Using XRD for the Analysis of Ilmenite Ore Samples

Ilmenite (FeTiO₃) is the essential titanium ore, accounting for up to 47% of the aggregate global production of TiO₂, a whitening pigment. The leading worldwide provider of ilmenite ore is Australia, followed by South Africa, China and Canada. The ore materializes as two alternative morphologies: heavy sand ilmenite, the most utilized morphology, and hard rock. Ilmenite constitutes solid solution series with geikielite (MgTiO₃) and pyrophanite (MnTiO₃), and can more broadly be defined as (Fe,Mg,Mn) TiO₃.

For determination of the ore grade, it is vital to apprehend both the mineralogical and chemical configuration of the sample, which are typically examined using X-ray diffraction (XRD) and X-ray fluorescence spectroscopy (XRF), respectively. XRD is most regularly undertaken utilizing Cu-Kα (1.54 Å) radiation, which conjointly stimulates the FeKα (1.94 Å) line and consequently engenders X-ray fluorescence, causing a noisy XRD pattern. A potential resolution of this issue is to utilize Co-Kα radiation (1.79 Å), or to shield the front of the detector with a PVC filter, which will absorb the low energy fluorescence.

Instruments

The Thermo Scientific™ ARL™ EQUINOX 100 X-ray diffractometer utilizes a bespoke Cu (50 W) or Co (15 W) micro-focus tube supported by mirror optics. The minimal power expended by the instrument, which negates the requirement for an external water chiller, enables it to be completely portable. This portability therefore permits convenient inter-laboratory transportation, for which specific infrastructure is no longer required.

The ARL EQUINOX 100 instrument offers extremely rapid data acquisition rates in comparison to competing diffractometers, as a result of its distinctive curved position sensitive detector (CPS). This calculates all diffraction peaks simultaneously, and in real time, and is consequently ideally suited for both reflection and transmission calculations (Figure 1).

Figure 1. ARL EQUINOX 100 X-ray diffractometer.

The Thermo Scientific™ ARL™ QUANT’X energy-dispersive XRF spectrometer employs an extremely sensitive silicon drift detector (SDD) to differentiate between the incoming radiation energy, and is thus capable of measuring every element between Na (Z = 11) and U (Z = 92). The instrument is fitted with a 50 W Rh or Ag tube, which will operate at voltages pushing 50 kV.

Transformation of spectra into elemental/oxide concentrations is attained using the Fundamental Parameters (FP) derived UniQuant standard-less package. The robust, densely packed design, coupled with the minimal requirement for external maintenance, characterize the ARL QUANT'X analyzer as a leading solution in manufacturing contexts (Figure 2).

Figure 2. ARL QUANT'X EDXRF spectrometer.

Experimental

For XRD calculations, samples of ilmenite ore deriving from Australia and China were crushed and computed in reflection geometry for 15 minutes, under Cu-Kα radiation with a PVC filter, and alongside Co-Kα radiation, to minimize the fluorescence from Fe.

Qualitative and quantitative examinations were performed utilizing MDI JADE 2010 the ICDD PDF4+ database. Prior to the EDXRF experiment, samples were crushed, screened to 200 mesh with vibromill, and pressed. The EDXRF semi-quantitative experiment results were acquired in accordance with exclusive Thermo Scientific™ UniQuant™ software.

Results

Qualitative and quantitative phase examination of Ilmenite samples offered results that are similar with both Cu-Kα radiation with PVC filter, and also Co-Kα radiation. Table 1 correlates chemical configuration from XRF and XRD (c.f., Figure 3). Regrettably, there are solid solutions for multiple compounds within the samples, and some compounds may seem formless, thus restricting the capacity of XRD measurements. Nonetheless, clear identification of the primary mineralogy of the samples remains possible.

Table 1. Chemical composition of ilmenite samples from Australia and China measured with XRF.

Figure 3. Diffraction patterns of ilmenite ore from Australia (left) and China (right) measured with Cu-Kα and PVC filter (top) and Co-Kα bottom.

The mineralogy of the samples demonstrates explicit discrepancies between the deposit sources.

The Australian ore samples comprise only anticipated minerals (valuable raw materials), while there are moderate differences between Cu-Kα and Co-Kα measurements.

Table 2. Phase composition of ilmenite from Australia

The broad trend is comparable in each case (c.f., Table 2). The Chinese ore samples (c.f. Table 3) exhibit a more extensive assortment of mineral phases, which are all linked to ilmenite deposits. There remains a divergence in the Cu-Kα and Co-Kα measurements, which is most probably a consequence of the enhanced resolution acquired with Co-Kα radiation in comparison to Cu-Kα.

Table 3. Phase composition of ilmenite from China

Conclusion

The ARL EQUINOX 100 in collaboration with the ARL QUANT’X analyzer is an extremely effective analytical solution to the comprehensive investigation of ilmenite ore samples, and the determination of their quality. The inclusion of a PVC filter to the detector of apparatus also fitted with a Cu-Kα source is an appropriate arrangement to adequately minimize Fe fluorescence. Doing so enables the determination of measurements which form the basis of qualitative and quantitative phase analysis.

Moreover, by implementing Co-Kα radiation, the collection of XRD data with enhanced resolution is possible. This data permits a more accurate quantification, particularly if phases containing closely spaced reflections or heavy peak overlap are involved. MDI JADE is a user-friendly and entirely industrialized Rietveld based software package.

XRD data is computed alongside the PDF4+ database, which allows the operator to efficiently qualify and quantify samples, even in batch operation mode. On the other hand, the UniQuant function for XRF is a highly appropriate program in the analysis of the chemical properties of any type of known or unknown samples, without necessitating prior calibration measurements.

This information has been sourced, reviewed and adapted from materials provided by Thermo Fisher Scientific - Elemental Analyzers.

For more information on this source, please visit Thermo Fisher Scientific - Elemental Analyzers.