This article analyzes lithium carbonate (Li₂CO₃) extracted from salars using X-Ray diffraction (XRD). Salars, which are salt flats or salt pans, are sources of lithium, where Li₂CO₃ or LiOH is derived from brines or saltwater through a series of evaporation steps.
Lithium carbonate finds wide application in batteries, ceramics, glass, and other industries, emphasizing the significance of its purity and crystallinity for ensuring the quality of the final products.
XRD, a non-destructive technique, provides valuable structural insights into crystalline materials. Its common uses include phase identification, quantification, and determining crystalline structures within a sample.
The XRD analysis results offer valuable insights into the quality and purity of Li₂CO₃ extracted from salars, crucial for its utilization across diverse industries.
Figure 1. ARL X’TRA Companion diffraction system. Image Credit: Thermo Fisher Scientific - Elemental Analyzers and Phase Analyzers
Instrument
The Thermo Scientific™ ARL™ X’TRA Companion (Figure 1) is the instrument for this study. It is a user-friendly benchtop XRD system for process control and advanced applications. The system employs a θ/θ goniometer (160 mm radius) in Bragg-Brentano geometry and a 600 W X-Ray source (Cu or Co).
Controlling radial and axial collimation of the X-Ray beam is achieved through divergence and Soller slits, while a variable beam knife reduces air scattering. An optional integrated water chiller is available.
The ARL X’TRA Companion boasts a state-of-the-art solid-state pixel detector (55 x 55 µm pitch) for rapid data collection. It features one-click Rietveld quantification capabilities and automated result transmission to a LIMS.
Experimental
In the experimental phase, two powdered samples of Li₂CO₃ from salars underwent reflection geometry measurements using the ARL X’TRA Companion with Cu Kα radiation (Ni filter). Each sample was measured for 10 minutes. Phase quantification utilized Profex1 with the BGMN algorithm, employing a fundamental parameters approach.
Figure 2. Rietveld fit of Li₂CO₃ sample A (10 minutes). Image Credit: Thermo Fisher Scientific - Elemental Analyzers and Phase Analyzers
Figure 3. Rietveld fit of Li₂CO₃ sample B (10 minutes). Image Credit: Thermo Fisher Scientific - Elemental Analyzers and Phase Analyzers
Table 1. Results of Rietveld refinement on Li₂CO₃ samples (3 σ in brackets). Source: Thermo Fisher Scientific - Elemental Analyzers and Phase Analyzers
| Phase |
Sample A (in wt%) |
Sample B (in wt%) |
| Na₂Mg(CO₃)₂ (Eitelite) |
0.7 (1) |
0.2 (1) |
| Li₂CO₃ (Zabuyelite) |
95.3 (2) |
99.5 (2) |
| Li₂(SO₄)·H₂O |
0.7(1) |
0.2 (1) |
| NaCl (Halite) |
3.3(1) |
0.1 (1) |
| KCl (Sylvite) |
0 |
0 |
| Total Li (XRD/Reference) |
18.0 / 17.2 |
18.7 / 18.5 |
Results
Figures 2 and 3 display the refinements of two samples of Li₂CO₃. The corresponding results are presented in Table 1. It is crucial to determine the quality of these samples as it directly impacts the suitability for further processing, necessitating a phase-pure material with a high total Li content.
The Li content can be indirectly deduced from Rietveld refinements by assuming stoichiometric phases with known Li content. Sample A contains 3.3 wt% NaCl and other minor phases, resulting in a total Li content of 18.0 wt%, which closely aligns with the reference value of 17.2 wt% obtained through chemical analysis.
On the other hand, Sample B is of superior quality, with minor contaminations contributing to a total Li content of 18.7 wt% (reference: 18.5 wt%). Both samples exhibit complete crystallinity.
Conclusion
X-Ray Diffraction (XRD) emerges as a potent technique for assessing the quality and purity of Li₂CO₃, enabling the indirect measurement of total Li content and the identification of contaminants that may impact material pricing and further processing.
The ARL X’TRA Companion XRD expeditiously collects Li₂CO₃ data in a mere 10 minutes, facilitating the detection of contaminants and quantifying the overall phase content.
The one-click Rietveld refinement based on a fundamental parameter approach is an extremely robust method with high reproducibility. Thanks to these qualities, the ARL X’TRA Companion is the perfect solution for any process or quality control task.
Reference
- N. Döbelin, R. Kleeberg, J. Appl. Crystallogr. 2015, 48, 1573-1580.
This information has been sourced, reviewed and adapted from materials provided by Thermo Fisher Scientific - Elemental Analyzers and Phase Analyzers.
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