La_2Cu_(1-x)Li_xO_(4+δ)体系低频内耗研究

Research on Low-Frequency Internal Friction La_2Cu_(1-x)Li_xO_(4+δ) Compounds

采用强迫振动方法对La2Cu1-xLixO4+δ(0.02≤x≤0.15)系列氧化物超导体的母体化合物的低频内耗和模量进行了研究.结果表明,当x=0.02,0.05时,La2Cu1-xLixO4+δ在250 K附近存在一个弛豫型内耗峰P1,为共价氧对形式的额外氧跳跃弛豫运动的结果;当x=0.10,0.15时,La2Cu1-xLixO4+δ除了存在内耗峰P1外,在200 K附近还出现了内耗峰P2;La2Cu1-xLixO4+δ在高温区域的模量反常现象反映了体系的正交与四方结构转变,其相变温度随Li的掺杂量的增加而向低温区域移动.

The low-frequency internal friction Q^-1 and relative shear modulus E of La2Cu1-xLixO4＋δ（0.02≤x≤0.15） compounds were studied by means of force fibration.For x=0.02 and 0.05,only one relaxation peak exists around 250 K and this peak is due to the hopping of O pairs.For x=0.1 and 0.15,apart from the peak P1,another peak P2 is observed at 200 K.In addition,the position of the structure phase transition revealed by shear modulus moves to lower temperature side with the Li content increasing.