As a result of interest in the characterization of materials with large d-spacings and layer periodicities, it has become necessary to develop a low-angle diffraction material which has welldefined diffraction peaks down to very small 2θ angles. The use of silver behenate, CH3(CH2)20COO-Ag, was introduced by one of the authors (TB) at the 1991 International Centre for Diffraction Data (ICDD) Annual Meeting and was shown to have a set of well-defined (001) diffraction peaks down to 1.5° 2θ when using CuKα radiation. The silver behenate diffraction peaks were observed to be slightly asymmetric with relatively long tails at the low angle side of the peaks. The average crystallite size along the c-axis was estimated using the Scherrer equation and was found to be 900 Å.
A task group of the JCPDS-ICJDD Data Collection and Analysis Subcommittee was established with the charge of investigating the use of silver behenate as a possible low-angle calibration material for diffraction applications. Utilizing several data collection and data analysis techniques, d001 long-period spacings in the range of 58.219-58.480 Å were obtained. Using the same collected data and one data analysis refinement calculation method resulted in long-period spacing with a range of 58.303-58.425 Å. Data collected using a silicon internal standard and the same singular data analysis calculation method provided d001 values with a range of 58.363-58.381 Å.
The formation of a full-range 2θ diffraction sample was also investigated. Silver behenate and inorganic powders were mixed with an epoxy binder to form a permanent sample which provides diffraction peaks over the entire 2θ range of a powder diffractometer.