Preparation of Structural Phase Diagram of Ln2Ni1-XCuxO4+δ (Ln=La, Pr, Nd, Sm, Eu) as New Cathode Materials: Variation of Structural Phase Diagram on Kinds of Ln. (30th May 2017)

• Record Type: Journal Article
• Authors: Soga, Haruki; Wang, Chengkun; Hayashi, Tomoki; Morise, Takahiko; Niwa, Eiki; Hashimoto, Takuya
• Is Part Of: ECS transactions. Volume 78:Number 1(2017)
• Page Start: 613
• Page End: 622
• Publication Date: 2017-05-30
• Subjects: Electrochemistry -- Periodicals; Electrochemistry; Periodicals; Electronic journals; Electronic journal; 541.37
• DOI: 10.1149/07801.0613ecst
• Languages: English
• ISSNs: 1938-5862

Abstract

Abstract : Crystal structure of Ln2 Ni1- x Cu x O4+ δ (Ln= La, Pr, Nd, Sm and Eu), which are expected as new cathode materials for solid fuel cells, was investigated. Single phase with K2 NiF4 structure, so-called T-phase, was obtained for La2 Ni1- x Cu x O4+ δ regardless of Cu content. Single phase with Nd2 CuO4 structure, so-called T'-phase, was obtained for Sm2 Ni1- x Cu x O4+ δ and Eu2 Ni1- x Cu x O4+ δ for only 0.95≤ x ≤1.0 and x =1.0 respectively. No T-phase was obtained for the other composition of Ln2 Ni1- x Cu x O4+ δ (Ln=Sm, Eu). The single T-phase and T'-phase were obtained for Pr2 Ni1- x Cu x O4+ δ with x ≤0.4 and x =1.0, respectively. For Pr2 Ni1- x Cu x O4+ δ with x between 0.5 and 0.9, phase separation into T-phase and T'-phase due to miscibility gap was observed, showing similar behavior with Nd2 Ni1- x Cu x O4+ δ except for little smaller x range of the miscibility gap. From high temperature X-ray diffraction measurements, it was revealed that the miscibility gap between 0.5 and 0.9 of Pr2 Ni1- x Cu x O4+ δ remained up to 700 °C. Variation of the crystal structure of Ln2 Ni1- x Cu x O4+ δ on kinds of Ln and Cu content could be explained by using tolerance factor calculated from ionic radius of Ln 3+, Ni 2+ and Cu 2+ .