The influence of doping with Ca and Mg in YBa₂Cu₃O_7-δceramic

Abstract

Abstract.We have investigated the effect of partial substitution of Ca for Y and/or Mg for Cu on structural, compositional and magnetic properties in YBa 2 Cu 3 O 7-δ polycrystalline compounds. All prepared samples were found to be single phase with small fraction of Ba-secondary phases. Substitution by more than 2% of magnesium causes an increase of spurious phases. Energy Dispersive Spectroscopy (EDS) revealed that the distribution of Ca in the sample is quite homogenous. DC susceptibility measurements show that superconducting transition temperature Tc is reduced much more by Ca than Mg. Hysteresis loops reveal that magnetic irreversibility is decreased by Ca and Mg content. The deduced critical current density Jc does not follow the same variation. Ca alone reduces Jc for x=0.1 and x=0.2. Together with Ca, Mg compensates the reduction of Jc and increasing its content near the solubility limit gives higher Jc than in the undoped sample.

Aliovalent Calcium Doping of Yttrium Oxyhydride Thin Films and Implications for Photochromism

“…Therefore, we propose that the thin films discussed here are single-phase Ca-doped Y-oxyhydrides ((Ca z Y 1– z )­H x O y ), where Ca substitutes for Y in the lattice (0–36% Ca), and the H – fraction decreases for charge neutrality. There are many examples of single-phase compounds containing both yttrium and calcium such as hydrides, , fluorides, and others. , The success of this substitution involving Ca and Y may be attributed to the similar ionic radii of these two elements (Ca 2+ = 1–1.12 Å, Y 3+ = 0.9–1.02 Å) . To this long list of single-phase Ca/Y compounds, we suggest to add Ca-doped Y-oxyhydrides for which we find that a stable thin film can be synthesized for a Ca content of at least 0–36%.…”

“…There are many examples of single-phase compounds containing both yttrium and calcium such as hydrides, 38,40 fluorides, 41 and others. 42,43 The success of this substitution involving Ca and Y may be attributed to the similar ionic radii of these two elements (Ca 2+ = 1−1.12 Å, Y 3+ = 0.9−1.02 Å). 44 To this long list of singlephase Ca/Y compounds, we suggest to add Ca-doped Yoxyhydrides for which we find that a stable thin film can be synthesized for a Ca content of at least 0−36%.…”