In Situ Raman Cell for High Pressure and Temperature Studies of Metal and Complex Hydrides

Abstract

A novel cell for in situ Raman studies at hydrogen pressures up to 200 bar and at temperatures as high as 400 °C is presented. This device permits in situ monitoring of the formation and decomposition of chemical structures under high pressure via Raman scattering. The performance of the cell under extreme conditions is stable as the design of this device compensates much of the thermal expansion during heating which avoids defocusing of the laser beam. Several complex and metal hydrides were analyzed to demonstrate the advantageous use of this in situ cell. Temperature calibration was performed by monitoring the structural phase transformation and melting point of LiBH(4). The feasibility of the cell in hydrogen atmosphere was confirmed by in situ studies of the decomposition of NaAlH(4) with added TiCl(3) at different hydrogen pressures and the decomposition and rehydrogenation of MgH(2) and LiNH(2).