Refractory metal (molybdenum, niobium, and tantalum) matrix composite materials in combination with refractory ceramics (alumina, zirconia, and mullite) are of particular interest for high-temperature applications, e.g., in refractory linings in the casting industry. [1] However, besides the high-temperature applicability, other aspects need consideration as well for the choice of material combination, such as: 1) the reaction between the metal and ceramic particles, 2) the chemical interaction with the environment, and 3) the thermal mismatch between the ceramic and the metallic phases. [2] The majority of the past publications dealt with so-called fine-grained refractory composites. [3][4][5][6][7] However, their disadvantages are high shrinkage on sintering, thus resulting in limited thermal shock ability. The refractory metals Nb and Ta are promising candidates for application with Al 2 O 3 due to their similar thermal expansion behavior. Wang et al. [8] and White et al. [9] showed for temperatures between 1000 and 2000 K a similarly linear increase of the linear thermal expansion coefficient for the three elements, with 8.8 to 11.2 Â 10 À6 K À1 for α-Al 2 O 3 , [8] 8.3 to 10.4 Â 10 À6 K À1 for Nb, and 7.1 to 8.4 Â 10 À6 K À1 for Ta. [9] Recently, Zienert et al. [10] demonstrated the fabrication of coarse-grained refractory composites based on alumina with niobium or tantalum, while Weidner et al. [11] reported first mechanical properties at high temperatures (1300-1500 °C) under compressive load. In these coarse-grained refractory composites, alumina with different particle classifications from 0-20 μm up to 2-5 mm (with different volume