La_(2)CuO_(4)阴极薄膜的相转变及其对电化学性能的影响

Phase Transformation of La_(2)CuO_(4) Cathode Film and Its Influence on Electrochemical Properties

通过调控薄膜的沉积条件,探索La_(2)CuO_(4)的晶体结构对电化学性质的影响。采用脉冲激光沉积设备在YSZ(100)单晶基底上沉积一系列La_(2)CuO_(4)薄膜,通过调节沉积时的氧压,制备了不同晶体结构的La_(2)CuO_(4)薄膜。研究表明,沉积氧压的变化使薄膜晶体结构发生相转变,从T′相→T*相→T相。T′相为沿着c轴择优生长的单晶四方相,且表现出较大的界面极化电阻,在850℃的Rp值为2.351Ω·cm^(2)。T*相为T′相和T相的混合相,在850℃的电阻值介于T′相和T相之间。T相为正交相,相对于其它相结构表现出较低的界面极化电阻,沉积氧压为26.60 Pa下制备的T相在850℃的电阻值为0.783Ω·cm^(2),比T′相的电阻值低近67%。并且,正交相表面有相对较高的氧空位浓度,有利于氧气的吸附和扩散,加速了阴极的氧还原反应。因此,具有正交对称性的La_(2)CuO_(4)的电化学性质优于其它对称性。这一结果也表明可以通过改变薄膜材料的晶体结构,降低界面极化电阻,提高阴极薄膜的电化学性能。

In this paper,the effect of crystal structure of La_(2)CuO_(4)on electrochemical properties is investigated by controlling the deposition conditions of thin films.A series of La_(2)CuO_(4)films is deposited on the YSZ(100)single crystal substrate by pulsed laser deposition,and La_(2)CuO_(4)films with different crystal structures are prepared by adjusting the oxygen pressure during deposition.The study shows that the crystal structure of the thin film changes from T′phase→T*phase→T phase with changing oxygen pressure.T′phase is the single crystal with a tetragonal symmetry which prefers growing along the c axis and shows a larger polarization resistance.The value of Rp is 2.351Ω·cm^(2)at 850℃.T*is a mixed phase whose resistance value at 850℃is between T′phase and T phase.T phase is orthorhombic which shown lower polarization resistance compared with the other phase structure,and the Rp value of T phase is 0.783Ω·cm^(2)when the oxygen pressure is 26.60 Pa and the temperature of 850℃,which is about 67%lower than the Rp value of T′phase.Besides,the orthorhombic phase surface has relatively higher oxygen vacancy concentration,which is conducive to the absorption and diffusion of oxygen and enhances the oxygen reduction reaction.Therefore,the La_(2)CuO_(4)with orthorhombic structure has more excellent electrochemical property than that of other symmetries.The results also show that the polarization resistance can be reduced by changing the crystal structure of the material,and the electrochemical performance of the cathode film can be improved.