A new X-ray powder diffractometer working in the 87-1000 K range for phase-transition analyses

An X-ray powder diffractometer, operating in the 87-1000 K temperature range, is described. The experimental procedure and data analysis allow the measurement of small lattice distortions and very small parameter variations with good accuracy. The experiment setup is devoted to the detection of phase transitions, to the determination of thermal expansion curves and to the study of kinetic chemical reactions in situ. The apparatus has been tested for angular sensitivity and resolution. The tests assess the overall performance of the instrument over the entire range of temperature. The cell parameter of the standard material cubic Na₂Ca₃Al₂F₁₄ in the 90-600 K range is given as example. In a study of the thermal expansion of the cell parameter of cubic AgI in the 303-553 K range, a phase transition, of first-order character, is found between 398 and 453 K.