Anisotropic secondary phases in Mo(Si,Al)2 ceramics investigated by neutron diffraction

Journal article, 2026

Mo(Si,Al)2 ceramics offer improved oxidation resistance over MoSi2, enhancing performance in resistive heating elements. However, formation of the anisotropic secondary phase Mo5(Si,Al)3 during processing also promotes crack formation. While coefficients of thermal expansion (CTE) data exist for the Mo(Si,Al)2 matrix phase and Al-free Mo5Si3, it is unclear how Al-incorporation affects the thermal expansion behaviour of Mo5(Si,Al)3. In this work, high-temperature neutron diffraction was used to measure phase-specific anisotropic thermal expansion in Mo(Si,Al)₂ ceramics, with and without Al-addition. The Mo₅(Si,Al)₃ phase was confirmed to be anisotropic, independent of Al-content. This study provides the first CTE-data for Mo₅(Si,Al)₃ embedded in the matrix phase and with Al-addition, offering valuable insight for designing reliable heating elements for high-temperature industrial applications.