A reactor for in situ, time-resolved neutron diffraction studies of microwave-induced rapid solid-state chemical reactions.

Abstract

Utilizing direct microwave- (MW)-induced heating in solid-state synthesis yields the clear benefits of greatly reduced reaction times and lower energy requirements as compared with conventional methods. Here, we describe a bespoke single-mode cavity (SMC) MW reactor designed to operate within a neutron beamline that allowed powder diffraction data to be collected from materials in situ as they were heated using MWs. The unique set-up was used to investigate the rapid solid-state synthesis of the binary metal chalcogenide thermoelectric (TE) materials Bi₂Se₃, Bi₂Te₃, Sb₂Se₃ and Sb₂Te₃. The resultant time-resolved diffraction data from each synthesis were time-sliced post-reaction into segments covering periods of tens of seconds, enabling the reaction progression to be visualized as colourmap plots. This technique enabled the accurate tracking of polycrystalline structure formation and a quantitative analysis of phase fractions during the accelerated heating and subsequent cooling stages of each reaction. Our investigations have also revealed some of the present limitations of rapid in situ neutron diffraction techniques and how these might be remedied.This article is part of the discussion meeting issue 'Microwave science in sustainability'.