Samples of Er1-xScxNiSb (x = 0–0.10) solid solution were synthesized by an arc-melting and the effect of doping by Sc atoms on the electrokinetic and energetic characteristics of the half-Heusler ErNiSb phase was investigated. It was established that at the studied concentrations the main carriers of electricity in the Er1-xScxNiSb semiconductor are holes. It was shown that doping of p-ErNiSb compound by Sc atoms introduced by substitution of Er atoms in 4a position is accompanied by the occupation of presented vacancies in position 4a, which leads to the reduction and elimination of structural defects of acceptor nature and corresponding acceptor band. The concentration ratio of ionized acceptors and donors generated in Er1-xScxNiSb determines the position of the Fermi level and the mechanisms of electrical conduction. The investigated solid solution Er1-xScxNiSb is a promising thermoelectric material.

Summary In the DGEBA ‐ pepa ‐ CuSiF6 system (DGEBA is diglycidyl ether of bisphenol A; pepa is polyethylenepolyamine containing ethylenediamine (eda) and diethylenetriamine (deta)), a new flame retardant‐hardener for epoxy resins in the form of a chelate complex [Cu(eda)(deta)]SiF6 was synthesized and incorporated into the DGEBA to obtain a number of CuSiF6‐containing epoxy‐amine polymers with reduced combustibility and flame‐self‐extinguishment properties. The resulting samples of the DGEBA/pepa‐CuSiF6(I‐V) were characterized using FTIR spectra, combustibility, and flammability tests and the smoke formation factor measurements. The combustibility of the polymer samples were investigated using “Ceramic tube” (CT) method. Results of CT measurement reveal that maximal temperature of gaseous products of combustion for modified epoxy‐amine polymers in comparison with the unmodified epoxy appreciably goes down and weight loss lessen. The flammability of the samples was evaluated by means of UL94 BH and UL94 BV methods. The burning rate of the DGEBA/pepa‐CuSiF6(III) and DGEBA/pepa‐CuSiF6(IV) polymers containing 44 and 66 weight fractions of CuSiF6, respectively, is dramatically reduced compared to that for unmodified epoxy (these samples do not support flame propagation). The rburn. Values for the unmodified epoxy‐amine sample (DGEBA/pepa) is 25.13 mm·min−1.

Automated The results of modeling performances of the semiconductor solid solution Er1-xScxNiSb are presented, which can be a promising thermometric material for the manufacture of sensitive elements of thermoelectric and electroresistive thermocouples. Fullprof Suite software was used to model the crystallographic characteristics of the Er1-xScxNiSb thermometric material. Modeling of the electronic structure of Er1-xScxNiSb was performed by Coring-Kon-Rostocker methods in the approximation of coherent potential and local density using the exchange-correlation potential Moruzzi-Janak-Williams and Linear Muffin-Tin Orbital in the framework of DFT density functional theory. The Brillouin zone was divided into 1000 k-points, which were used to model energetic performances by calculating DOS. The width of the energy window was 22 eV and was chosen to capture all semi-core states of p-elements. Full potential (FP) was used in the representation of the linear MT orbital in the representation of plane waves. The accuracy of calculating the position of the Fermi level was εF ± 6 meV. To verify the existence of a continuous solid solution, Er1-xScxNiSb substitution, the change in the values of the period of the unit cell a (x) was calculated within the framework of the DFT density functional theory in the range x = 0–1.0. It is presented that the calculated and experimentally obtained dependences of the period of the unit cell a(x) Er1-xScxNiSb are almost parallel, which confirms the correctness of the used tools and the obtained modeling results. To research the possibility of obtaining thermometric material Er1-xScxNiSb in the form of a continuous solid solution was performed modeling of thermodynamic calculations in the approximation of harmonic oscillations of atoms in the theory of DFT density functional for a hypothetical solid solution Er1-xScxNiSb, x = 0–1.0. It is shown that the change in the values of free energy ΔG(x) (Helmholtz potential) passes through the minimum at the concentration x≈0.1 for all temperatures of possible homogenizing annealing of the samples, indicating the solubility limit of Sc atoms in the structure of the ErNiSb compound. The presence of this minimum indicates that the substitution of Er atoms for Sc atoms in the ErNiSb compound is energetically advantageous only up to the concentration of impurity atoms Sc, x≈0.1. At higher concentrations of Sc atoms, x> 0.10, stratification occurs (spinoidal phase decay). It is shown that modeling of the mixing entropy behavior S even at a hypothetical temperature T = 4000 K shows the absence of complete solubility of Sc atoms in Er1-xScxNiSb. To model the energetic and kinetic performances of the semiconductor thermometric material Er1-xScxNiSb, particularly the behavior of the Fermi level F e , bandgap width g e the distribution of the density of electronic states (DOS) and the behavior of its electrical resistance ρ(x, T) is calculated for an ordered variant of the structure in which the Er atoms in position 4a are replaced by Sc atoms. It is shown that the ErNiSb compound is a semiconductor of the electronic conductivity type, in which the Fermi level is located near the level of the conduction band C e . The modeling showed that at higher concentrations of Sc atoms, the number of generated acceptors exceeds the concentration of uncontrolled donors, and the concentration of free holes exceeds the concentration of electrons. Under these conditions, the Fermi level F e approaches, and then the level of the valence band Er1- xScxNiSb crosses: the dielectric-metal conductivity transition occurs. The experiment should change the sign of the thermo-emf coefficient α(x, T) Er1-xScxNiSb from negative to positive, and the intersection of the Fermi level F e and the valence band changes the conductivity from activating to metallic: on the dependences ln(ρ(1/T)) the activation sites disappear, and the values of resistivity ρ increase with temperature.

The effect of doping of half-Heusler phase p-LuNiSb (MgAgAs structure type) by Zr atoms on the structural, kinetic, energetic and magnetic characteristics of the semiconductor solid solution Lu1-xZrxNiSb was studied in the ranges: T = 80–400 K, x = 0–0.10. From experimental studies it has been established that doping of p-LuNiSb compound with Zr atoms simultaneously generates both structural defects of acceptor and donor nature, the concentration of which increases with increasing content of Zr atoms. It was shown that the investigated semiconductor solid solution Lu1-xZrxNiSb is a promising thermoelectric material.

The results of experimental research of perspective thermometric material Lu1-xZrxNiSbwhich can be used for the production of sensitive elements of thermoelectric and electroresistive thermometers are presented. Thermometric materials Lu1-xZrxNiSb, x=0.01–0.10, were made by fusing a charge of components in an electric arc furnace with a tungsten electrode (cathode) in an atmosphere of purified argon under a pressure of 0.1 kPa on a copper water-cooled hearth (anode). Heat treatment of alloys consisted of homogenizing annealing at a temperature of 1073 K. Annealing of samples was carried out for 720 h in vacuumed up to 1.0 Pa ampoules of quartz glass in muffle electric furnaces with temperature control with an accuracy of ±10 K. Diffraction arrays were obtained on a diffractometer DRON-4.0 (FeKα radiation), and the structural characteristics of Lu1-xZrxNiSbwere calculated using the Fullprof program. The chemical and phase compositions of the samples were monitored using a scanning electron microscope (Tescan Vega 3 LMU). The study of the temperature dependences of the resistivity ρ(T,x) and the thermopower coefficientα(T,x) Lu1-xZrxNiSb was performed in the temperature range of 80÷400 K on samples in the form of rectangular parallelepipeds measuring ~1.0×1.0×5.0 mm3 . Measurements of the values of the specific magnetic susceptibility χ(x) of Lu1-xZrxNiSb samples were performed by the relative Faraday method at a temperature of 273 K using a thermogravimetric installation with an electronic microbalance EM-5-ZMP in magnetic fields up to 10 kGs. Microprobe analysis of the concentration of atoms on the surface of Lu1-xZrxNiSb samples, x=0.01–0.10, established their correspondence to the initial compositions of the charge, and X-ray phase analysis showed no traces of extraneous phases on the sample diffractograms, except for the main phase. The nonmonotonic nature of the change in the values of the unit cell period of the thermometric material an (x) Lu1-xZrxNiSb, x=0.01–0.10, which differs from the results of modeling structural characteristics using software packages AkaiKKR and Elk. The nonmonotonic change in the values of the period of the unit cell a(x) Lu1-xZrxNiSband the presence of the extremum dependence suggests that the impurity Zr atoms introduced into the matrix of the LuNiSb basic semiconductor can simultaneously occupy partially different crystallographic positions in different ratios. The temperature resistivities ρ and the thermopower coefficientα of the LuNiSb base semiconductor contain high- and lowtemperature activation regions, which is characteristic of doped and compensated semiconductors. The introduction into the LuNiSb structure of the lowest concentration of impurity Zr atoms in the experiment (x=0.01) radically changes both the behavior of the temperature dependences of the resistivity ρ and the thermopower coefficientα and the type of the main electric current carriers. The values of the resistivity ρ(T,x) Lu1-xZrxNiSbonly increase with increasing temperature, which is characteristic of the metallic type of electrical conductivity and is due to the mechanisms of scattering of current carriers. This nature of the change in electrical resistance ρ(T,x) is evidence that the Fermi level εF has left the bandgap εg and is in the conduction band εC. This is indicated by the negative values of thermopower coefficientα(T,x) at all concentrations and temperatures. Studies of the magnetic susceptibility χ(x) showed that the samples as a basic semiconductor LuNiSb, as well as the thermometric material Lu1-xZrxNiSb, at all concentrations of impurities Zr, are Pauli paramagnetic. There is a synchronicity of the behavior of χ(x) with the dependences of the resistivity ρ(x, T) and the thermopower coefficient α(x, T), which is due to the change in the density of states at the Fermi level g(εF). The results of experimental studies of the Lu1-xZrxNiSbthermometric material completely coincide with the results of modeling its kinetic characteristics under the presence of vacancies in the crystallographic positions 4a and 4c of the Lu and Ni atoms, respectively. Such studies allow making adjustments in the structural studies of thermometric material with an accuracy that significantly exceeds the accuracy of X-ray research methods. The obtained results will allow us to clarify the spatial arrangement of atoms in the nodes of the unit cell, as well as to identify the mechanisms of electrical conductivity to determine the conditions for the synthesis of thermosensitive materials with maximum efficiency of thermal energy conversion into electricity.