La_(2-x)Nd_xCuO_(4+δ)(0.1≤x≤1.2)体系中滞弹性弛豫与相变内耗研究

Anelastic relaxation and phase transition internal friction properties of La_(2-x) Nd_x CuO_(4 +δ) (0. 1≤x≤1. 2) compounds

通过对La2-xNdxCuO4+δ(0.1≤x≤1.2)体系中滞弹性弛豫与相变内耗性能的研究发现,当0.1≤x≤1.0时,在250K左右存在一个与间隙氧有关的弛豫内耗峰,并且当0.1≤x≤0.4时,弛豫内耗峰峰高随着x值的增大而升高,此时体系为正交结构;当0.5≤x≤1.0时,体系在宏观上呈现四方结构,此时内耗峰峰高随着x值的增大而降低,当x继续增大到1.2时,内耗峰完全消失.此外,在0.1≤x≤0.8区间,高温区550K左右还存在一个相变内耗峰,其相转变温度随着x值的增大向高温偏移,相应温区的弹性模量有异常变化.分析表明,此相变峰对应着体系中的正交—四方相的转变.

The low-frequency internal frictions of La2-xNdxCuO4 ＋ δ（0.1≤x≤1.2） compounds are measured.The results show that the relaxation internal friction peak related to the excess oxygen atoms appears around 250K with 0.1≤x≤1.0.And the peak becomes higher with the value of x increasing for 0.1 ≤ x ≤0.4 and all these compounds have orthorhombic structures.When 0.5≤x≤1.0,the compounds have all tetragonal structures on a macro scale and the peak reduces as the value of x increases.However,the sample with x = 1.2 exhibits tetragonal structure but the relaxation internal friction peak is not found.Further more,when 0.1≤x≤0.8,there exists a phase transition internal friction peak around 550K.The transition temperature shifts toward high temperature zone as the value of x increases and relative shear modulus M is enlarged.But for x = 1.0 and 1.2,there appears no phase transition internal friction peak in the measurement range.We find that all these phase transition internal friction peaks are related to the transition between the orthorhombic structure and the tetragonal structure.