Effect of La2O3 on Grain Refinement and Thermal Conductivity of 6 mol % Y2O3–ZrO2 Fibers

Abstract

ZrO₂ ceramic fibers have gained widespread study for the high temperature stability, low thermal conductivity and high mechanical properties. While for oxide fibers, grain growth is one of the limiting factors for long-term high temperature applications. In the present study, polycrystalline ZrO₂–6 mol % Y₂O₃ ceramic fibers with the addition of ~0–5 mol % La₂O₃ to refine the grain size were fabricated by the dry-spinning method. The XRD and Raman spectral results showed that the pyrochlore La₂Zr₂O₇ phase was formed as a second phase in the tetragonal zirconia fiber matrix. The formation of a second phase was an effective way to hinder grain growth for the competition phase effect and solid solution mechanism. With the addition of La₂O₃, the grain size decreased and concentrated in a smaller range of 50–250 nm compared with the ZrO₂–6 mol % Y₂O₃ matrix at 1400°C. Furthermore, the thermal conductivity of the fibers decreased with the additive of La₂O₃ less than 3 mol %. The present system is a promising candidate for high temperature applications.