Nanocomposites and nanomaterials

Structure, morphology and functional properties of non-stoichiometric La0.8-xNa0.2Mn1+xO3 nanopowders
Liedienov N.A.1,2, Wei Ziyu1, Mengyun Yuan1, Fesych I.V.3, Ivanov O.V.3, Bychkov K.L.3, Prokopenko V.K.2, Pashchenko A.V.1,2,4, Levchenko G.G.1,2
1 International Centre of Future Science, State Key Laboratory of Superhard Materials of Jilin University. Qianjin Str., 2699, Changchun-130012, China.
E-mail: nikita.ledenev.ssp@gmail.com
2 Phase Transitions Department, Donetsk Institute for Physics and Engineering named after O. O. Galkin, NASU. Prospect Nauki, 46, Kyiv-03028, Ukraine.
3 Taras Shevchenko National University of Kyiv. Lva Tolstoho Str., 12, Kyiv-01030, Ukraine
4 Donetsk National University of Economy and Trade named after Michael Tugan - Baranovsky. Ostrowski Str., 16, Kryvyi Rih-50005, Ukraine.

Nanopowder samples of non-stoichiometric La0.8-xNa0.2Mn1+xO3 manganites with concentration of x = 0–0.2 were prepared by sol-gel method from La(NO3)3·6H2O (99.9% metals basis), NaNO3 (ACS; ≥ 99.0%) and Mn(NO3)2·4H2O (98%) nitrates at synthesis temperature of tsynth = 850 °C (20 h) in slow heating and cooling regimes. According to X-ray diffraction data, all samples have rhombohedrally  distorted perovskite structure. The La0.8-xNa0.2Mn1+xO3 compositions with increased content of superstoichiometric manganese have miserable amount of Mn3O4 second phase < 1 vol.% for x = 0.15 and < 3 vol.% for x = 0.2. On the basis of X-ray diffraction data analysis, the average size of the coherent scattering regions D was determined by Debye-Scherrer method on the diffraction peak broadening with angle 2θ = 22.9° (hkl = 012). It was established that with increase in x the average size D decreases from 61 nm (x = 0) to 60 nm (x = 0.05), 56 nm (x = 0.1), 55 nm (x = 0.15) and 53 nm (x = 0.2). According to TEM data, nanoparticles of lanthanum-sodium manganite have spherical-like shape and the average size of nanoparticles reduces from 81 nm (x = 0) to 72 nm (x = 0.2) that is well correlated to X-ray diffraction data. According to magnetic data, all samples are in a ferromagnetic state at room temperature, show the typical behavior for an ensemble of magnetic particles being in a single domain state and have high values of magnetocaloric effect at the Curie temperature.