G.P. Vassilev

Studies of the phase equilibria in the Ag-Sn-Zn system

Abstract The isothermal section of the equilibrium phase diagram Ag–Sn–Zn has been constructed at 380°C using optical and scanning electron microscopy, X-ray analyses, microhardness measurements and differential scanning calorimetry. The ternary β phase (solid solution range of the binary AgZn β phase) contains up to ≈13 at.% Sn, the ϵ phase about 0.2 at.% Sn. The solubility of Zn in the Ag–Sn-based intermetallic phases is determined for the first time. The microhardness of the γ phase (≈450 MPa) is the highest in the system Ag–Sn–Zn. A linear dependence of the microhardness versus mol fraction of silver has been revealed for the ϵ phase.

Experimental study of the ternary Ag–Sn–Zn system through diffusion couples

Abstract The phase boundaries of the ternary Ag–Sn–Zn system have been verified using diffusion couples. Concentration and microhardness profiles of the diffusion zone have been constructed. Solid state precipitations at room temperature have been observed in the binary AgSn F.C.C. solutions as well as in the ternary intermediate compounds. The tin solubility in the silver is less than expected according to the pertinent binary phase diagram. Growth coefficients of the intermediate phase layers (for the ternary β, γ, ϵ phases) have been assessed.

Phase equilibria in the Sn―Zn―Ni system

Abstract The objective of this study is to elucidate the phase equilibria of the Sn–Zn–Ni system. For this purpose, ternary alloys were synthesized using quartz ampoules and annealing. The samples were characterized using differential scanning calorimetry, X-ray diffraction, optical and scanning electron microscopy and microhardness measurements. The results show relatively significant solubility of tin or zinc (about 10 at.% roughly) in Ni–Zn and Ni–Sn phases, respectively. Moreover, evidence of the presence of two formerly unknown ternary compounds denoted as T1 and T2 was found. The first one has a composition (mole fraction) of about: XSn = 0.38 ± 0.04, XNi = 0.36 ± 0.02, XZn = 0.26 ± 0.03 while the approximate composition of the second is XSn = 0.26 ± 0.03, XNi = 0.55 ± 0.00, XZn = 0.19 ± 0.03. Three unidentified compositions were observed: U1 (XSn = 0.26 ± 0.07, XNi = 0.29 ± 0.03, XZn = 0.45 ± 0.04), U2 (XSn = 0.55 ± 0.01, XNi = 0.21 ± 0.00, XZn = 0.24 ± 0.01), and U3 (XSn = 0.48 ± 0.05, XNi = 0.08 ± 0.00, XZn = 0.44 ± 0.05) but there was still a lack of evidence to categorize any of them as a ternary compound. A tentative isothermal section of the Sn–Zn–Ni phase diagram at 600 °C was constructed.

Phase diagram studies of the Ti-Bi-Sn system at 400 ◦ C

Abstract The phase equilibria in the Ti–Bi–Sn system have been studied at 400xa0°C using optical and scanning electron microscopy. The homogeneity ranges and the ternary extensions of the relevant binary compounds were determined. The highest contents of the correspondent ternary element (8.2 at.% Sn and 9.0 at.% Bi, respectively) are found in Ti 2 Bi and Ti 2 Sn. A new formerly unknown ternary compound, having the approximate formula Ti 3 BiSn, has been found. An isothermal ternary phase diagram section at 400xa0°C has been constructed.

Defects in Sb2−xBixTe3 foils

Abstract Sb 2−x Bi x Te 3 foils prepared by rapidly quenching from melt have been studied using positron annihilation spectroscopy, scanning electron microscope, electron microprobe analysis and X-ray diffraction. All studied foils are crystalline and textured with preferential orientation (205) or (110). The positron annihilation data show that the foils contain monovacancy type defects. The incorporation of Bi atoms into the Sb 2 Te 3 lattice leads to the decrease of the monovacancy concentration but the type of defects is the same in all samples.

Growth kinetics of CoZn intermediate phase layers

Abstract Growth kinetics of γ2, γ1, and γ phases have been studied using metallographic, microhardness, X-ray diffraction, and X-ray microprobe methods. Activation energies of phase growth and the relevant growth constants and chemical diffusion coefficients have been determined. The following expressions describe the growth kinetics of those phases: y 2 ⋎ =3×10 −9 t exp[(−41000±1000)/RT] y 2 ⋎ =8×10 −8 t exp[(−66 000±6000)/RT] y 2 ⋎ =4×10 −7 (t−t 0 ) exp[(−100 000±3000)/RT] Here t (s) is the time since the beginning of the phase growth, to the incubation period, R (J mol−1 K−1) the universal gas constant, T the absolute temperature, and y φ (m) the thickness of the pertinent phase layer φ.

Magnetron Sputtered CuInSe2 Layers as Materials for Solid-State Batteries

As it is well known, Lithium intercalated InSe and related compounds are widely used as material for solid state batteries [1]. Such a material is CuInSe2, i.e., used in a heterojunction solid state solar cells [2]. To deposit composite thin films by DC magnetron sputtering are generally used: reactive magnetron sputtering in Ar+H2Se gas mixture [3–4] or hybrid sputtering [4].