A method for crystallographic texture investigations using standard x-ray equipment
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A method for crystallographic texture investigations using standard x-ray equipment Mark D. Vaudin NIST, Ceramics Division, Gaithersburg, Maryland 20899
Martin W. Rupich, Martha Jowett, and G. N. Riley, Jr. American Superconductor Corp., Two Technology Drive, Westborough, Massachusetts 01581
John F. Bingert Los Alamos National Lab, Materials Technology, Los Alamos, New Mexico 87545 (Received 25 November 1997; accepted 18 March 1998)
A fast and accurate method has been developed for measuring crystalline texture in homogeneous materials. The method uses a conventional powder x-ray diffractometer capable of u scans. Two scans are recorded from the sample: first, a high resolution u-2u scan is obtained of a Bragg peak whose diffracting planes are normal to the preferred orientation direction; second, a u scan is obtained using this peak. The u scan contains the required texture information, but the intensities must be corrected for defocusing and absorption to obtain the texture profile. The u-2u scan of the Bragg peak is used to make the defocusing correction, and first principles calculations are used to correct for absorption. The theory behind these corrections is presented here. The validity of the technique has been verified by making measurements on untextured alumina. Data obtained from Bi2 Sr2 Ca2 Cu3 O10 superconducting tape specimens with this technique are compared with texture data obtained with a four-circle diffractometer.
I. INTRODUCTION
It is frequently desirable, in both applied and basic research, to be able to perform rapid, accurate texture measurements. For example, during the development of a product where crystallographic texture plays an important role in the performance of the product, it is necessary to assess the effects of different manufacturing processes on texture and to correlate the observed texture with measured properties. To date, accurate texture measurements have required specialized equipment not available in most laboratories. However, many laboratories have access to conventional powder x-ray diffractometers, and this paper describes a technique that uses such a diffractometer and is both fast and accurate. The work reported in this paper is concerned with texture that is axisymmetric about a single sample axis, also known as fiber texture. The texture axis (fiber axis) is a specimen direction, such as the normal to a flat specimen or the axis of a rod-shaped specimen. Extensions to this work will consider more complex textures. To describe the axisymmetric texture of a crystalline phase in a specimen, we specify the preferred crystallographic direction, i.e., the crystal direction preferentially aligned with the texture axis. In order to quantify a fiber texture, diffraction techniques are typically used to measure the volume fraction of the specimen whose preferred crystallographic direction is at a certain angle to the fiber axis. This angle corresponds to the angle of specimen 2910
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