Ce and Tb substitution for Y in YBa_{2}Cu_{3}O_{7} thin films

The kinetic differences of growth between standard solid-state synthesis and in situ growth by laser ablation have allowed the substitution of Ce and Tb for Y in ${\mathrm{Y}}_1$ ${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$ for the first time. The effects of Ce and Tb substitution on the material ${\mathit{T}}_{\mathit{c}}$ is discussed within the framework of the existing models for the Pr system. We suggest that localization of the holes by trapping may provide a suitable mechanism to account for the observed properties of the Pr and Ce substituted compounds.