Electronic properties of Pr4Ni3O10±δ

Two synthesis methods for preparing Pr4Ni3O10+/-delta 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 Pr4Ni3OT10+/-delta 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 delta in this series is an important parameter of the transport properties that change from metallic for -0.1 < delta < 0.1 to insulating for PT4Ni3O8.25. 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.