La_(1-x)Sr_xFeO_(3-δ)(0≤x≤2/3)的低频内耗研究

Low-frequency internal friction study of La_(1-x)Sr_xFeO_(3-δ)(0≤x≤2/3) system

对A位掺杂的La1-xSrxFeO3-δ氧化物体系进行了低频内耗测量.研究发现此体系的内耗和模量-温度谱随Sr掺杂量(x)的不同而变化.当Sr含量x=0时,LaFeO3-δ体系的内耗和模量在测量温度范围内(-150—380℃)没有明显变化;而当x=0.2,0.25,1/3以及0.5时,掺杂样品均观察到一个与正交—三角相变对应的相变型内耗峰P1,且其峰温随x增加向低温移动.在x=0.25,1/3,0.5,0.6以及2/3的样品中还观察到一个弛豫型特征的内耗峰P2,此峰伴随着模量的变化,可归于畴壁的运动.进一步分析表明畴壁是受氧空位钉轧的.在x=0.5,0.6以及2/3样品的模量-温度谱上呈现出的模量急剧变化是与三角—立方铁弹性相变有关的.

La1-x SrxF eO3-δ systems were investigated by low-frequency internal friction method. The results show that the curves of the internal friction and modulus versus temperature vary with the Sr-dopant content （x）. For the undoped sample, no obvious change on the internal friction and modulus curves was observed between - 150-380℃, but the samples with x = 0.25,1/3, 0.5 and 0.6 show an intenal friction peak P1 with the feature of phase transitions, and the peak temperature moves toward lower temperature with incresing Sr content. This peak was suggested to be associated with a phase transition from rhombohedral to orthorhombic. The samples with x = 0.25,1/3,0.5,0.6 and 2/3 show a relaxation type peak P2 accompanied by a decrease in modulus, which can be attributed to the motion of domain walls whose mobility was contolled by the diffusion of oxygen vacancies. The samples with x = 0.5,0.6 and 2/3 show a rapid change in the curves of modulus versus temperature, which is related to a ferroelastie phase transition from rhombohedral to cubic.