The article "Phase Equilibria and Electrical Properties of Samples in the System Li2O–B2O3–Yb2O3" has been published in the Russian Journal of Inorganic Chemistry with impact factor 0,822 (CA)
Jun 11, 2020 | 10:02 / Important events
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The standard Gibbs energies DGf (298 K) of formation of the binary and ternary compounds (C1 and C2) were used to calculate the Gibbs free energy changes DGr in probable reactions between lithium borates and the compounds C1 and C2 in the Li2O–B2O3–Yb2O3 system. The probability of the establishment of stable phase equilibrium in the section C1–2Li2O ⋅ B2O3 (DGr (298 K) = –2316 kJ/mol) is higher than that in the section C2–Li2O ⋅ B2O3 (DGr (298 K) = –1727 kJ/mol). The dependence DGr = f(T) at 25–450°C was determined with taking into account the function Cp = f(T) for the corresponding oxides. Samples in the Li2O–B2O3–Yb2O3 system were synthesized and studied by differential thermal analysis, X-ray powder diffraction analysis, and thermodynamic analysis. Polythermal sections and an isothermal section of the phase diagram of this system were constructed. It was shown that the polythermal sections Li2O ⋅ 3B2O3–Yb2O3 ⋅ B2O3 and Li2O ⋅ B2O3–Yb2O3 ⋅ B2O3 are non-quasi-binary, and Li2O ⋅ 2B2O3–Yb2O3 ⋅ B2O3 and Li6Yb(BO3)3–YbBO3 are quasi-binary. The isothermal section in the Li2O–B2O3–Yb2O3 system at 25°C has 15 stable tie lines, which divide the system into 14 triangles of coexisting phases. The compounds 6Li2O ⋅ Yb2O3 ⋅ 3B2O3 and 3Li2O ⋅ 2Yb2O3 ⋅ 3B2O3 were synthesized, and their physicochemical properties were studied. The temperature dependences of the electrical conductivity of polycrystalline samples in the Li2O–B2O3–Yb2O3 system at direct current were investigated. The activation energies of the conduction of semiconducting samples were determined. It was observed that, with adding Yb2O3 (x = 0–0.02), the electrical conductivity of samples of the composition (1 – x)Li2O ⋅ 3B2O3–xYb2O3 ⋅ B2O3 decreases, and the activation energy increases from 0.87 to 0.94 eV.

"Phase Equilibria and Electrical Properties of Samples in the System Li2O–B2O3–Yb2O3" M. M. Asadov, N. A. Akhmedova, S. R. Mamedova, and D. B. Tagiev. Russian Journal of Inorganic Chemistry, 2020, Vol. 65, No. 7, pp. 1061–1068.

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