Molten salt methods have been widely used in the synthesis of high-entropy ceramic powders, yet their scalable production for industrial applications is lacking. In this work, for the first time, a densified microzone molten salt (DMMS) approach was developed for the scale-up preparation of high-entropy ceramic powders, including zirconates, hafnates, silicates, and carbides. The “densified” block of DMMS permitted only trace evaporation of molten salt on surfaces, and the internal “microzone” salt pools significantly promoted the in situ formation of high-entropy phases at relatively low temperatures. Single-phase (La_0.2Nd_0.2Sm_0.2Eu_0.2Gd_0.2)₂Zr₂O₇ (HEZO) powders, as an example, could be synthesized with only ~10 wt% volatilization of NaCl–KCl–NaF salt during 1200 °C treatment, while the resulting powders prepared by the traditional powdery method contained segregation phases with a salt loss as high as ~95 wt%. By simply accommodating the “densified” blocks in a tunnel kiln, scale-up synthesis of high-entropy ceramic powders by DMMS can be realized for industrial production.

In this paper, sulfur doped g-C₃N₄ (S-g-C₃N₄) was successfully prepared at 500 ℃ for 3 h via a modified molten salt method using dicyandiamide as the main raw material, trithiocyanuric acid as the sulfur source and LiBr-KCl as the reaction medium. The as-prepared S-CN5.0% sample (the mass ratio of trithiocyanuric acid to dicyandiamide was 5.0%) composed of irregular flakes showed a band gap of 1.83 eV, which was narrower than that (2.55 eV) of pristine g-C₃N₄. The S-CN5.0% sample also exhibited an outstanding absorption capacity of visible light. Moreover, the photodegradation rate toward methylene blue and tetracycline were respectively 10 and 20 times as high as that of bulk g-C₃N₄ prepared by conventional heating methods, confirming its superior photocatalytic performance. These results can be attributed to that the replacement of lattice nitrogen with sulfur atom tuned the electronic structure of g-C₃N₄, improved the absorption of visible light, optimized the separation of photogenerated electron-hole pairs, and consequently enhanced the photocatalytic activity of g-C₃N₄. Moreover, the trapping experiments implied that hole (h⁺) and superoxide radical (·O²⁻) were the main active species in the process of photodegradation.