Background
The width of the standard incident and receiving Soller slits of the MiniFlex is 5°, but to obtain high resolution it is possible to select a width of 2.5° (incident/receiving Soller slits) or a width of 0.5° (receiving Soller slit only).
Investigation
Fig. 1 shows a comparison of the X-ray diffraction profiles of LaB₆ powder when the Soller slit is changed, and Table 1 shows the intensity ratios, and the full width at half maximum (FWHM), which varies proportionally with resolution.
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The axial divergence or umbrella effect can be suppressed by using a Soller slit with a narrow width angle. Low angle reflections become more symmetrical, and resolution improves as a result. This is suitable for measuring samples with many peaks in the low-angle region, and samples with overlapping peaks. Fig. 2 shows the X-ray diffraction profile of mixed powder comprised of anhydrous gypsum (CaSO₄) and anatase (TiO₂). Resolution was improved by narrowing the width of the Soller slit, and the trace amount of anatase was detected due to improved of peaks.
Apparatus conditions:
MiniFlex600 (F.F tube 40 kV, 15 mA), Detector: D/teX Ultra, Scan range: 2θ = 23.5 ~ 27.5°, Step width: 0.02°
Measurement conditions:
(A) Scan speed: 60° / min., Slit conditions: DS = 1.25°, SS = 8 mm, RS = 13 mm, Soller slit: 5°, DHL = 10 mm (B) Scan speed: 15° / min., Slit conditions: DS = 0.625°, SS = 8 mm, RS = 13 mm, Soller slit: 5°, DHL = 10 mm (C) Scan speed: 0.2° / min., Slit conditions: DS = 0.1 mm, SS = 8 mm, RS = 13 mm, Incident side Soller slit: 2.5°, Receiving side Soller slit: 0.5°, DHL = 2 mm