In Situ Transmission Electron Microscopy for Ultrahigh Temperature Mechanical Testing of ZrO₂

This work demonstrates a novel approach to ultrahigh-temperature mechanical testing using a combination of in situ nanomechanical testing and localized laser heating. The methodology is applied to characterizing and testing initially nanograined 10 mol % Sc₂O₃-stabilized ZrO₂ up to its melting temperature. The results suggest that the low-temperature strength of nanograined, d < 50 nm, oxides is not influenced by creep. Tensile fracture of ZrO₂ bicrystals produce a weak-temperature dependence suggesting that grain boundary energy dominates brittle fracture of grain boundaries even at high homologous temperatures; for example, T = 2050 °C or T ≈ 77% T_melt. The maximum temperature for mechanical testing in this work is primarily limited by the instability of the sample, due to evaporation or melting, enabling a host of new opportunities for testing materials in the ultrahigh-temperature regime.