Thermo-physical properties and ferroelastic toughening of non-transformable t'-yttria-stabilized hafnia-zirconia solid solution

HfO 2 is an attractive thermal barrier coating material component due to its similarity to ZrO 2 and its high phase structure transformation temperature. However, the difficulty of stabilizing HfO 2 in tetragonal phase by rare element doping and non-satisfying fracture toughness greatly limit its application. We report here the structural, thermophysical properties, ferroelastic toughening mechanism and fracture toughness of plasma-sprayed Y 2 O 3 stabilized ZrO 2 -HfO 2 solid solution ((Zr 1- x Hf x ) 0.9 Y 0.1 O 1.95 , YSHZs, x = 0.1, 0.3, 0.5). A new ferroelastic material is found, YSHZ ( x = 0.5) possesses relatively high fracture toughness of 3.5 +/- 0.2 MPa & sdot; m 0.5 through the ferroelastic domains swerving under the stress field of a crack. Moreover, YSHZ ( x = 0.5) possesses relatively low thermal conductivity of 1.35 W & sdot; m - 1 & sdot; K - 1 at 1200 degrees C and useable thermal expansion coefficients of 10.75 x 10 -6 K -1 . The combination of properties (especially ferroelasticity) bodes well and makes YSHZ ( x = 0.5) as a potential TBC material in gas turbine engines application.