Monitoring Sulfur Stoichiometry During CLS Ceramic Processing
Calcium lanthanum sulfide (CLS), a solid solution of calcium sulfide (CaS) and lanthanum sulfide (La2S3), is being investigated for optical and thermoelectric applications. Maintaining appropriate sulfur stoichiometry presents a challenge during ceramic processing because changes in sulfur content can alter the material’s defect structure and properties.
A research paper published in Optical Materials Express examines the use of Raman spectroscopy as a complementary method for assessing deviations from stoichiometry in polycrystalline CLS ceramics. The researchers studied how changes during high-temperature processing affect the material’s Raman response and compared those observations with X-ray diffraction measurements.
Principal Findings
The researchers observed that changes in sulfur stoichiometry were associated with broadening of the A₁ Raman vibrational peak. The peak’s full width at half maximum provided an indicator of changes in the material’s local defect structure, while X-ray diffraction measurements revealed corresponding changes in the crystal lattice parameter.
These findings support the use of Raman spectroscopy as a complementary characterization technique for evaluating stoichiometric changes in polycrystalline CLS ceramics. The authors describe its potential for relatively rapid, semi-quantitative assessment during processing, while noting that further work is needed to establish more specific quantitative relationships between the observed spectral changes and individual defects.
Lorad’s Contribution
The study used calcium lanthanum sulfide powders supplied by Lorad Chemical Corporation. A chemist at Lorad is a co-author of the publication, which was conducted through a collaboration involving researchers from the University of Central Florida, government laboratories, and industry.
The research addresses characterization challenges relevant to the development of CLS powders and their processing into ceramic materials.
Read the Original Publication
The complete research paper, including its experimental methods, Raman spectra, X-ray diffraction results, and discussion of the proposed defect mechanisms, is available through Optical Materials Express.