Investigations of the Pb₂Sr₂Y_1-xEu_xCu₃O_8+δ system by ¹⁵¹Eu Mössbauer resonance and x-ray diffraction

A series of non-superconducting Pb₂Sr₂Y_1-xEU_xCu₃O _8+δ (Pb-2213) samples with x = 0, 0.25, 0.5, 0.75 and 1.00 were synthesized under a nitrogen atmosphere. Both as-synthesized and oxygen-annealed samples were studied. The phase purity, lattice parameters, and crystal structure were analysed by x-ray diffraction measurements. The behaviour of the crystallites in a magnetic field was studied by performing grain alignment experiments on some of the samples. Replacing Y with Eu increased the unit-cell volume and changed the preferred direction of the c axes in orienting experiments. The oxygen-loaded samples were tetragonal. The hyperfine interactions of the rare-earth site were monitored using ¹⁵¹Eu Mössbauer spectroscopy. The spectra obtained exhibited electric quadrupole interaction as expected. The asymmetry parameter (η) of the electric field gradient (efg) exhibited a strong dependence on x. For the as-synthesized x = 1.0 sample η was zero.