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

Abstract

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.

Keywords

• Praseodymium nickelate
• Third-order Ruddlesden-Popper phase
• Crystal structure
• Defect chemistry
• Solid oxide fuel cell cathode
• Solid oxide electrolyser cell anode