Crystal structure and oxygen nonstoichiometry of the third-order Ruddlesden-Popper phase Pr4(Ni0.9Co0.1)3O10-δ

• Main Authors: Christian Berger, Edith Bucher, Rotraut Merkle, Joachim Maier, Werner Sitte
• Format: Article
• Language: English
• Published: Elsevier 2021-06-01
• Series: Open Ceramics
• Subjects: Praseodymium nickelate; Third-order Ruddlesden-Popper phase; Crystal structure; Defect chemistry; Solid oxide fuel cell cathode; Solid oxide electrolyser cell anode
• Online Access: http://www.sciencedirect.com/science/article/pii/S2666539521000407

Crystal structure and thermal expansion of the third-order Ruddlesden-Popper phase Pr4Ni2.7Co0.3O10-δ (PNCO) were determined by high temperature X-ray powder diffraction (HT-XRD) and Rietveld analysis in the temperature range 25–600 ​°C in air. The thermal expansion coefficient (TEC) of PNCO is smaller compared with first-order Ruddlesden-Popper phases and in excellent agreement with values of common electrolytes of solid oxide cells. HT-XRD, thermogravimetry, and differential scanning calorimetry showed a reversible phase transition at 600–650 ​°C. A single monoclinic (P21/a) phase occurs at 25–600 ​°C, while a mixture of monoclinic and tetragonal (I4/mmm) phases is found at 650–900 ​°C. The oxygen nonstoichiometry was determined by thermogravimetry as a function of temperature (300 ​≤ ​T/°C ​≤ ​900) and oxygen partial pressure (8.3 ​× ​10−4 ​≤ ​pO2/bar ​≤ ​8.3 ​× ​10−1). Data of the oxygen nonstoichiometry were further evaluated with respect to the partial molar enthalpy and entropy of oxygen, and the thermodynamic factor of oxygen.