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.