Stoichiometry and defect structure of 'NdMnO3'

The phase 'NdMnO3' has been synthesised and characterised by a combination of electron probe microanalysis, X-ray and neutron diffraction and H-2-reduction thermogravimetry. NdMnO3 forms, at approximate to 1400 degrees C, over the range Nd1.00(1)Mn0.95(1)O292(1) to Nd0.88(1)Mn1.00(1)O2.72(1). Oxygen contents vary in air over the range 700 to 1400 degrees C and can be varied further, either by high pressure O-2 treatment or by reduction in H-2. The structure of 'NdMnO3' is based on the GdFeO3 structure with a Jahn-Teller distortion associated with the high proportion of Mn3+ ions present. However, it also shows a very varied defect structure; depending on composition and heal treatment, vacancies can form on any one or any two of the three sublattices, Nd, Mn and O and the overall Mn oxidation state can include 2+, 3+ and 4+ contributions. Data on compositional range and defect crystal structure are presented in the form of a novel phase diagram-defect structure map.