Electronic properties of Pr4Ni3O10±δ

Two synthesis methods for preparing Pr₄Ni₃O_10±δ are compared : a modified sol — gel route and a nitrate — citrate one. It is shown that the autoignition involved in the nitrate — citrate route provides good conditions ressembling the Rapid Thermal Annealing procedure. The oxygen stoichiometry of Pr₄Ni₃O_10±δ phases is measured according to the method of synthesis and thermal treatment. The compounds are metallic as seen by electrical resistivity measurements and thermoelectric power. We show that the adjustment of δ in this series is an important parameter of the transport properties that change from metallic for −0.1 <δ < 0.1 to insulating for Pr₄Ni₃O_8.25. An electronic anomaly is evidenced at 160 K, which intensity is more marked for the stoichiometric Pr₄Ni₃O₁₀. Our results are consistent with the existence of a charge density wave instability.