A deeper insight into the design of creep resistant α-Al2O3/YAG fibers: effects of seeding material and thermal treatment on the structural, microstructural and mechanical properties

Polycrystalline α-alumina / yttrium-aluminum garnet (YAG) fibers were prepared from aqueous solutions of aluminum formoacetate and yttrium acetate, with α-Al2O3 nanoparticles as a seeding material. α-Al2O3/YAG fiber production was achieved via dry-spinning, using polyvinylpyrrolidone as a spinning aid, followed by calcination and sintering of as-spun fibers at various temperature, dwell time and heating ramp. X-ray diffraction analysis evidenced the formation of transitional Al2O3 and yttrium-aluminum perovskite (YAP) phases (1000-1300 °C) before a full conversion to α-Al2O3 / YAG (76 / 24 wt%) at 1500 °C. Full densification required temperatures of at least 1400-1500 °C with a sufficient dwell time (30 min), while increasing sintering temperature induced grain growth. Depending on the thermal treatment, tensile strength and creep factor m of the related fibers could be tailored, either to higher strength at 1400 °C (up to 1149 MPa, m = 0.57) or higher creep at 1500 °C (up to 906 MPa, m = 0.69).