Boron Nitride-Based Overcoat Thick Films for MoSi2 Planar Heating Elements

This work first reports a boron nitride‐based dielectric system that is designed for MoSi2–based planar heating elements patterned on a regular 96% alumina substrate. The dielectric system is expected to function as an overcoat layer mainly to protect the printed heating elements from environments and to reduce thermal stress induced during thermal heating through improved heat dissipation. The boron nitride (BN) pastes mixed with a low softening glass of calcium barium aluminoborosilicate were screen printed onto MoSi2 thick films and then fired at a temperature of 900°C. The addition of BN was found to increase the thermal conductivity considerably without detrimental chemical reactions with glass constituents. For instance, the thick film containing 30 wt% BN was regarded as a promising composition from the supporting evidences of good adhesion with MoSi2, an increased thermal conductivity of ∼31 W·(m·K)−1, and a high electrical resistance of 4.7 × 1010Ω.