The Fluorite-Like Phase Nd5Mo3O16 +/-delta in the MoO3-Nd2O3 System: Synthesis, Crystal Structure, and Conducting Properties
Journal article, 2018

This paper describes a study of the system MoO3-Nd(2)O(3)using a combination of X-ray powder diffraction (XRD), neutron powder diffraction (NPD), thermogravimetric analysis (TGA), and ac impedance spectroscopy (IS). A phase-pure material is observed at a composition of 45.5 mol % Nd2O3, which corresponds to an ideal stoichiometry of Nd5Mo3O16.5. XRD and NPD show that the crystal structure is a superstructure of the fluorite arrangement, with long-range ordering of the two cation species leading to a doubled unit cell parameter. The sample is found to be significantly oxygen deficient, i.e. Nd5Mo3O15.63(4), when it is prepared by a solid-state reaction at 1473 K in air. TGA measurements indicate that the sample loses only minimal mass on heating to 1273 K in O-2. IS studies of the mean conductivity under different atmospheres show that the sample is a mixed conductor between ambient temperature and 873 K, with a dominant electronic component at higher temperatures, as demonstrated by measurements under inert atmosphere. NPD measurements indicate that the anion vacancies are preferentially located on the O2 sites, while studies of the temperature dependence performed under an O(2)atmosphere to 1273 K show significantly anisotropic thermal parameters of the anions. Together with analysis of the total neutron scattering data, this supports a model of oxygen ions hopping between O2 positions, with a vacancy, rather than interstitial, mechanism for the anion diffusion.

Author

Jordi Jacas Biendicho

Catalonia Inst Energy Res

Helen Y. Playford

STFC Rutherford Appleton Lab

Habibur Seikh Mohammad Rahman

Chalmers, Chemistry and Chemical Engineering

Stefan Norberg

Chalmers, Chemistry and Chemical Engineering

Sten Eriksson

Chalmers, Chemistry and Chemical Engineering, Energy and Material, Environmental Inorganic Chemistry 2

Stephen Hull

STFC Rutherford Appleton Lab

Inorganic Chemistry

0020-1669 (ISSN) 1520-510X (eISSN)

Vol. 57 12 7025-7035

Subject Categories

Inorganic Chemistry

Materials Engineering

Materials Chemistry

Driving Forces

Sustainable development

DOI

10.1021/acs.inorgchem.8b00734

PubMed

29812935

More information

Latest update

11/1/2018