Characterization of synthetic yellow diamonds used in the cutting and polishing industry

This study investigates the physico-chemical properties of synthetic yellow diamonds used in the cutting and polishing industry, focusing on four High-Pressure High-Temperature (HPHT) diamond batches with identical average grain sizes but different mechanical properties and industrial applications, sourced from various suppliers. The analysis encompasses their morphology, crystal structure, chemical composition, and thermal and mechanical durability. Techniques such as microscopy, XRF, XRD, SEM, Raman spectroscopy, FTIR, UV analysis, and polariscope measurements were utilized. The findings reveal significant variations in batch quality, largely influenced by the morphological integrity of cube-octahedral crystals. Chemical analysis identified trace elements, such as Fe, Al, and Cr, which affect crystal growth and defect formation during synthesis. Mechanical testing showed that one batch exhibited superior resistance due to its optimal morphology and minimal defects, while two lower-cost batches demonstrated moderate resilience. Thermal treatment results indicated that carbide-forming elements enhance resistance to graphitization, a critical factor for high-temperature applications. Although the findings align with general commercial practices, the justification for pricing discrepancies remains unclear, emphasizing the need for detailed batch characterization in the industry.