Controlled Synthesis Of Bismuth Oxide With Various Crystal Phase And Its Influence On Sintering Properties Of YSZ

Solid electrolyte material is a solid material with an ionic conductivity and has a wide application in new solid cells,high temperature oxide fuel cells,ionic conductivity sensor and so on.Yttria Stabilized Zirconia(YSZ),one of the solid electrolyte materials,has a wide attraction due to its good oxygen ionic conductivity and mechanical property,and it has been applied commercially.One of the most important application of YSZ is the Solid Oxide Fuel Cells(SOFCs).To even a better performance,however,there two problems must be solved:(1)YSZ has a very high sintering temperature which usually is more than 1500?;(2)As a electrolyte material working in SOFCs,YSZ need a high temperature to start work.These high temperatures increase the difficulty of technic and the cost of application.To solve these issues,the past studies found that the Bi2O3 could reduce the sintering temperature and enhance the oxide ionic conductivity to reduce the work temperature as an agent.However,these studies use mechanical method that has a high cost and is not suitable for commercial application,and the influences of phase and morphology of Bi2O3 on the YSZ as well as the distribution of Bi2O3 on the grain boundary of YSZ were not considered.In this paper,the system of bismuth oxide(Bi2O3)composited YSZ material was studied.Starting from powders preparation,the different phase and morphology Bi2O3 composited YSZ powders were synthesized aiming at the design of microsture of Bi2O3/YSZ samples to reduce the sintering and work temperature of YSZ.The rod-like a-Bi2O3/YSZ composited powders were synthesized via the chemical precipitation method.It was found that the one dimension rod-like Bi2O3 obeyed the screw dislocation mechanism that is controlled by chemical kinetic during the growth,during which the screw dislocation is the growth units of the one dimension growth of Bi2O3.The sintered samples had homogenous composition.The addition of Bi2O3 effectively promoted the sintering process of YSZ and formed various solid solution to improve the ionic conductivity of samples.When adding 5%mol Bi2O3,the rod-like a-Bi2O3/YSZ composited powders were sintered at 1150?to 1200 C and the dense electrolyte material was obtained.The netlike Bi2O3 and Bi2O3 coated YSZ powders were synthesized using a sol-gel method.The formation of netlike structure is ascribed two aspects during the calcining process:the rate of the evaporation of methoxyethanol and the rate of the formation of Bi2O3,and finally the homogenous Bi2O3 coated YSZ powders were obtained.The addition of Bi2O3 effectively promoted the sintering process of YSZ powders and formed various solid solution.Moreover,due to the netlike morphology,the Bi2O3 formed a coat on the surface of YSZ grain and distributed on the YSZ grain boundary homogeneously.The ?-Bi2O3 and ?-Bi2O3/YSZ powders were synthesized using a chemical precipitation method.The ?-Bi2O3 was fabricated and formed a tetrahedron morphology using the nucleation,ripening,oriented attachment,and self-assembly process.The synthesized ?-Bi2O3/YSZ powders had a good flow ability and was easy to mold.The addition of Bi2O3 effectively promoted the sintering process of YSZ and formed various solid solution.When adding 15%mol Bi2O3,the ?-Bi2O3/YSZ composited powders were sintered at 1150 ? and the dense sample was obtained.For solid electrolyte material application,the §-Bi2O3/YSZ composited powders was the best choice among three composited powders.When having 5%mol a-Bi2O3,the sample could have highest relative density and the Bi2O3 could be doped in YSZ material at 1150 0C to 1200 ?.There was a potential application in netlike?-Bi2O3/YSZ composited powers,but the suitable molding method need to be found to increase the density.The ?-Bi2O3/YSZ composited powders have many shortages.