La and Sr Substituted Pr2NiO4+δ: Oxygenation and Electrical Properties

✍ Scribed by C. Allançon; P. Odier; J.M. Bassat; J.P. Loup

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 290 KB
• Volume: 131
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1997.7402

✦ Synopsis

We report herein results concerning the solid solutions Pr 2؊x M x NiO 4؉ , M ‫؍‬ La, Sr. These two cations are larger than praseodymium and lead to a structural stabilization. The oxygen excess decreases with x for La and Sr substituted Pr 2 NiO 4؉ . Both cases suggest that structural strain is a leading factor for the oxygenation ability of the title compounds. From the evolution of cell parameters, we suggest a phase transition for La substituted compounds occurring for x&1-1.2. Surprisingly, this transition has a negligible effect on transport properties. On the other hand, a charge localization linked to the presence of praseodymium is observed. Owing to charge compensation, the Sr substituted compounds have a quasi-constant hole concentration (formally 50%) for x(0.5. The Pr 2؊x Sr x NiO 4؉ solid solution shows an anomalous behavior for x ‫؍‬ 0.5 corresponding to Ni 2؉ /Ni 3؉ ‫؍‬ 1. This anomaly combines an enhancement of the c/a ratio, a larger resistivity, and a peak for the activation energy of the resistivity versus T.