Crystal structure, thermal and electrotransport properties of NdBa1–xSrxFeCo0.5Cu0.5O5+δ (0.02 ≤ x ≤ 0.20) solid solutions

Abstract

Using solid-state reactions method, the solid solutions of layered oxygen-deficient perovskites NdBa1–xSrxFeCo0.5Cu0.5O5+δ (0.02 ≤ x ≤ 0.20) were prepared; their crystal structure, thermal stability, thermal expansion, electrical conductivity and thermopower were studied. It was found that NdBa1–xSrxFeCo0.5Cu0.5O5+δ phases crystallize in tetragonal syngony (space group P4/mmm) and are p-type semiconductors, whose conductivity character at high temperatures changed to the metallic one due to evolution from the samples of so-called weakly-bonded oxygen. Partial substitution of barium by strontium in NdBaFeCo0.5Cu0.5O5+δ leads to the small decreasing of unit cell parameters, thermal stability and thermopower of NdBa1–xSrxFeCo0.5Cu0.5O5+δ solid solutions, increasing of their electrical conductivity values and slightly affects their linear thermal expansion coefficient and activation energy of electrical transport values.

Keywords

• layered perovskites
• thermal stability
• thermal expansion
• electrical conductivity
• thermo-emf