Fine-Grain High-Performance Densified Oxide Fibers Produced by Open Ultrafast High-Temperature Sintering

The considerable grain growth occurring during the long-term high-temperature sintering of polycrystalline oxide fibers negatively affects their mechanical properties, which highlights the need for alternative sintering methods. Herein, open ultrafast high-temperature sintering (OUHS) in air, characterized by rapid heating/cooling (>10000 K min^-1) and a short high-temperature holding time (<10 s), is used to produce 3 mol% yttria-stabilized zirconia continuous fibers with coherent boundaries forming robust connections between fine grains. The tensile strength of these fibers (2.33 GPa on average, sintering temperature = 1673 K) notably exceeds that of their counterparts produced by traditional sintering (1.17 GPa). The effects of pores on fiber mechanical properties are analyzed using experimental and theoretical methods. For a versatility demonstration, OUHS is applied to several types of polycrystalline oxide fibers (HfO₂, Al₂O₃, TiO₂, Y₂O₃, and La₂Zr₂O₇), considerably improving their mechanical properties and enabling crystalline phase control, which demonstrates the suitability of this procedure for the development of high-performance materials.