No abstract

The structural, magnetic electrical and thermoelectric properties of heavy rare-earth ternary compounds RNiSb were investigated. Except Yb--based compound (and nonmagnetic Lu), all compounds are low temperature antiferromagnets. YbΝi0.9 Sb reflects some mixed valence behaviour. Magnitude of the resistivity indicates tlat investigated compounds are semimetals or high doped semiconductors.

The Pechini sol-gel method was applied to obtain LiMn 2 − x T x O 4 (T = Ni, Fe; x = 0.1 to 0.5) nanopowders. Crystal and electronic structures, chemical composition and magnetic properties of the materials were characterized by X-ray diffraction, XPS, SEM/EDX microscopy, prompt gamma-ray activation analysis (PGAA), Mössbauer spectroscopy and magnetic susceptibility, respectively. XRD measurements showed that the LiMn 2 − x Ni x O 4 were single phase for x = 0.1 and 0.2. Three samples with higher Ni content contained some addition of a second phase. Analysis of the oxidation state of the dopants by XPS revealed ionic Ni 2+ and Fe 3+ . Mössbauer spectroscopy also confirmed 3+ oxidation state of iron and its location in octahedral sites, which excluded the inverse spinel configuration. XPS examinations showed that Mn 3+ ions dominated in the iron substituted series whereas the Mn 4+ was dominant in the nickel series.