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).
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.
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.
MiniFlex600 (F.F tube 40 kV, 15 mA), Detector: D/teX Ultra, Scan range: 2θ = 23.5 ~ 27.5°, Step width: 0.02°
(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