With multiple elements mixed at equal or near-equal molar ratios, the emerging, high-entropy alloys (HEAs), also named multi-principal elements alloys (MEAs), have posed tremendous challenges to materials scientists and physicists, e.g., how to predict high-entropy phase formation and design alloys. In this paper, we propose some guidelines in predicting phase formation, using thermodynamic and topological parameters of the constituent elements. This guideline together with the existing ones will pave the way toward the composition design of MEAs and HEAs, as well as property optimization based on the composition–structure–property relationship.

Nanostructuring is one of the effective approaches to lower the thermal conductivity of thermoelectric materials for improving its figure of merit. The nano-sized uniform skutterudite Co1−xNixSb3 (x = 0, 0.05, 0.075, 0.125, 0.15, and 0.25) thermoelectric powders were synthesized in triethylene glycol solution by using CoCl2, NiCl2, and SbCl3 as precursors and NaBH4 as the reductant. Different synthesis conditions were studied to pursue pure and uniform skutterudite CoSb3 powders. The powders were characterized by X-ray diffraction, field emission scanning electron microscope, and energy-dispersive X-ray analysis. Experimental results show that a Ni-doped skutterudite Co1−xNixSb3 single phase was obtained at 290 °C for 12 h. The powders are spherical, small, and uniform. As x increases from 0 to 0.25, the unit-cell parameter a increases from 0.9044 to 0.9065 nm and the particle size increases from 10 to 30 nm.

The interfacial magnetoelectric (ME) effect in ferromagnetic-ferroelectric (FM-FE) tunneling junctions was investigated in this work. We found that the tunneling magnetoresistance (TMR) changes with the reversing of the electric polarization of the FE barrier. The theoretical results also indicated that TMR is strongly dependent on the electric polarization, the exchange splitting energy, the screening lengths in the electrodes, and the dielectric constant of the FE barrier layer. These results may provide some insights into switching magnetization electrically for spintronics and presenting independent tunneling states in a single junction for multi-value storage memory applications.

MgxZn1−xO films were grown on quartz substrates at 773 K by using radio frequency magnetron sputtering with a mixture of argon and nitrogen as sputtering gases. The nitrogen concentration in the mixture is characterized by the nitrogen partial pressure ratio, which is determined by the ratio of nitrogen flow rate to the flow rates of nitrogen and argon. It was found that Mg concentration, structure, and band gap of the MgxZn1−xO film could be tuned by changing the nitrogen partial pressure ratio of the sputtering gases. The Mg concentration in the MgxZn1−xO film increases with increasing nitrogen partial pressure ratio. The MgxZn1−xO film consists of wurtzite phase at the ratios from 0% to 50%, mixture of wurtzite and cubic phases at the ratios between 50% and 83%, and cubic phase at 100%. The band gap of the MgxZn1−xO film with wurtzite and cubic structure increases as the ratio rises. The variation of the structure and band gap is attributed to change of the Mg concentration, which results from loss of the O and Zn atoms during growth process, the former is induced by reaction between N and O, and the latter by re-evaporation of Zn atoms due to high substrate temperature. The mechanism of the loss of the O and Zn atoms is discussed based on thermodynamics.

A wurtzite nitrogen-doped MgZnO (MgZnO:N) film was grown by plasma-assisted molecular-beam epitaxy (PAMBE) on c-plane sapphire using radical NO as oxygen source and nitrogen dopant. The as-grown film shows n-type conduction at room temperature, but transforms into p-type conduction after annealed. Photoluminescence (PL) spectrum measured at 80 K is dominated by neutral donor-bound exciton emission (D0X) located at 3.522 eV for the n-type MgZnO:N film, but by neutral acceptor-bound exciton emission (A0X) located at 3.515 eV for the p-type MgZnO:N film. By fitting exciton emission intensity of temperature-dependent PL spectra, the binding energies of the D0X and A0X were estimated to be 32 and 43 meV, respectively. Based on the energy shift of exciton emission, the band gap of the MgZnO:N film is estimated to be 3.613 eV, which is 179 meV larger than that of ZnO. Using the Haynes rule, the acceptor energy level of the MgZnO:N film was evaluated to be about 176 meV above the valence band.

Two isothermal sections of the Co–Cu–Ti ternary system at 973 and 1123 K were experimentally determined using the diffusion triple technique together with scanning electron microscopy and electron probe microanalysis. The solubility of Cu (substituting Co) in CoTi increased from 22.8 at.% at 973 K to 28.1 at.% at 1123 K while that of Co (substituting Cu) in CuTi decreased from 11.1 to 8.8 at.% accordingly. In addition, the solubility limits of the third element in the binary compounds CoTi2, CuTi2, Cu4Ti3, and Cu3Ti2 were remarkable. Besides the solubility change, we found the Cu2Ti phase was stable at 1123 K but disappeared at 973 K. A ternary compound “m” with a composition range covering Co10Cu57Ti33 was detected at both isothermal sections. An invariant reaction Cu4Ti3 + CoTi ↔ CuTi + m at a temperature between 973 and 1023 K was deduced. Further investigations are necessary to confirm the reactions among Cu, Cu4Ti, Cu2Ti, Cu3Ti2, and “m” between 1023 and 1123 K.

Sm(Co,Cu,Fe,Zr)z 2:17 based permanent magnets have the highest Curie temperature and the most excellent temperature stability among the current rare-earth permanent magnets. in recent years, the Sm(Co,Cu,Fe,Zr)z magnets have attracted again considerable attention due to the demand of the Department of Defense for high temperature applications such as aircraft, spacecraft and ship systems. Our recent studies have led to the development of new precipitation hardened Sm(Co,Fe,Cu,Zr)z magnets with operating temperatures above 400°C and with coercivities as high as 10 kOe at 500°C. The microstructure of the Sm(Co,Cu,Fe,Zr)z high temperature magnets consists of a cellular structure (2:17 rhomobohedral cells surrounded by 1:5 hexagonal cell walls) superimposed on a lamella phase (2:17 hexagonal). This microstructure is sensitive to processing and to the alloy chemical composition. Magnetic domain structure studies play a critical role in understanding the magnetic hardening behavior of the magnets. in this paper, HREM and magnetic domain structure were studied in these Sm(Co,Cu,Fe,Zr) high temperature permanent magnets.

The InyGa1−yAs/GaAs superlattice on InxGa1−x.As (x<y) buffer layer was grown by MOCVD. The well layer is under compressive strain and the barrier layer is under tensile strain. However, both layers do not exceed the calculated critical value based on the M−yAs interface was smoother than the InyGa1−yAs/GaAs interface; the Indium composition gradual region at the GaAs/InyGal1−yAs interface was narrower than that at the InyGa 1−yAs/GaAs interface; in InyGa1−yAs alloy layer, the Indium composition near the GaAs/InyGa1-yAs interface was higher than that near another interface. For the first time, we explained the composition profile in this kind of superlattice based on the indium segregation theory. A new strain relaxation model, in which the 30-degree and 90-degree shockley partial dislocations were taken into account under both tensile and compressive strains, was presented to explain the difference of the smoothness between the GaAs/InyGa1−yAs interface and the InyGa 1−yAs/GaAs interface.

We have performed photoluminescence (PL) measurements at liquid nitrogen temperature under high pressure up to 5.5 GPa and in the temperature range 10-300 K at atmospheric pressure on {(ZnSe)30(ZnSe0.92Te0.08)30(ZnSe)30[(CdSe)1(ZnSe)2]9}x5 multiple quantum wells. The PL peaks, EB, E1 and Ew corresponding to the band edge luminescence in ZnSe barrier layer, the transitions from the first conduction subband to the heavy-hole subband in ZnSe0.92Te0.08 layers and [(CdSe)1(ZnSe)2]9 ultra short period superlattice quantum well (SPSLQW) layers have been observed. Experimental results show that ZnSe0.92Te0.08/ZnSe forms a type-I superlattice (SL) in contrast to the type-II ZnSe/ZnTe SL. The pressure coefficients of the EB, E1 and Ew exciton peaks have been determined as 67, 63 and 56 meV/GPa, respectively. With increasing temperature (or pressure), the E1 peak-intensity drastically decreases which is attributed to the thermal effect (or the appearance of many defects in ZnSe0.92Te0.08 under higher pressure).