Using Laboratory Diffractometer for Qualitative PDF Analysis of Pigment Yellow 213

Table of Contents

Introduction
Setup and Results

Introduction

To study the effect of the wavelength and the detector noise using a laboratory powder diffractometer for determination of PDF and the maximum evaluable Q-value, a 1 mm glass capillary has been filled with Pigment Yellow 213 (1) (PY213) and adjusted on a goniometer head of a Stoe Stadi P powder diffractometer in Debye-Scherrer geometry at the Stoe & Cie application laboratory.

Setup and Results

Pigment Yellow 213, C23H21O9N5.

Figure 1. Pigment Yellow 213, C23H21O9N5.

Data has been collected from set-ups with Cu-, Mo- and Ag-anode sealed tubes and the respective Ge(111)-monochromator for pure Kα1- radiation as well as a Dectris MYTHEN 1K detector equipped with a wavelength optimized chip (320, 450 or 1000 μm thickness), a linear and an IP-PSD.

Data evaluation has been performed by the Department of Inorganic Chemistry, Goethe University Frankfurt, using PDFgetX2 (2).

Setup and Results

Figure 2. Background and powder pattern of PY213 measured with Cu- and lin. PSD, Moand IP PSD as well as Ag-radiation and MYTHEN 1K (large to small).

A Fourier transformation of the diffraction data F(Q) with Q=4∂(sinθ/λ) provides the observed PDF G(r), which, in turn, yields the probability to determine a pair of atoms in the distance r. It is possible to calculate the maximum theoretical Q value directly from 2θ (max) of the goniometer.

F(Q) for PY213 with Ag-radiation.

Figure 3. F(Q) for PY213 with Ag-radiation.

For the Stadi P, the Q(theo max) value could be 20 Å-1 for Ag-radiation, but the observed Q(max) value is very low. G(r) yields a Q(obs max) of approximately 7 Å-1, 10 Å-1 and 13 Å-1 for Cu-, Mo-, and Ag-radiation, respectively. For ESRF Synchrotron data with λ = 0.40 Å, Q(obs max) is found to be 14 Å-1 (3).

G(r) for PY213 measured with Cu-, Mo- and Ag-radiation

Figure 4. G(r) for PY213 measured with Cu-, Mo- and Ag-radiation (left to right).

As expected, the highest Q (obs max) is yielded by the shortest wavelength.

Stoe Stadi P with MYTHEN 1K.

Figure 5. Stoe Stadi P with MYTHEN 1K.

The low noise and excellent resolution of the Dectris MYTHEN 1K make it the detector of choice. The pure Ag Kα1-radiation from the Ge(111) monochromator allows the Stoe Stadi P powder diffractometer to score as well in XRD as in PDF calculation.

References

1. Schmidt, M.U. et al., Acta Cryst. (2009). B65, 189-199

2. Qiu, X., Thompson, J.W. & Billinge, S.J.L. J. Appl. Cryst. (2004). 37, 678.

3. Presentation of Martin U. Schmidt, EPDIC, Warszawa, Sept. 2008

STOE

This information has been sourced, reviewed and adapted from materials provided by STOE.

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