The NiO/NiCo2O4 mixtures with unique yolk-shell structure were synthesized by a simple hydrothermal route and subsequent thermal treatment. The elemental distribution, composition, and microstructure of the samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and scanning electron microscope (SEM), respectively. The microwave absorption property was investigated by using vector network analysis (VNA). The results indicated that the excellent electromagnetic wave absorption property of the NiO/NiCo2O4 mixtures was achieved due to the unique yolk-shell structure. In detail, the maximum reflection loss (RL) value of the sample reached up to − 37.0 dB at 12.2 GHz and the absorption bandwidth with RL below − 10 dB was 4.0 GHz with a 2.0-mm-thick absorber. In addition, the NiO/NiCo2O4 mixtures prepared at high temperature, exhibited excellent thermal stability. Possible mechanisms were investigated for improving the microwave absorption properties of the samples.

MCo₂O₄ (M = Mn,Ni) microparticles were synthesised by a simple hydrothermal solvothermal method. The samples were characterised by X-ray diffraction, X-ray energy dispersive spectroscopy and scanning electron microscopy, which showed that MnCo₂O₄ microparticles with spherical particles aggregated by a large number of small cubes and cubic shaped NiCo₂O₄ microcubes were obtained. The microwave absorption properties of these products were systematically investigated by vector network analysis. Results indicated that the minimum reflection loss value of MnCo₂O₄ microparticles was −26.34 dB at 11.04 GHz with the absorber thickness of 2.5 mm, which was much lower than that of NiCo₂O₄ microcubes with the same absorber thickness. The possible mechanism was analysed, indicating that the geometry and size of MCo₂O₄ (M = Mn,Ni) microparticles played a key role in microwave absorption.

A novel LaCO₃OH microgear has been synthesized by a green method, which shows strong PL properties.

For growing high quality epitaxial VO₂ thin films, the substrate with suitable lattice parameters is very important if considering the lattice matching. In addition, the thermal conductivity between the substrate and epitaxial film should be also considered. Interestingly, the c-plane of hexagonal 6H-SiC with high thermal conductivity has a similar lattice structure to the VO₂ (010), which enables epitaxial growth of high quality VO₂ films on 6H-SiC substrates. In the current study, we deposited VO₂ thin films directly on 6H-SiC (0001) single-crystal substrates by pulsed laser deposition (PLD) and systematically investigated the crystal structures and surface morphologies of the films as the function of growth temperature and film thickness. With optimized conditions, the obtained epitaxial VO₂ film showed pure monoclinic phase structure and excellent phase transition properties. Across the phase transition from monoclinic structure (M1) to tetragonal rutile structure (R), the VO₂/6H-SiC (0001) film demonstrated a sharp resistance change up to five orders of magnitude and a narrow hysteresis width of only 3.3 °C.

ZrO2 as a wide-bandgap semiconductor with high dielectric constant and ferroelectric properties has been extensively studied. To explore the impact of chemical doping on the structure and optical performance of ZrO2, HfxZr1−xO2 (x = 0, 0.25, 0.5, 0.75, 1) thin films were prepared through pulsed laser deposition. X-ray diffraction reveals that the orthorhombic phase (o) (111) gradually transforms into the monoclinic phase (m) (−111) with the increase in Hf content from 0 to 1. Furthermore, optical property analysis demonstrates an increase in the optical bandgap from 5.17 to 5.68 eV with the increase in Hf doping content. Density functional theory calculations and x-ray photoelectron spectroscopy suggest that the widening of the bandgap in HZO films is associated with the hybridization of Zr 4d and Hf 5d orbitals.