t-ZrO2 toughened Al2O3 free-standing films and as oxidation mitigating thin films on silicon nitride via colloidal processing of flame made nanopowders (NPs)

Zirconia toughened aluminas (ZTAs) are one of the most important engineering ceramics with high melting points, excellent mechanical strength, and chemical stability, and are commonly used as wear resistant and high-temperature components, as prosthetic implants, and electric circuit substrates. In this work, we explore methods of processing fine-grained, dense, thin, free-standing (ZrO2)(x)(Al2O3)(1-x) films (x = 0-50 mol%, similar to 40 mu m thick) by sintering flame made nanopowders (NPs) to optimize the t-ZrO2 content, sinterability, and microstructures under select conditions (1120 degrees C-1500 degrees C/5 h in O-2 or 95%N-2/5%H-2). In all cases, the final sintered products retain t-ZrO2 with average grain sizes (AGSs) of 0.1-1 mu m. ZTA film thicknesses were increased to similar to 200 mu m to assess potential as electronic substrates. Excellent fracture toughness (24 MPa m(1/2)) and small AGSs of 0.7 mu m were found for similar to 200 mu m thick ZTA films sintered at 1500 degrees C/5 h/N-2/H-2 using a three-step binder burnout process. Furthermore, we show that homogeneous ZTA thin films (<5 mu m thick) can be sintered on Si3N4 substrates (thickness approximate to 300 mu m) to provide physical protection against oxidation under extreme conditions (1500 degrees C/1 h/O-2), offering additional practical utility for high-temperature ceramics and power electronic substrates.

Automated summary

Zirconia toughened aluminas (ZTAs) are important engineering ceramics with high melting points, excellent mechanical strength, and chemical stability. Through sintering flame made nanopowders, fine-grained, dense, thin ZTA films were successfully processed with optimized microstructures and sinterability under select conditions.