Apparatus for rapid analysis of wide-angle X-ray diffraction patterns at high temperatures

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An apparatus has been developed which permits rapid recording of Xray diffraction patterns from inorganic powder crystals at high temperatures. The apparatus is built on a newly designed cylindrical position sensitive gas detector with an angular coverage of 120 degree of arc. The detector uses a thin metal blade in the anode and is operated in the selfquenching streamer mode. The anode radius is as large as 250mm to be compatible with most high-temperature specimen chambers. A delay line reads out the position signal from the strip cathodes to give an angular resolution of 0.05 degree of arc. The detector is mounted on a two-axis goniometer to detect a diffraction pattern from a stationary powder specimen. To suppress the broadening of reflection lines in the detected pattern, a slit system limits the angular divergence of X-rays incident on the planar specimen. The data, collected in a multi-channel analyzer memory, is read into a computer for analysis by a pattern fitting program. A test made with a standard corundom specimen demonstrates the speed and precision of the apparatus: a diffraction pattern substantially better in resolution has been obtained in a recording time of 1/80 as compared with a standard theta-two theta scanning method. The experimental pattern has been fitted well with the calculated one to give structural parameters in good agreement with the published data for this material. The usefulness of the apparatus in high-temperature works has been shown in an application, where the structure of the delta phase in bismuth oxide is refined at 784 degree Celsius.