Reichmann Thomas L, Ganesan Rajesh, Ipser Herbert
Department of Inorganic Chemistry (Materials Chemistry), University of Vienna, 1090 Vienna, Austria.
Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu, India.
J Alloys Compd. 2014 Oct 15;610(100):676-683. doi: 10.1016/j.jallcom.2014.05.062.
Vapour pressure measurements were performed in terms of a non-isothermal isopiestic method to determine vapour pressures of Cd in the system Cd-Gd between 693 and 1045 K. From these results thermodynamic activities of Cd were derived as a function of temperature for the composition range 52-86 at.% Cd. By employing an adapted Gibbs-Helmholtz equation, partial molar enthalpies of mixing of Cd were obtained for the corresponding composition range, which were used to convert the activity values of Cd to a common average sample temperature of 773 K. The relatively large variation of the activity across the homogeneity ranges of the phases CdGd and CdGd indicates that they probably belong to the most stable intermetallic compounds in this system. An activity value of Gd for the two phase field CdGd+L was available from literature and served as an integration constant for a Gibbs-Duhem integration. Integral Gibbs energies are presented between 51 and 100 at.% Cd at 773 K, referred to Cd(l) and α-Gd(s) as standard states. Gibbs energies of formation for the exact stoichiometric compositions of the phases CdGd, CdGd, CdGd and CdGd were obtained at 773 K as about -19.9, -21.1, -24.8, and -30.0 kJ g atom-, respectively.
采用非等温热重法进行蒸气压测量，以确定Cd-Gd体系中Cd在693至1045K之间的蒸气压。根据这些结果，得出了Cd的热力学活度随温度的变化关系，其组成范围为52-86原子百分比Cd。通过采用修正的吉布斯-亥姆霍兹方程，得到了相应组成范围内Cd的混合偏摩尔焓，并用于将Cd的活度值转换为773K的共同平均样品温度。在CdGd和CdGd相的均匀范围内，活度的相对较大变化表明它们可能是该体系中最稳定的金属间化合物。文献中给出了两相区CdGd+L中Gd的活度值，并用作吉布斯-杜亥姆积分的积分常数。给出了773K下51至100原子百分比Cd之间的积分吉布斯自由能，以Cd(l)和α-Gd(s)作为标准态。在773K时，CdGd、CdGd、CdGd和CdGd相精确化学计量组成的生成吉布斯自由能分别约为-19.9、-21.1、-24.8和-30.0kJ·g原子-1。
