PROPERTIES OF THE Ln_2BaCuO_5(Ln=Nd,Sm,Dy,Ho,Tm,Yb)CUPRATES

摘要

The thermal expansion and electrical conductivity of Ln_2BaCuO_5(Ln=Nd,Sm,Dy,Ho,Tm,Yb) were measured in air at temperatures from 293 to 1073 K. All of the materials were found to exhibit semiconducting behavior. As the ionic radius of Ln~3+ decreases, the conductivity of Ln_2BaCuO_5 drops, and the activation energy of conductivity rises--from 26.4 kJ/mol for Ln=Nd to 66.4 kJ/mol for Ln-Yb. Over the entire temperature range examined, the linear thermal expansion coefficient of all the Ln_2BaCuO_5 compounds studied is independent of the nature of the rare-earth ion and falls in the range(11-13)×10~-6 K~-1.