A Strategy for Rapid and Accurate (p.p.m.) Measurement of Lattice Parameters of Single Crystals by Bond’s Method
All published accounts of the use of Bond’s method for lattice parameter measurements have used step-scanning (at equal angle increments) of the diffraction peaks, followed by graphical or computer analysis of the data to locate the peak positions. It has been found that the peak angles can be determined with little loss in accuracy or precision by manually setting the crystal angle to give a counting rate (observed on a rate-meter) equal to l/2 the peak rate and defining the peak angle as the average of the angles on the two sides of the peak. Because of the asymmetry of the spectral line, defining the peak in this manner results in a shift of the peak angle from that determined by the mid-chord peak method. This shift can be compensated by determining an effective value of the wavelength based on a silicon standard. Using the method described, a lattice parameter measurement, including mounting and orienting the sample, taking the data and computing the result using a time-sharing computer terminal, can be made in less than 20 mins.
KeywordsChromium Eter Refraction Mandel
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