Toughening Research Of Nd₂Zr₂O₇ Ceramic For Thermal Barrier Coatings

Thermal barrier coatings?TBCs?have been applied in hot components of aero engine to provide thermal insulation,which permit higher operating temperatures and superior energy conservation.Nd₂Zr₂O₇ is considered to be a new potential thermal barrier coating candidate for ultrahigh temperature application,but the lower fracture toughness limits its application.In this study,the toughening of Nd₂Zr₂O₇ thermal barrier coating material toughening was researched.The phase composition and the phase composition and thermo-mechanical properties of Sc₂O₃ and Fe₂O₃ doped in Nd₂Zr₂O₇ ceramic were investigated,which would provide the foundation for new potential TBCs.The(Nd_1-xSc_x)₂Zr₂O₇?x=0,0.025,0.05,0.075,0.1?ceramic power was synthesized by chemical co-precipitation and calcination method then they was cold pressed into disc compacts and high temperature sintered.The phase composition thermal expansion coefficient and fracture toughness of(Nd_1-xSc_x)₂Zr₂O₇?x=0,0.025,0.05,0.075,0.1?ceramic were investigated.The result shows that when x?0.075,(Nd_1-xSc_x)₂Zr₂O₇ exhibited pyrochlore structure and with the increase of the Sc₂O₃ content,the disordering degree of the pyrochlore in the compounds increased.When x=0.1 there exists fluorite phases.In(Nd_1-xSc_x)₂Zr₂O₇ series,(Nd_0.925Sc_0.075)₂Zr₂O₇ exhibited the largest TEC,while the toughness of the compounds increased with increasing of the Sc₂O₃ content.The related mechanisms were discussed based on the crystal structure analysis.Considering the TEC and toughness,10 mol%Sc₂O₃ was suggested as the optimal doping content for Nd₂Zr₂O₇ceramic.Nd₂Zr₂O₇ powder was synthesized by chemical co-precipitation and calcination method.The x mol%?x=10,20,30,40,50?Fe₂O₃ doped Nd₂Zr₂O₇ powder was prepared by high temperature solid-state reaction method then they was cold pressed into disc compacts and high temperature sintered.The phase composition and fracture toughness were investigated.The result shows that Nd₂Zr₂O₇ exhibit pyrochlore structure.With increasing of the Sc₂O₃ content,there is fluorite phase whose content increases,while(Nd_0.6Fe_0.4)₂Zr₂O₇ and(Nd_0.5Fe_0.5)₂Zr₂O₇ only exist fluorite phase.In(Nd_1-xFe_x)₂Zr₂O₇ series,with increasing of the Sc₂O₃ content,hardness and toughness firstly increase rapidly.When Fe₂O₃ doped amount to 30 mol%,it has the biggest hardness and toughness.With the further increase of Fe₂O₃,hardness and toughness begin to decrease.The improvement of hardness and toughness might be attributed to a combination of several toughening mechanisms which included the increase of fracture energy,disordering and compressive stress.