Sintering Properties And Microstructure Of Submicron (Y_1-xLa_x)₂O₃ Powders Prepared By The Citrate Method

The submicron(Y_1-xLa_x)₂O₃ powders were prepared by the citrate method using Y?NO₃?₃?6H₂O,La?NO₃?₃?6H₂O,citric acid,ethanediol and deionized water as the raw materials.The preparation process of the powders,the choice of the dispersants and the microstructure of the(Y_1-xLa_x)₂O₃ powders were discussed.Then the sintering properties of the prepared powders were discussed.The results are as follows:?1?When the mol ratio of citric acid to metal cation is more than 1.5:1,the mol ratio of ethanediol to metal cation is more than 1.5:1 and the mol ratio of deionized water to metal cation is 15:1,the size of the prepared powders is small and the dispersion is good.?2?The best mass percent of PEG400 is 4 wt%,and the primary particle size of the powders calcined at 1100? is about 85 nm,while the best mass percent of oleinic acid is 2 wt%,and the primary particle size of the powders calcined at 1100? is about 75 nm.It is also exhibited that the size of the powders become bigger as the calcinations temperture rises.It is also exhibited that the dispersity of the powders which using the oleinic acid as the dispersant is better than PEG400,because the coacervate peak of powders which using the oleinic acid is lower.?3?When the(Y_1-xLa_x)₂O₃ powders were prepared by the citrate method,the La₂O₃ can make the powders size smaller,and t he effect is more obvious as the La₂O₃ is more,and the La₂O₃ solution limit is about x=0.2.When adding excess La₂O₃,the powders will appear the second phase.?4?When the ceramics were prepared by solid state section,the La₂O₃ need after 1500 ? heat treatment before being used,and then used immediately,because the La₂O₃ is easy to absorb moisture in the air to form La?OH?₃.The La₂O₃ can obviously reduce the sintering temperature of ceramic,and when x=0.05⁰.15,the density of the ceramic sintering temperature is 1650?.The La₂O₃ solution limit is before x=0.15,and when x is greater than 0.15,the ceramic appeared of mixed phase.?5?The(Y_0.9La_0.1)₂O₃ ceramics first 1500? sintering in air then sintering in vacuum furnace,has a more compact structure.When the(Y_1-xLa_x)₂O₃ ceramics were sintered at 1600? in air,the La₂O₃ solution limit is around x=0.15.When the solid solution under the limit,with the increase of x value,ceramic more dense;More than ceramic solid solution limit,with the increase of x,because of the influence of the second phase,porous ceramics has become loose.The particles of the powders is around 60¹50 nm after 1200 ? calcination,which is the relatively appropriate particle size for ceramic sintering.