When exposed to moderate to high temperatures, nanomaterials typically suffer from severe grain coarsening, which has long been a major concern that prevents their wider applications. Here, we proposed an effective strategy to inhibit grain coarsening by constructing grain boundary (GB) complexions with multiple codoped dopants, which hindered coarsening from both energetic and kinetic perspectives. To demonstrate the feasibility of this strategy, multiple selected dopants were doped into a ZrO₂–SiO₂ nanocrystalline glass ceramic (NCGC) to form GB complexions. The results showed that NCGC was predominantly composed of ZrO₂ nanocrystallites (NCs) distributed in an amorphous SiO₂ matrix. Ultrathin layers of GB complexions (~2.5 nm) were formed between adjacent ZrO₂ NCs, and they were crystalline superstructures with co-segregated dopants. In addition, a small amount of quartz solid solution was formed, and it adhered to the periphery of ZrO₂ NCs and bridged the adjacent NCs, acting as a “bridging phase”. The GB complexions and the “bridging phase” synergistically enhanced the coarsening resistance of ZrO₂ NCs up to 1000 °C. These findings are important for understanding GB complexions and are expected to provide new insights into the design of nanomaterials with excellent thermodynamic stability.

Synthetic zircon (ZrSiO₄) ceramics are typically fabricated at elevated temperatures (over 1500 ℃), which would lead to high manufacturing cost. Meanwhile, reports about preparing ZrSiO₄-based ceramic composites via controlling the solid-state reaction between zirconia (ZrO₂) and silica (SiO₂) are limited. In this work, we proposed a low-temperature strategy to flexibly design and fabricate ZrSiO₄-based ceramic composites via doping and tuning the solid-state reaction. Two ceramic composites and ZrSiO₄ ceramics were in-situ prepared by reactive fast hot pressing (FHP) at approximately 1250 ℃ based on the proposed strategy, i.e., a ZrSiO₄–SiO₂ dual-phase composite with bicontinuous interpenetrating and hierarchical microstructures, a ZrSiO₄–ZrO₂ dual-phase composite with a microstructure of ZrO₂ submicron- and nano-particles embedded in a micron ZrSiO₄ matrix, and ZrSiO₄ ceramics with a small amount of residual ZrO₂ nanoparticles. The results showed that the phase compositions, microstructure configurations, mechanical properties, and wear resistance of the materials can be flexibly regulated by the proposed strategy. Hence, ZrSiO₄-based ceramic composites with different properties can be easily fabricated based on different application scenarios. These findings would offer useful guidance for researchers to flexibly fabricate ZrSiO₄-based ceramic composites at low temperatures and tailor their microstructures and properties through doping and tuning the solid-state reaction.