GdBaCo_2O_(5+δ)体系的滞弹性内耗研究

Anelastic relaxation of excess oxygen in GdBaCo_2O_(5+δ)system studied by low-frequency internal friction

GdBaCo2O5+δ体系的低频内耗研究表明:体系中存在一个由额外氧运动引起的弛豫内耗峰;额外氧δ对这个弛豫内耗峰的大小、峰形及峰位有较大影响,反映了额外氧状态随δ而变化.当δ=0.005,体系中额外氧含量很少而接近零时,相应的内耗峰消失;δ达到一定数量后,出现弛豫内耗峰.由δ=0.278,0.407,0.421,0.515样品的弛豫内耗峰分析可得到体系随δ不同存在着三种不同的额外氧形态.此外,δ=0.421及0.515的样品在360K附近存在一个相变内耗峰,它对应着体系中的金属—绝缘体转变.

The investigation of GdBaCo2O5 ＋ δ system using low frequency internal friction method indicates that there exists a relaxation internal friction peak originated from the jump of excess oxygen atoms. The excess oxygen content δ affects greatly the height, shape and position of the peaks, which reflects the state of the excess oxygen varying with the value of δ When the excess oxygen content is very small, say for the sample with δ = 0. 005, the corresponding internal friction peak disappears. On increasing the excess oxygen the relaxation internal friction peak will be observed. Three different states of excess oxygen can be concluded from the relaxation peaks which exist in the samples with δ = 0.278,0.407,0.421,0.431 and 0.515. In addition, an internal friction peak with the features of phase transition are also observed in samples with δ= 0.421 and 0. 515 at about 360K, which may be attributed to metal -insulator transition.