Essentially single-phase samples of Pb2CuSr2[Eu1-xCax]Cu 2O8+δ have been investigated in a compositional range of x = 0.0-0.3. Annealing characteristics in oxygen and nitrogen atmospheres were systematically monitored by thermogravimetric measurements. Activation energies were determined for both the oxygen uptake and loss processes. The effect of Ca doping on the critical temperature was studied, and the Tc was found to be quite independent of the Ca content. The highest value of Tc = 74 K was measured for the sample of x = 0.25. The hyperfine parameters of the Eu site were determined by 151Eu Mössbauer spectroscopy. The asymmetry parameter η of the electric field gradient showed a clear dependence on both x and δ.
- Mössbauer spectroscopy
- Substitution effects