Experimental Intvestigation Of Subsolidus Phase Relation Of Gd₂O₃-Mn₃O₄/SrO-CoO_x

Perovskite oxide,with its unique crystal structure,can be used in many fields such as solid fuel cells,sensors and high-temperature heating materials,and has become a research hotspot and focus in the fields of chemistry,physics and materials.Phase diagram is a graphic of the phase state,temperature and composition of a material.It is an effective way to express the properties of a material directly and conveniently.This paper is mainly divided into two parts.The first part is the experimental research on the offline phase relationship of subsolidus phase of Gd₂O₃-Mn₃O₄-CoO_x,and the second part is the experimental research on the offline phase relationship of subsolidus phase of Gd₂O₃-Sr O-CoO_x.In the first part and the second part,the oxide samples were prepared by solid reaction method respectively.The phase relationship of the system under the subsolidus phase was determined by X-ray diffraction method and scanning electron microscopy method.The first part is the phase relationship under subsolidus phase of ternary system Gd₂O₃-Mn₃O₄-CoO_x.The experimental results show that the system is composed of 6single-phase regions,6 two-phase regions and 3 three-phase regions,and it is confirmed that there are 5 binary compounds,namely Gd Mn O₃,Gd CoO₃,Gd Mn₂O₅,Co Mn₂O₄and Co₂Mn O₄.The subsolidus phase range of 4 solid solutions was determined by the phase disappearance method.The first belong to orthorhombic system,space group Pnma（62）of solid solution Gd Co_1-xMn_xO₃（0≤x≤1）,in which the point x=0.5 of X-ray diffraction data was used to structure refinement by software Fullprof,and the results obtained that the composition point of x=0.5 belong to orthorhombic system,space group Pnma（62）,which refer to the lattice constant of a=5.5779（3）（?）,b=7.5523（4）（?）,c=5.3001（3）（?）of compound Gd Co_0.5Mn_0.5O₃;The other is the solid solution T-Co_3-zMn_zO₄（2.1≤z≤3.0）,which belong to tetragonal system of space group I4₁/amd（141）;The third is the solid solution C-Co_3-zMn_zO₄（0.975≤z≤1.05）with cubic crystal system and space group ofFd 3^-m（227）.The fourth is the solid solution Co_1-yMn_yO（0≤y≤0.05）with cubic crystal system and space group of Fm^-3m（225）.The second part is the phase relationship subsolidus phase relations of the ternary system Gd₂O₃-Sr O-CoO_x.The experiment shows that the system consists of 11 single-phase regions,3 two-phase regions and 12 three-phase regions.The system confirmed 5 binary compounds and 3 ternary compounds,namely Gd CoO₃,Gd₂Sr O₄,Sr₆Co₅O₁₅,Sr₁₄Co₁₁O₃₃,Sr₄Co₃O₉,Gd Sr CoO₄,Gd₂Sr Co₂O₇,Gd_0.33Sr_0.67CoO_2.82.The system confirmed that Sr₃Co₂O₆and Sr₂Co₂O₅was high-temperature phase,while compounds Sr₄Co₃O₉,Sr₆Co₅O₁₅and Sr₁₄Co₁₁O₃₃were room temperature stable phase.The solid solution range of two solid solutions was determined by the phase disappearance method.The first is belong to tetragonal system,space group of I4/mmm（139）of solid solution Gd_1-ySr_1+yCoO₄（-0.19≤y≤0.34）,in which the composition of y=0.19 of X-ray diffraction data was used to structure refinement by software Fullprof,resulting to point y=0.19 is tetragonal crystal system,space group of I4/mmm（139）,the lattice constant is a=b=3.75162（7）（?）,c=12.2671（2）（?）with the compound Gd_0.81Sr_1.19CoO₄.The second is the solid solution Gd_1-xSr_xCoO₃（0.6≤x≤0.9）with tetragonal crystal system and the space group I4/mmm（139）.