A Low Angle Instrument Calibration Round Robin

The BCA Industrial Group are pleased to announce a NEW low angle calibration round robin.

The round robin is being coordinated for the Industrial Group by Dave Taylor.

The sample being used is a thin Silver Behenate film on a Polyethylene terephthalate (PET) substrate. It will be distributed as a 30mm square specimen and can be easily cut to size with scissors to fit your specimen holder. Participants in the round robin will need to measure the specimen from 1 degree to 40 degrees 2 theta for Copper Radiation or the equivalents for other wavelengths. The instrument conditions are left to participants with a recommendation of a minimum of 0.01 degree steps with a 1 second per step time interval and taking just over an hour. A template will be supplied for reporting results which will include instrument parameters and the measured data as an angles, intensity - x,y list.

Each participant will be given a unique number to protect their identity in the final report but allow them to see how their data compared with the rest. It is expected that information on angular displacement, peak intensities and line profiles will form the basis of the data evaluation. All participants can keep their test specimen as a valuable instrument calibration resource. Subject to the results of this UK Round Robin the exercise may be rolled out worldwide and the test specimen may become a certified reference material.

Why use a Silver Behenate film?
The material orients on the substrate to give multiple orders of the basal Bragg reflection. The fact that it is a reproducibly deposited film will allow direct comparison of the intensity and line profile of each instrument with no contribution from the sample or its preparation.
It is a silver carboxylate, C₂₂H₄₃O₂•Ag and crystallises as a dimer

A typical Diffraction scan from the Silver Behenate film

Crystallographic information of the bulk Silver Behenate:
Triclinic Unit Cell (Z = 2)
a = 4.71 Å, b = 4.15 Å, c = 60.30 Å
alpha = 104.5°, beta = 93.2°, gamma = 75.6°
rmeas = 1.30g/cm³, rcal = 1.35g/cm³

Sign up on line to take part now!On-line Registration form

The BCA gratefully acknowledge the support of Tom Blanton at Eastman Kodak Company, USA, for supplying the material used in this round robin exercise.