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RARE METALS, SEMICONDUCTORS
Название Research of particularities in formation of microstructures, mechanic and electric properties of lithium niobate ceramics in dependence of the initial charge dispersity
DOI 10.17580/nfm.2017.01.01
Автор Palatnikov M. N., Shcherbina O. B., Masloboeva S. M., Efremov V. V.
Информация об авторе

I. V. Tananaev Institute of Chemistry and Technology of Rare Elements and Mineral Raw Material KSC RAS, Apatity, Russia:

M. N. Palatnikov, Sector Leader
O. B. Shcherbina, Senior Researcher, e-mail: shcerbina@chemy.kolasc.net.ru
S. M. Masloboeva, Assistant Professor
V. V. Efremov, Senior Researcher

Реферат

The structure, mechanic and electric properties were researched in ceramics obtained on the basis of highly disperse microcrystal single phase powders of lithium niobate. Methods of research were probe microscopy and impedance spectroscopy. The distribution of powder particles sizes was narrow. The ceramic materials properties was shown to depend on dispersity of the initial powder lithium niobate charge. At this, due to formation of gradient mezostructure in LN ceramic obtained from initial charge with low specific surface area microhardness measured on the surface of this sample was almost equal to the one of samples more homogeneous in size grains and more dense synthesized from charge with higher specific surface area. At the same time Young modulus that is a strength index of the material, is naturally higher for LN ceramic samples obtained from charge with higher specific surface area. Great differences in ceramic structure on mezo- and microlevels manifest in mechanical properties especially in the destruction processes and strength. The criterion for evaluation of plastic and brittle properties was chosen micro-brittleness and brittle microstrength. The obtained data allowed us to evaluate critical stress intensity factor of the first kind KIC which is a material crack-resistance criterion. Crack-resistance and microhardness of the materials were shown to increase with increase in the dispersity of the initial charge. The dispersity of complex impedance Z*(ω) was researches for the most dense LN ceramic sample in the temperature range up to ~800 К. Real and imaginary components of the complex dielectric permittivity and complex impedance (admittance) were detected due to measured real value of impedance (Z) and phase difference angle (φ). Temperature dependence of static conductivity σsv(Т) of LN ceramic agrees with the Arrhenius law only in hightemperature area. The dependence has a monotonous shape with activation enthalpy На≈0.88 eV. Such value is typical for the ion conductivity along the ceramic grain boarders. Comparison of the specific static conductivity of ceramic and crystals LN samples revealed that ceramic conductivity is four times of magnitude higher σsv~5.0·10–8 S/m and 5.0·10–12 S/m, correspondingly.

Ключевые слова Lithium niobate, dispersity, ceramics, microhardness, Yong modulus, mechanical and electrophysical properties
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