists around the world. On the atomic scale, perovskites can be described as corner-linked octahedra (an atom B surrounded by six oxygen atoms) with atoms called A in the space between the octahedra. Almost all of the elements of the periodic table can take the place of A or B,⁴ opening the door to a limitless range of physical properties. Kreisel works, for instance, on complex perovskites known for their high piezoelectricity–i.e., electrical field by mechanical deformation and vice versa. The piezoelectricity of some perovskites is due to local heterogeneities, “comparable to the heterogeneity of raisin bread!” In such materials, atom B which is ordinarily perfectly at the center of the octahedron (in the bread dough), moves up slightly (“atomic displacement”) in the nano-scale heterogeneous parts (raisins). The problem is accessing these “raisins” and characterizing them (in terms of size, structure, and chemistry). Kreisel solves that problem by creating a major deformation of the structure under very high pressure.

“Ultimately, the choice of France has had a very positive effect on my work. As soon as I arrived at CNRS, I was given great freedom in terms of conducting my research. Two years later, I am leading my project with a generous budget. And I have used this liberty to boldly develop new experimental approaches. That doesn't exist anywhere else!”

 

Magali Sarazin