For the inspection of processes involving condensed matter, in situ neutron powder diffraction proves itself to be a versatile tool, giving insight into processes of technological pertinence. Only a few high-intensity powder diffractometers at intense neutron sources allow for this. D20 at Institut Laue-Langevin provides the highest available intensity in constant wavelength neutron powder diffraction. A stationary, curved linear position sensitive detector allows for in-situ diffraction studies down to a second and encourages the use of complex sample environments with inherently small sample sizes. D20 adapts to various levels of crystallographic complexity and rapidity of an observed phenomenon.
The portable electronics market, as well as non-polluting ground transportation, need portable energy storage solutions with improved characteristics. Li-ion batteries with solid electrolytes overcome issues of liquid electrolytes in battery safety and high-voltage operation. Neutron diffraction determines the Li diffusion pathway in solid-state Li-ion conductors. Development of better electrode materials in terms of gravimetric and volumetric energy density, temperature operation range and cycling stability needs understanding of lithium (de)intercalation phenomena. Operando diffraction techniques are well suited here. Electrochemical cells based on a neutron-transparent (Ti,Zr) alloy combine good electrochemical properties and the ability to collect neutron diffraction patterns with reasonable statistics and no other Bragg peaks than those of the electrode material. This allows detailed structural determination of electrode materials by Rietveld refinement during operation.
Solid-oxide fuel cells convert chemical energy into electricity at higher efficiency than conventional methods, with less pollution. The anode (fuel electrode) must not alter at high temperature (thermal stability), not form nonconductive phases at interfaces (chemical stability) and not degrade upon reduction and oxidation cycles (redox stability). The state-of-the-art “cermet” of Ni and yttria-stabilized zirconia ceramic loses performance upon usage as its porosity is reduced by Ni agglomeration and as oxidation of Ni causes redox instability. Cermet deactivates through carbon coking and sulfur poisoning, making it unsuited for hydrocarbon fuels. Single-phase mixed ionic and electronic conductors provide microstructural stability and increase the electrode fraction accessible to oxide ions. Many of those oxides have been investigated successfully in operando at high temperature under oxidizing and reducing gas flow by neutron diffraction, following the crystal chemistry of oxide ions during the process.
Classical in situ work (thermo-diffractometry) has been done on the photovoltaic materials, MaPbI3 and derivates, and neutron diffraction turned out to be a perfect tool to screen the crystal chemistry of light organic atoms beside the heavy metal atoms over a wide range of temperatures.
Hydrogen is an attractive energy carrier for renewable energy sources due to its high energy density. Solid-state hydrogen storage provides higher storage capacities than compressed or liquefied hydrogen. Complex metal hydrides have high hydrogen storage capacities but suffer from poor kinetic and thermodynamic properties. Tuning the thermodynamics for dehydrogenation, to reduce the temperature at which hydrogen is evolved is achieved through the addition of a second phase, which will lead to the formation of a more stable product upon decomposition and thereby reducing the enthalpy for dehydrogenation. Neutron powder diffraction screens the crystal chemistry of the different phases in situ.
Finally, the work on the structure and the formation and decomposition of gas hydrates and related ice phases will be presented, as well as the prospects of work at very high pressures up to 25 GPa at low temperatures down to 1.6 K.