The difficulty of reducing the diameter of lutetium oxide (Lu₂O₃) continuous fibers below 50 μm not only limits the flexibility of the sample but also seriously affects their application and development in high-energy lasers. In this work, a Lu-containing precursor with high ceramic yield was used as raw material, fiberized into precursor fibers by dry spinning. The pressure-assisted water vapor pretreatment (PAWVT) method was creatively proposed, and the effect of pretreatment temperature on the ceramization behavior of the precursor fibers was studied. By regulating the decomposition behavior of organic components in the precursor, the problem of fiber pulverization during heat treatment was effectively solved, and the Lu₂O₃ continuous fibers with a diameter of 40 μm were obtained. Compared with the current reported results, the diameter was reduced by about 50%, successfully breaking through the diameter limitation of Lu₂O₃ continuous fibers. In addition, the tensile strength, elastic modulus, flexibility, and temperature resistance of Lu₂O₃ continuous fibers were researched for the first time. The tensile strength and elastic modulus of Lu₂O₃ continuous fibers were 373.23 MPa and 31.55 GPa, respectively. The as-obtained flexible Lu₂O₃ continuous fibers with a limit radius of curvature of 3.5–4.5 mm had a temperature resistance of not lower than 1300 ℃, which established a solid foundation for the expansion of their application form in the field of high-energy lasers.

Yttria-stabilized zirconia (YSZ) fiber composites are highly efficient thermal insulating materials; however, the poor thermal shock resistance limits their versatile applications. In the present study, YSZ fiber was mixed directly with Al₂TiO₅ fiber, which had an extremely low thermal expansion coefficient, to prepare YSZ-Al₂TiO₅ (ZAT) fiber composites by compression molding and heat treatment. The minimum thermal expansion coefficient of the prepared ZAT fiber composites was measured to be 7.74×10^-6 K^-1, which was 26% lower than that of the YSZ fiber composites (10.42×10^-6 K^-1). It was shown that the prepared ZAT fiber composites maintain the integrity after undergoing 51 thermal shock cycles between 1100 ℃ and room temperature. Whereas, YSZ fiber composites burst immediately after only one thermal shock cycle under the same condition. In addition, the ZAT fiber composites also exhibit considerable mechanical and thermal insulating performance.