With the rapid development of microelectronics and semiconductor technology, heat dissipation function of device materials has attracted more and more attention in recent years. As one of the promise heat dissipation materials, AlN possesses excellent properties, especially high thermal conductivity. A new process combining sol-gel transformation and polymerization reaction was developed to prepare AlN nanoparticles. With melamine, formaldehyde and boehmite sol as the starting materials, a boehmite-MF composite gel was formed. In this composite, the organic polymer and the inorganic boehmite gel network interacted, so that the carbon source (melamine resin) and aluminum source (boehmite) were mixed homogeneously. Moreover, the composite system inhibited the growth of the aluminum source, hindered the phase transition of alumina, promoted the nitridation reaction to start from the γ-Al₂O₃ directly, and completed nitridation to AlN eventually at 1300 ℃, leading to particles with an average size of less than 30 nm. The activation energy of the carbothermal reduction-nitridation reaction of the system is only 126 kJ·mol^-1, which is much lower than that (360 kJ·mol^-1) of the traditional solid-phase method. Therefore, the simultaneous sol-gel and polymerization process effectively enhanced the reaction.

Solid oxide fuel cell (SOFC) is a clean and efficient energy conversion device, whose performance is closely dependent on the oxygen reduction reaction at the cathode. The traditional high performance cathodes contained cobalt, which have several issues such as high cost, thermal expansion mismatch and poor chemical stability. Therefore, the development of cobalt-free cathode has attracted strong attention in recent years. Perovskite (ABO₃) structured SrFeO_3-δ-based oxide is a good mixed ionic-electronic conductor, which has a great potential to replace the cobalt-based materials. In this review, various elemental doping approaches are summarized, including A-site, B-site and A/B sites co-doping. The effects of doping element and content on the crystal structure, oxygen non-stoichiometric ratio, thermal expansion coefficient, electrical conductivity, oxygen transport property and electrochemical performance of SrFeO_3-δ are discussed. These doping methods could be used as novel strategies for modification of new cobalt-free SOFC cathode materials.

Solid oxide fuel cell (SOFC) has been considered to be one of the most clean and efficient energy conversion devices. However, the market penetration of SOFC still requires continuous materials innovation and fabrication to enhance cell lifespan and reduce cost. At intermediate operating temperatures (500–700 ℃), the polarization loss mainly stems from the oxygen reduction reaction at the cathode. Therefore, it is of great importance to develop new cathodes and new methods with high efficiency and stability. Recently, La_1-xSr_xCo_1-yFe_yO_3-δ (LSCF) has become the wide and practical cathode for intermediate-temperature SOFC, whose physicochemical properties and electrochemical performance have been extensively studied. To further improve its performance and stability, various new electrode fabrication techniques come into view. Surface modification is an effective way to improve the performance and durability of the electrode, which can form a strong interaction between the modification phase and substrate material to have synergistic effect. Research progress in oxide on the surface of LSCF by solution infiltration method will be reviewed. From the point view of modification of binary oxides, ternary oxides and multibasic oxide were discussed, the effects of impregnation on the oxygen ion transport properties, electrochemical performance and long-term stability of substrate materials will be summarized.

Solid oxide fuel cell (SOFC) is a clean and efficient energy conversion device, whose efficiency is dependent on the oxygen reduction reaction at the cathode. The development of high performance cathode materials is the key to increase the efficiency of SOFC. Among Fe-based perovskite cathode materials, BaFeO_3-δ has excellent oxygen transport property. Because the phase transition occurs at the working temperature, it has negative effect on thermal compatibility, conductivity and electro-catalysis performance of BaFeO_3-δ. Owing to the perovskite structure, BaFeO_3-δ could be stabilized through element doping. Element doping at A-site and B-site of BaFeO_3-δ is summarized. The effects of element doping on tolerance factor, crystal structure, conductivity, oxygen non-stoichiometric ratio, coefficient of thermal expansion and electrochemical performance of BaFeO_3-δ are discussed.

Promoting the oxygen reduction reaction (ORR) is critical for commercialization of intermediate-temperature solid oxide fuel cells (IT-SOFCs), where Sr₂Fe_1.5Mo_0.5O_6−δ (SFM) is a promising cathode by working as a mixed ionic and electronic conductor. In this work, doping of In³⁺ greatly increases the oxygen vacancy concentration and the content of adsorbed oxygen species in Sr₂Fe_1.5Mo_0.5−xIn_xO_6−δ (SFMIn_x), and thus effectively promotes the ORR performance. As a typical example, SFMIn_0.1 reduces the polarization resistance (R_p) from 0.089 to 0.046 Ω∙cm² at 800 °C, which is superior to those doped with other metal elements. In addition, SFMIn_0.1 increases the peak power density from 0.92 to 1.47 W∙cm⁻² at 800 °C with humidified H₂ as the fuel, indicating that In³⁺ doping at the Mo site can effectively improve the performance of SOFC cathode material.