The preparation method is considered proprietary, however, this compound has not undergone passivation. This product is ≥99.5% Lithium nitride and is tested for impurities.
Please see the Product Sample Certificate of Analysis to view trace metal testing:
https://www.sigmaaldrich.com/certificates/sapfs/PROD/sap/certificate_pdfs/COFA/Q14/399558-BULKMKCT0250.pdf