Dresden 2017 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 22: Poster session I

MM 22.1: Poster

Montag, 20. März 2017, 19:00–20:00, P4

Nano-scale grain substructure as a factor determining transport properties of ceramic manganites — •Anastasiia Novokhatska and Gennadiy Akimov — Donetsk Institute for Physics and Engineering named after A. A. Galkin of the National Academy of Sciences of Ukraine, Av. Nauky 46, Kyiv, 03680, Ukraine

We present a new method for obtaining nano-scale grain substructure in La0.65(Ca,Sr)0.35MnO3 manganite ceramics sintered at 1500 ^∘C by means of excess manganese from 10 and 20 % as well as the study of its structure and magnetoresistive properties. With results of the scanning electron microscopy research, it is shown that the presence of excess manganese allows to sinter ceramics at temperatures of up to 1500 ^∘C while maintaining the chemical and phase composition. The ceramic samples consist of manganite grains with sizes  100 µm and Mn3O4 hausmannite grains. Moreover, investigations of thermally etched cleaved surfaces of ceramics grains together with X-ray diffraction data showed that manganite grains have internal layered structure with the layer size of 70-140 nm where each layer is a perfect single crystal of manganite of the stoichiometric composition. It is found that the emergence of a nano-scale substructure of grains is accompanied by the resistivity drop (two orders of the magnitude) and by reduction of the slope of its temperature dependence. Moreover, the metal-insulator transition temperature is shifted towards a lower temperature and the value of the magnetoresistivity (at the applied magnetic field of 5 kOe) increase in 2.5 times.