Effect of Nb^(5+)and Cu^(2+)codoping on thermal properties of Gd_(2)Zr_(2)O_(7)ceramic

In this work,Nb^(5+)and Cu^(2+)were selected to partially substitute Zr4+in Gd_(2)Zr_(2)O_(7)for studying the phase structure,microscopic morphology and thermal properties.Gd_(2)(Zr_(1-3 x/2)Nb_(x)CU_(x/2))_(2)O_(7)(x=0,0.05,0.1,0.15,0.2,0.25)ceramic materials were synthesized by high-temperature solid-state reaction method.The results show that the Gd_(2)(Zr_(1-3 x/2)Nb_(x)Cu_(x)/2)_(2)O_(7)ceramics present cubic pyrochlore structure with clear grain boundaries and dense cell structure.And the thermal expansion coefficient of Gd_(2)(Zr_(1-3 x/2)Nb_(x)Cu_(x/2))_(2)O_(7)ceramics gradually decreases because of the incorporation of Nb^(5+)and Cu^(2+)into Zr-site in Gd_(2)Zr_(2)O_(7).Meanwhile,its thermal conductivity decreases firstly and then increases with the doping of Nb^(5+)and Cu^(2+),which reaches the lowest value for the composition of Gd_(2)(Zr_(0.85)Nb_(0.1)Cu_(0.05))_(2)O_(7).