Influence of Yb3+ doping on phase stability and thermophysical properties of (Y1-xYbx)3Al5O12 under high temperature

In this work, Yb3+ was selected to replace the Y3+ in yttrium aluminum garnet (YAG) in order to reduce its thermal conductivity under high temperature. A series of (Y1-xYbx)3Al5O12 (x=0, 0.1, 0.2, 0.3, 0.4) ceramics were prepared by solid-state reaction at 1600 °C for 10 h. The microstructure, thermophysical properties and phase stability under high temperature were investigated. The results showed that all the Yb doped (Y1-xYbx)3Al5O12 ceramics were comprised of a single garnet-type Y3Al5O12 phase. The thermal conductivities of (Y1-xYbx)3Al5O12 ceramics firstly decreased and subsequently increased with Yb ions concentration rising from room temperature to 1200 °C. (Y0.7Yb0.3)3Al5O12 had the lowest thermal conductivity among investigated specimens, which was about 1.62 W m−1 K−1 at 1000 °C, around 30% lower than that of pure YAG (2.3 W m−1 K−1, 1000 °C). Yb had almost no effect on the coefficients of thermal expansion (CTEs) of (Y1-xYbx)3Al5O12 ceramics and the CTE was approximate 10.7×10−6 K−1 at 1200 °C. In addition, (Y0.7Yb0.3)3Al5O12 ceramic remained good phase stability when heating from room temperature to 1450 °C.