The Inhibitory Effect of Hafnium Oxide on Grain Growth in Yttrium Aluminum Garnet Composite Fiber

Yttrium aluminum garnet (YAG, Y₃Al₅O₁₂) fibers are promising materials for high-power lasers and high-temperature structural materials, and it is anticipated that the improvement in the stability of grain size would extend their service life at high temperatures. In this work, YAG-HfO₂ composite ceramic fibers were obtained by the solution blow spinning of YAG-HfO₂ composite precursor and sintering in steam. The effect of HfO₂ on the crystal phase transition and grain growth of YAG-HfO₂ fibers was further studied by in situ X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), and Transmission Electron Microscope (TEM). The results show that the HfO₂ addition increased the crystallization temperature of the YAG phase from 900 °C to 950 °C and reduced the crystal size at 1400 °C from 41.9 nm to 31.8 nm. The HfO₂ grains were distributed at the boundary of YAG grains, which enabled the fiber to maintain its dense structure and uniform grain size even at 1500 °C, exhibiting excellent high-temperature grain size stability of composite fibers.