Crystal Structure, Raman Spectra and Electrical Conductivity of LiNb1 – xTaxO3 Nanopowders Obtained with High-energy Ball Milling

Authors O. Buryy1, L. Vasylechko1, V. Sydorchuk2, A. Lakhnik3, Yu. Suhak4, D. Wlodarczyk5, S. Hurskyj1, U. Yakhnevych1, Ya. Zhydachevskyy1,5, D. Sugak1,6, A. Suchocki5,7, H. Fritze4

1Lviv Polytechnic National University, 12 Bandera St., 79013 Lviv, Ukraine

2Institute for Sorption and Problems of Endoecology, NASU, 13 Gen. Naumov St., 03164 Kyiv, Ukraine

3G.V. Kurdyumov Institute of Metal Physics NASU, 36 Acad. Vernadsky Blvd., 03142 Kyiv, Ukraine

4Institute for Energy Research and Physical Technologies, Clausthal University of Technology, 19B Am Stollen, 38640 Goslar, Germany

5Institute of Physics PAS, 32/46 Al. Lotnikow, 02668 Warsaw, Poland

6Scientific Research Company ‘Electron-Carat’, 202 Stryjska St., 79031 Lviv, Ukraine

7Institute of Physics, University of Bydgoszcz, 11 Weyssenhoffa St., 85064 Bydgoszcz, Poland

Issue Volume 13, Year 2021, Number 2
Dates Received 15 February 2021; revised manuscript received 15 April 2021; published online 21 April 2021
Citation O. Buryy, L. Vasylechko, V. Sydorchuk, et al., J. Nano- Electron. Phys. 13 No 2, 02038 (2021)
PACS Number(s) 61.05.C −, 78.30. − j, 72.20. − i
Keywords Nanoparticles (70) , Nanopowders, Lithium niobate-tantalate, X-ray diffraction (19) , Micro-Raman spectroscopy, Temperature dependence of conductivity.

The X-ray diffraction, Raman scattering, and the temperature dependences of electrical conductivity are investigated for LiNb1 – xTaxO3 nanopowders of different composition (x = 0, 0.25, 0.5, 0.75, 1) obtained by mechanochemical synthesis with the use of the planetary ball mill. All samples were thermally treated at 550 ºC; in addition, some of them were annealed at 800 ºC. The comparison of the obtained structural parameters of LiNb1 – xTaxO3 samples with the structural data for LiNbO3 and LiTaO3 points to the formation of the LiNb1 – xTaxO3 solid solution. It is revealed that an increase in Ta content in LiNb1 – xTaxO3 nanopowders leads to an increase in the a-parameter of the crystal lattice and a simultaneous decrease in the c-parameter that eventually leads to a slight decrease in the unit cell volume. The average size of crystallites varies from 31 nm for the nanopowders annealed only at 550 ºC to 206 nm for the ones additionally annealed at 800 ºC. It is shown that although the Raman spectra of the investigated nanopowders are similar, some peculiarities are also observed. They arise from the different compositions of nanopowders, as well as from the presence of LiNb(Ta)3O8, Nb2O5 and/or Ta2O5 parasitic phases. For the first time, an intense band was revealed in the Raman spectra of samples with x ≠ 0. This band is observed in the region of 1008…1009 cm – 1 and, probably, cannot be connected with the presence of parasitic phases. The temperature dependences of pressured LiNb1 – xTaxO3 nanopowders conductivity are investigated at temperatures of 400…940 ºC. The determined activation energies of the electrical conductivity (1.328 eV for x = 0.5, 1.232 eV for x = 0.75, and 1.166 eV for x = 1) are close to the known values for pure LiNbO3 and LiTaO3 in the temperature range of ionic conduction.

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