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Jens Kreisel
Full Speed Ahead for Perovskites
Chemistry
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
winner has pirouetted from one project to
another–from non-thematic funding
from ANR, the French research agency, to
the European Network of Excellence, Fame.1
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).2
“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.
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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,3 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!”
1. Functional Advanced
Materials and Engineering of Hybrids and
Ceramics.
2. Laboratoire des Matériaux
et du Génie Physique (CNRS / Institut
National Polytechnique de Grenoble joint
lab). LMGP is a part of Minatec, Grenoble's
center for innovation in micro- and nanotechnology.
3. The general formula
is ABO3.
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