Synthesis And Properties Of Lanthanum Molybdate Electrolyte

Industrial emissions and energy consumption have become urgent environmental problems due to their serious damage to ecosystems and human health.Fuel cell as one of the low carbon economy technology has aroused great interest.The new lanthanum molybdate?La₂Mo₂O₉?ion conductor has been extensively studied because of its superior electrical properties in fuel cells.It shows the cubic?-La₂Mo₂O₉ phase and the monoclinic?-La₂Mo₂O₉ phase at high temperature and low temperature,respectively.The transformation from the?to?phase at 580?will reduce the conductivity by several orders of magnitude.Previous studies have found that doping modification at Mo site can effectively inhibit the occurrence of phase transition.In this paper,La₂Mo_2-xNi_xO_9-??La₂Mo_2-xGe_xO_9-?and La₂Mo_2-xMg_xO_9-??0?x?0.4?samples obtained by Mo doping were used to study the electrical properties of La₂Mo₂O₉doped materials.Firstly,we prepared La₂Mo_2-x-x Ni_xO_9-??0?x?0.4?samples by solid phase method,and then studied the crystal structure?microscopic morphology and electrical properties of the samples by means of XRD?SEM and EIS.The above researches showed that Ni²⁺doping at Mo site could effectively improve the conductivity of materials and effectively inhibit the phase change reaction of lanthanum molybdate materials.Since the radius of Ni²⁺is larger than that of Mo²⁺,the lattice parameters and oxygen ion vacancy of the sample increased after the addition of Ni²⁺,so that the conductivity of the ionic conductor increased gradually.However,the lattice mutation caused by the excessive addition of Ni²⁺would hinder the moving oxygen vacancy and made the conductivity decrease instead of increasing.Therefore,it could be concluded that x=0.3 was the optimal doping amount.Secondly,La₂Mo_2-xGe_xO_9-?and La₂Mo_2-xMg_xO_9-??0?x?0.4?samples were prepared and characterized by the same method.The experimental results showed that the sample material La₂Mo_1.8Ge_0.2O_8.8.8 and La₂Mo_1.8Mg_0.2O_8.6.6 had the highest conductivity due to the maximum oxygen ion channel at x=0.2.The conductivity does not change suddenly at 580?,As the doping continues to increase,lattice mutation occurs in the crystal to reduce the oxygen ion vacancy and decrease the conductivity.Therefore,we conclude that the samples La₂Mo_1.7Ni_0.3O_8.4?La₂Mo_1.8Ge_0.2O_8.8.8 and La₂Mo_1.8Mg_0.2O_8.6.6 have a good development prospect in the direction of medium-temperature solid oxide fuel cell as electrolyte materials.