Structural and electrical properties of T′-type Ln₂CuO₄ (Ln = Pr, Nd, Sm, Eu and Gd) ceramics

T′-type Ln₂CuO₄ (Ln = Pr, Nd, Sm, Eu and Gd) were successfully synthesized in phase pure form using conventional solid state reaction and sintering route. For all the Ln₂CuO₄ samples, the solid state reaction temperature was found to be 950 °C and pure phase was realized only after 2-3 intermediate milling and solid state reaction cycles, irrespective of the lanthanide ion radius. Effect of lanthanide ion contraction on the structural properties was clearly revealed by the powder X-ray diffraction, with the XRD peaks observed to be shifting towards higher 2θ values with the decrease in Ln ionic radii. The optimum sintering temperature of these solid state reacted Ln₂CuO₄ powder was found to be 1100 °C except for Pr₂CuO₄ powder. The conductivity of these samples were tested over a wide temperature range (−100 to 150 °C), an anomaly was observed in the conductivity of all the Ln₂CuO₄ samples near the antiferromagnetic ordering temperature of Cu (~ 30 °C), thus suggesting the bearing of ordering of magnetic moments on the electrical properties.