Effect of Partial Lanthanide Substitutions of Gd123 Submicronic Powder

$\mathbf{GdLn}_{\mathbf{x}}\mathbf{Ba}_{2-\mathbf{x}}\mathbf{Cu}_{3}\mathbf{O}_{\mathbf{y}} (\mathbf{Ln}=\mathbf{La}, 0\leq \boldsymbol{x}\leq 0.6;\mathbf{Ln}=\mathbf{Nd}, \mathbf{Sm, Eu}, 0\leq \boldsymbol{x}\leq 0.5)$ (Gd123:Ln) samples were synthesized using the sol-gel method. The homogeneity region, variation of the crystal lattice and oxygen stoichiometry of the Gd123:Ln solid solutions were studied as a function of the substitution degree $\boldsymbol{x}$. It was shown that the homogeneity region becomes wider when going from Eu³⁺ $(\boldsymbol{x}\leq 0.35)$ to La³+ $(\boldsymbol{x}\leq 0.5)$, but for all lanthanides the symmetry changes from orthorhombic to tetragonal for $\boldsymbol{x}\sim 0.05$. Measurements of the electrical resistance of Gd123:Ln samples in the temperature range 77–300 K revealed superconducting transition temperatures over 77 K only for $\boldsymbol{x}=0$ and $\boldsymbol{x}=0.05$.