Effect Of Multiple Doping On The Structure And Thermophysical Properties Of Gadolinium Zirconate Ceramic Material

This research chose the pyrochlore Gd₂Zr₂O₇ ceramic material with good comprehensive thermophysical properties as the research object.In addition,because of the characteristic that the ratio of R(Gd³⁺)/R(Zr⁴⁺)in Gd₂Zr₂O₇ is at the critical point of phase transition,so in this paper,we select Nb⁵⁺with a smaller ion radius than Zr⁴⁺to partially replace Zr⁴⁺to maintain the ratio of R(Gd³⁺)/R(Zr⁴⁺)in the pyrochlore structure range 1.46?R(Gd³⁺)/R(Zr⁴⁺)?1.78,and then study the effect of Nb⁵⁺doping on the thermal expansion coefficient and thermal conductivity of Gd₂Zr₂O₇ ceramic material.Then,studying the effect of the co-doping about Nb₂O₅,CuO and Nb₂O₅,Fe₂O₃ on thermal expansion coefficient and thermal conductivity after doping,meanwhile,the behavior of co-doping also matain the A₂B₂O₇ chemical standard formula in the co-doped ceramic material.In this paper,different oxides were selected to dope the Gd₂Zr₂O₇ ceramic material,which were integrated by high-temperature solid-phase reaction method.Meanwhile,the XRD,Raman spectrometer,SEM,high temperature thermal expansion instrument and laser thermal instrument are used to analyze the crystal structure,micromorphology,thermal expansion coefficient and thermal diffusion coefficient,and the bulk density and heat capacity of ceramic material are calculated according to Archimedes'principle and Neumann-Kopp's law.The research results are as follows:The results of Nb⁵⁺doping,Nb₂O₅,CuO co-doping,and Nb₂O₅ and Fe₂O₃ co-doping of the Zr⁴⁺site in Gd₂Zr₂O₇ show that they all have a single cubic pyrochlore structure and a dense unit cell structure.Thermal physical performance results show that:in the range of room temperature to1300?,the thermal expansion coefficient of Gd₂(Zr_1-xNb_x)₂O_7+x+x ceramic samples and Gd₂(Zr_1-3x/2Nb_xCu_x/2)₂O₇ ceramic samples gradually decreases as the increase of the oxide doping amount.The thermal expansion coefficient of the Gd₂(Zr_1-2xNb_xFe_x)₂O₇ ceramic sample presents the phenomenon of increasing first and then decreasing with the increase of the doping amount of Nb₂O₅ and Fe₂O₃.Then the thermal conductivity of Gd₂(Zr_1-xNb_x)₂O_7+x+x ceramic materials changes from 1.5259-1.8076 W/?m·K?at room temperature to 1.27-1.45 W/?m·K?at 1000?with the increase of Nb₂O₅ doping amount.The thermal conductivity of the specimens decreases over the temperature range about25?-1000?,which decreases from 2.01 W/?m·K?to 1.10 W/?m·K?,and as the doping amount of Nb₂O₅ and CuO increases,the thermal conductivity of the ceramics decreases firstly and then increases.And The thermal conductivity of Gd₂(Zr_1-2xNb_xFe_x)₂O₇ solid solution shows a downward trend in the entire temperature range.It increases with the increase of the doping amount of Nb⁵⁺and Fe³⁺in 0-0.05 mol,when the doping amount reaches 0.06 mol,the thermal conductivity has a slight decrease than it is 0.05 mol.The results show that Gd₂(Zr_1-3x/2Nb_xCu_x/2)₂O₇ ceramic materials have the potential to be candidates for YSZ materials.