In this study, various coatings including Mo, Ti, Y2O3-stabilized ZrO2 (YSZ)/Ti films were deposited on the CoSb3 substrate using magnetron sputtering to suppress the sublimation of antimony in CoSb3 during thermal aging tests. The microstructure and growth of films were observed using scanning electron and atomic force microscopes. The thermal aging behavior of CoSb3 coated with various films was investigated through an accelerated experiment at 923 K for 24 h. The weight loss of CoSb3 decreased with the thickness of coatings increasing. Among these films, the YSZ/Ti film can suppress the sublimation of antimony in CoSb3 more effectively. Compared with the uncoated CoSb3 material, the degradation of thermoelectric properties for coated CoSb3 samples decreased slowly after the accelerated thermal aging test.

•Protective YSZ/Ti film could be deposited on the CoSb3 substrate.•The YSZ film typically grew on Ti film in the island mode.•No cracks or other defects was found in the YSZ/Ti/CoSb3 interface.•The YSZ/Ti film could effectively suppress the sublimation of Sb in CoSb3.The YSZ (yttria-stabilized zirconia)/Ti film was deposited on CoSb3 substrate by magnetron sputtering to suppress the sublimation of antimony in CoSb3 during thermal aging test. Both YSZ and Ti film were columnar crystal. The YSZ film typically grew on Ti film in the island mode. No cracks, porosity or other defects were observed on YSZ film. The weight loss per unit area of CoSb3 samples coated with YSZ/Ti film was much lower than that of uncoated CoSb3 sample after accelerated thermal aging test. The results indicated that the sublimation of antimony in CoSb3 was effectively suppressed by YSZ/Ti film.

•Discontinuous precipitation grew into the grains from grain boundaries with a lamellar growth.•Continuous precipitation formed in the remaining areas within the grains unoccupied by DP.•The interfaces between discontinuous precipitation and continuous precipitation areas were clear.Microstructure evolution of the extruded AZ80 magnesium alloy and different precipitation behavior of β-Mg17Al12 phase in different heat treatment conditions were investigated. Solution treatment caused the dissolution of β-Mg17Al12 phase and the grain coarsening. During aging, discontinuous precipitates were preferentially initiated at some of the grain boundaries and then continuous precipitates appeared in the grain interiors. In the period of direct-aging, discontinuous precipitates formed between the banded structure and no continuous precipitate appeared. After solution and aging treatment, an improved combination of strength and elongation was obtained. The highest strength was achieved for the extruded AZ80 sample after directing-aging treatment.

Ga-filled and Te-doped CoSb3 skutterudites were synthesized by a melt-quench-anneal-hot-press sintering method, and their thermoelectric properties were investigated from 300 to 800 K. The filling fraction of Ga in doped skutterudite is up to x = 0.2 and the results of XRD and lattice parameter are in agreement with the change of filling fraction. When the Ga content x = 0.3, there was the second phase GaSb existing in the skutterudite. All GaxCo4Sb11.7Te0.3 samples were the N-type conduction and the electrical conductivity increased with the content of Ga increasing. Thermal conductivity of GaxCo4Sb11.7Te0.3 decreased markedly due to the phonon scattering, which resulted from the filling of Ga atoms. The highest thermoelectric figure of merit ZT = 0.6 is achieved at 650 K in the Ga0.3Co4Sb11.7Te0.3 compound.Graphical abstractHighlights► Ga-filled and Te-doped CoSb3 skutterudites were synthesized. ► The filling fraction of Ga in GaxCo4Sb11.7Te0.3 skutterudite is up to x = 0.2. ► The GaSb phase existed in the skutterudite when the Ga content x = 0.3.