In-situ synthesis of Y 2 W 3 O 12 within a Co-based superalloy powder mixture In this work, the synthesis of the negative thermal expansion ceramic Y 2 W 3 O 12 within a Co-based superalloy was analyzed in detail. On the basis of thermal analysis of the synthesis from the feedstock powders Y 2 O 3 and WO 3 further experiments were conducted. Thermal behavior and stability of different mixtures of the powders Y 2 O 3 , WO 3 and the Co-based superalloy were investigated. The qualitative and quantitative results of the synthesis separately and within the superalloy are presented as achieved by energy dispersive X-ray analysis, X-ray powder diffraction, differential thermal analysis and thermal gravimetric analysis. It was found that the synthesis of yttrium tungstate inside the Co-based superalloy is possible with a defined temperature program and a simple basic production process of powder mixtures.