Energetics of T, T′, and T* Phases in Some Rare Earth Cuprates
Energetics of T, T′, and T* Phases in Some Rare Earth Cuprates
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一些稀土铜酸盐中 T、T′ 和 T* 相的能量
DOI：
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发表时间：
1993
期刊：
影响因子：
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通讯作者：
T. Shaw
中科院分区：
文献类型：
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作者：
K. Mocała;A. Navrotsky;J. Bringley;B. A. Scott;M. Frisch;T. Shaw
测量了Nd_2CuO_4（T′），（La_（1-x）Nd_x）_2CuO_4（T或T′），（La0.60Dy0.35Ce0.05）_2CuO_4（T′和T*）和（La0.60Dy0.35Th0.05）_2CuO_4（T ′-和T*）在704°C熔融2 PbO·B_2O_3中的溶解度。（La 1-x Ndx）2CuO 4（0 ≤ x ≤ 1）在700°C下的生成焓（来自氧化物）在-20至-7 kJ mol-1之间变化，取决于组成。（La0.75Nd0.25）2CuO 4的T′ → T转变焓为+6.3 ± 2.8kJmol-1。从T′到T的跃迁的外推能谱为：La 2CuO 4为+3 ± 8 kJ mol-1，Nd 2CuO 4为+28 ± 10 kJ mol-1。（La 1-x Ndx）2 CuO 4的T′相混合焓为正，规则焓相互作用参数为+51.8 kJ mol-1.正的混合焓反对阳离子有序在这个系统中是重要的。（La0.6Dy0.35Th0.05）_2CuO_4和（La0.6Dy0.35Ce0.05）_2CuO_4的T ~* 到T′的跃迁能量分别为+38 ± 5和+51 ± 6 kJ mol ~（-1）。T′和T（或T* 和T′）相之间的转变焓（ΔH）与转变体积（ΔV）呈线性关系，ΔH（kJ mol-1）= 37.4 + 9.27 ΔV（cm ~ 3 mol-1）。
Abstract The enthalpies of solution in molten 2PbO · B2O3 at 704°C of Nd2CuO4 (T′), (La1-x Ndx)2CuO4 (T or T′), (La0.60Dy0.35Ce0.05)2CuO4 (T′ and T*), and (La0.60Dy0.35Th0.05)2CuO4 (T′- and T*) have been measured. The enthalpy of formation (from oxides) at 700°C of (La1-x Ndx)2CuO4 (0 ≤ x ≤ 1) varies from -20 to -7 kJ mol-1, depending on composition. The enthalpy of the T′ to T transition in (La0.75 Nd0.25)2CuO4 is +6.3 ± 2.8 kJ mol-1. Extrapolated enthalpies of transition from T′ to T are +3 ± 8 kJ mol-1 for La2CuO4 and +28 ± 10 kJ mol-1 for Nd2CuO4. The enthalpy of mixing in the T′ phase of (La1-x Ndx)2 CuO4 is positive, with a regular enthalpy interaction parameter of + 51.8 kJ mol-1. The positive enthalpy of mixing argues against cation ordering being important in this system. The enthalpies of transition of T* to T′ of (La0.6Dy0.35Th0.05)2CuO4 and (La0.6Dy0.35Ce0.05)2CuO4 are +38 ± 5 and +51 ± 6 kJ mol-1, respectively. There is a linear dependence of the enthalpy of transition (ΔH) between T′ and T (or T* and T′) phases on the volume of transition (ΔV), ΔH (kJ mol-1) = 37.4 + 9.27 ΔV (cm3 mol-1).