The synthesis and microstructure of CuFeO₂ powders via microwave hydrothermal reaction

Abstract

The CuFeO 2 powders have been synthesized by the microwave hydrothermal reaction at different reaction temperatures. The pure rhombohedral phase for CuFeO 2 has been formed and confirmed by the X-ray diffraction (XRD). The microstructure and morphology for all CuFeO 2 samples have been scanned by the Transmission Electronic Microscope (TEM). Various scales of grains for powders have been found spanning from several nanometers to hundreds of nanometers, and even few scales are over 1¯m for some grains. The average grain sizes for all powders have been calculated basing on the XRD patterns to show the changing of grain sizes with the temperature. The distributions of the grain size have also been studied by counting grain numbers from the TEM images. Based on the above results, the mechanism of grain growth has been analyzed and found to be the classical Ostwald ripening.

Synthesis and Performance of Large-Scale Cost-Effective Environment-Friendly Nanostructured Thermoelectric Materials

“…Then, the powders were treated in Argon flow at 573 K for 2 h and then spark plasma sintered under 40 MPa axial pressure at 623 K for 5 min to give the highest ZT of 0.82. Zhai et al [39] found that the grain growth in CuFeO2 powders synthesized by the microwave hydrothermal (MH) reaction satisfied the theory of classical Ostwald ripening, and a pure rhombohedral phase in the material has been formed, as shown in Figure 1e. Nanostructured particles of size in the range 50-100 nm were formed in Ga-doped ZnO made by the MH technique [40].…”

“…Point defects in Zr, Sn, or Hf, Sn co-doped Cu 3 SbSe 4 nanoparticles can be seen in Figure 1 g. Then, the powders were treated in Argon flow at 573 K for 2 h and then spark plasma sintered under 40 MPa axial pressure at 623 K for 5 min to give the highest ZT of 0.82. Zhai et al [ 39 ] found that the grain growth in CuFeO2 powders synthesized by the microwave hydrothermal (MH) reaction satisfied the theory of classical Ostwald ripening, and a pure rhombohedral phase in the material has been formed, as shown in Figure 1 e. Nanostructured particles of size in the range 50–100 nm were formed in Ga-doped ZnO made by the MH technique [ 40 ]. A one-step MH procedure was used to prepare phase-pure polycrystalline Sn 1- δ S with a high ZT of 0.76 at 523 K due to relatively good mobility and high carrier concentration [ 41 ].…”

“…Copyright Royal Society of Chemistry, 2020, ( e ) The classical Ostwald ripening progress in CuFeO2 powders synthesized by MH reaction. Reproduced with permission from [ 39 ]. Copyright Journal of the Ceramic Society of Japan, 2019, ( f ) Tin telluride nanoparticles (NP) synthesized by MH method and building blocks of SnTe after SPS.…”