A NEW HIGH-RESOLUTION X-RAY-POWDER DIFFRACTOMETER WORKING IN THE 3-470 K RANGE FOR PHASE-TRANSITION ANALYSES

A high-resolution X-ray powder diffractometer is described with a sour ce operating from 3 to 470 K. The optical design and mechanical arrang ement of the diffractometer and the cryostat are optimized to provide easy (re)alignment procedures and high accuracy when the wavelength, t he sample or the temperature is changed. The apparatus has been tested for peak-position accuracy, angular sensitivity and resolution (using standard materials). The tests assess the overall performance of the instrument, which is comparable to (or slightly better than) the best commercial instruments, but clearly excels over them because these per formances are the same over the whole temperature range (3-470 K), all owing very accurate determination of the lattice parameters and crysta l structure.