INVESTIGATION OF SOLID-STATE REACTIONS AND SOLID-SOLID PHASE-TRANSFORMATIONS WITH TIME-RESOLVED AND TEMPERATURE-RESOLVED X-RAY-POWDER DIFFRACTOMETRY

An X-ray powder diffractometer has been equipped with a heatable sample holder which allows highly defined heating up to 250-degrees-C. A good temperature control permits isothermal as well as non-isothermal runs. The applicability of time- and temperature-resolved X-ray powder diffractometry (TXRD) as a thermoanalytical method is demonstrated. Solid state reactions and solid-solid phase transformations were investigated. As examples the phase transformation of phenanthrene and the dehydration of caffeine hydrate are presented. It is possible to extract the activation parameters for a solid state reaction from a single non-isothermal run with a constant heating rate. The principles of the quantitative kinetic evaluation of time- and temperature-resolved X-ray powder diffraction data are outlined.