X-RAY DIFFRACTION OF VERY SMALL SAMPLES AT EXTREME CONDITIONS OF PRESSURE AND TEMPERATURE G. Fiquet, D. Andrault, J.P. Itié, P. Richet, P. Gillet, D. Haüsermann and M. Hanfland, Laboratoire de Sciences del al Terre, ENS Lyon, 46 Allee d'Italie, 69364, Lyon Cedex 07

We present X-ray diffraction measurements carried out at the ESRF at high-pressure and high-temperature in a laser-heated diamond-anvil cell. X-ray diffraction patterns have been recorded up to 28 GPa and temperature in excess of 2500 K in an energy-dispersive mode or with a monochromatic radiation associated with imaging plates. These experiments were conducted on polycrystalline discs or polished thin sections (10-15 um thick), loaded cryogenically in dry argon acting as pressure transmitting medium, and heated by a CO₂ laser (continuous mode, 120W, TEM 00).

We used an optical set-up designed for the on-line pressure and temperature measurements, where ruby fluorescence and thermal emission of the sample are collected during X-ray diffraction acquisition and directed with optical fibers to a spectrometer placed outside the hutch. In the energy dispersive configuration, exposure times of the order of 300s were long enough to collect diffraction patterns with usable intensities up to 100 keV.

We show results obtained on a CaZr0₃ perovskite compound at high-pressure and high-temperature, which displays an orthorhombic structure at 2980K at 17.5 GPa.

Following these experiments, we present new results obtained with a monochromatic X-ray beam on the ID30-BL27 dedicated high-pressure beamline of the ESRF, realized with a 20X20 um² microfocused monochromatic X-ray spot coupled to an in-situ area detector.