X-ray powder diffraction analysis of silver behenate, a possible low-angle diffraction standard

Silver behenate, a possible low-angle diffraction standard, was characterized using the powder diffraction technique. Diffraction patterns obtained with 1.54 Å synchrotron and Cu Kα radiations showed thirteen regularly spaced (00l) peaks in the range 1.5–20.0°2θ. With the National Institute of Standards and Technology's standard reference material silicon as an internal standard, the long spacing of silver behenate was accurately determined from the profile-fitted synchrotron diffraction peaks, with d₀₀₁ = 58.380 (3) Å. This result was in agreement with that obtained from the Cu Kα pattern. The profile widths of the silver behenate peaks were found to be consistently larger than those of the silicon peaks, indicating significant line broadening for silver behenate. The average crystallite size along the long-spacing direction of silver behenate was estimated using the Scherrer equation, giving D_avg = 900 (50) Å. Because silver behenate has a large number of well defined diffraction peaks distributed evenly in the 1.5–20.0°2θ range, it is suitable for use as an angle-calibration standard for low-angle diffraction. However, care must be taken if silver behenate is to be used as a peak-profile calibration standard because of line broadening.