14 research outputs found
First-principle solubilities of alkali and alkaline earth metals in Mg-B alloys
By devising a novel framework, we present a comprehensive theoretical study
of solubilities of alkali (Li, Na, K, Rb, Cs) and alkaline earth (Be, Ca, Sr,
Ba) metals in the he boron-rich Mg-B system. The study is based on
first-principle calculations of solutes formation energies in MgB, MgB,
MgB alloys and subsequent statistical-thermodynamical evaluation of
solubilities. The advantage of the approach consists in considering all the
known phase boundaries in the ternary phase diagram. Substitutional Na, Ca, and
Li demonstrate the largest solubilities, and Na has the highest (0.5-1 % in
MgB at K). All the considered interstitials have negligible
solubilities. The solubility of Be in MgB can not be determined because the
corresponding low-solubility formation energy is negative indicating the
existence of an unknown ternary ground state. We have performed a
high-throughput search of ground states in binary Mg-B, Mg-, and B-
systems, and we construct the ternary phase diagrams of Mg-B- alloys based
on the stable binary phases. Despite its high temperature observations, we find
that SrMg is not a low-temperature equilibrium structure. We also
determine two new possible ground states CaB and RbB, not yet
observed experimentally.Comment: 5 figure
Synthesis, Crystal Structure Refinement, and Electrical Conductivity of Pb(8−x)Na2Smx(VO4)6O(x/2)
Solid solutions of Pb(8−x)Na2Smx(VO4)6O(x/2) were studied using X-ray diffraction analysis including Rietveld refinement and scanning electron microscopy and by measuring their electrical conductivity. Crystal structure of the solid solutions was refined and the solubility region 0 ≤ x ≤ 0.2 was determined for samarium substitution for lead under the scheme 2Pb2+ + ◻ → 2Sm3+ + O2-. The influence of degree of substitution on the electrical conductivity of solid solutions was established