effect of zirconia on crystallization of yttrium aluminum garnet precursor gel fibers

The zirconia-yttrium aluminum garnet (Zr-YAG) long fibers were successfully prepared through sol-gel method following by sintering at 1000oC, with aluminum powder, yttria, zirconium oxychloride and aluminum chloride as raw materials and polyvinylpyrrolidone as spinning additive. YAG phase was only observed in the fibers with smooth surface after sintering at 1000oC for 2 hours. However, a rough surface with an average grain size of 2 μm could appear when gel fibers were sintered at 1400oC for 6 hours. Calculated from Kissinger equation, the crystallization activation energy value (Ea) of Zr-YAG fibers was 59.69 kJ/mol. The Ea value is lower than YAG crystallization values by other authors.