The Waterloo Institute for Nanotechnology (WIN) presents a seminar by Professor Harald Hillebrecht, Institute for Inorganic Chemistry, University of Freiburg, Germany.
Inorganic Energy Materials − Contributions from Solid State Chemistry
Contributions
from
solid
state
chemistry
to
inorganic
energy
materials
may
originate
from
two
different
directions.
One
aspect
is
the
synthesis
and
characterization
of
new
compounds
for
possible
applications.
Another
point
is
the
development
of
synthetic
strategies
to
obtain
well-known
materials
with
enhanced
properties
or
in
a
more
efficient
way.
One
field
for
inorganic
energy
materials
are
thermoelectrics.
Bi1-xSbx
(x
≈
0.15)
is
the
best
thermoelectric
material
at
low
temperatures
around
200
K.
Nanoparticles
were
obtained
by
a
simple
and
upscalable
solution-based
process.
ZT-values
are
comparable
to
material
made
by
mechanical
alloying.
For
high-temperature
applications
(>1000
K)
the
solid
solution
Si1-xGex
is
obtained
by
SPS.
Homogenous
polycrystalline
samples
can
be
pressed
into
pellets
which
were
used
as
feed
rod
for
the
single
crystal
growth
by
a
floating
zone
technique
in
a
mirror
oven.
SPS
was
also
used
for
a
one-step
synthesis
of
BiCuSeO,
which
is
also
a
promising
material
for
medium
temperatures.
Fe2-xCoxAlB2
was
established
as
a
new
magnetocaloric
material
where
the
co-content
shifts
Tc
between
300
K
(x
=
0)
and
200
K
(x
=
0.3).
Similar
related
ternary
borides
like
Fe3Al2B2,
Ru9Al3B8
and
Ru9Al5B8-x.
MAX-phases,
i.e.
ternary
carbides
or
nitrides
of
the
series
(MX)nMA
(M
=
Ti,
V,
Nb,
..;
A
=
Al,
Si,
Ga,
..;
X
=
C,
N;
n
=
1,
2,
3)
are
investigated
as
machinable
ceramics,
and
very
recently
as
material
for
batteries,
catalysts,
or
capacitors.
We
have
analyzed
solid
solutions
of
different
representatives
of
M
and
A
based
on
single
crystal
investigations.
Similar
properties
can
be
expected
for
analogous
ternary
borides
(MB2)nMA.
Organic-inorganic
hybride
perovskites
like
MAPbI3
(MA
=
CH3NH3)
are
excellent
dyes
for
the
dye-sensitized
solar
cell.
Within
a
few
years
the
efficiency
was
increased
to
over
20%.
The
combination
of
two
different
organic
cations
like
guanidinium
(Gu),
formamidinium
(Fo)
or
thioformamidinium
(Tu)
modifies
the
dimensionality
of
the
framework
of
edge-sharing
PbI6
octahedra
to
layered
structures
with
varying
thickness
and
topology.
This
has
an
impact
on
optical
properties
and
chemical
stabilities.
The
classification
of
the
crystal
structures
is
similar
to
oxidic
Ruddlesden-Popper
phases.
Further
fragmentation
to
different
1D
structures
is
possible,
but
the
resulting
large
band
gap
prohibits
an
application.