Air-heated solid–gas reaction setup for in situ neutron powder diffraction

The design and function of a reduction furnace, specially designed for solid–gas in situ monochromatic angular dispersive neutron powder diffraction, is presented. The functionality is demonstrated by performing a reduction experiment of CoFe₂O₄ nanoparticles at the instrument DMC at SINQ. Heating is provided by an air gun, allowing the sample to reach temperatures in the range of 300–973 K within less than 5 min. The setup is based on a single-crystal sapphire tube with one end closed. A φ scan of the tube reveals its single-crystal nature, through strong single-crystal reflections, while the remaining background is very low, uniform and flat. CoFe₂O₄ was reduced using a time resolution of 8 min and a sample volume of ∼2 cm³. By means of sequential Rietveld refinement of the in situ neutron diffraction data, a two-step reduction mechanism was discovered: CoFe₂O₄ → Co_0.33Fe_0.67O → CoFe₂. The setup offers high temperatures, fast temperature stability, large sample volumes and respectable time resolution. The setup has proven to be ideal to carry out investigations of advanced materials under realistic conditions. The ability to investigate real materials in real time under realistic conditions may be a significant advantage for scientific investigations as well as for industrial applications.