A series of intergrowth bismuth-layered (Bi3TiNbO9)2(Bi4Ti3O12)1 ceramics were reactive-sintered to infer their structural characters and microstructural relationship. Combined with XRD and STEM analysis, the long-range-disordered structures were found in this compound accompanied by obvious kinetic effect. Detail study showed that the inhomogeneous liquid phase composition before grain growth-interface induces the emergence of various intergrowth structures. The further epitaxial growth of these potential structures along c-direction builds up the long-range-disordered intergrowth grains. Meanwhile, such growth features make it hard for the (Bi3TiNbO9)2(Bi4Ti3O12)1 system to obtain long-range-ordered intergrowth structure by a conventional solid-state reaction method.

VO2 thin films grown on SiOx/Si substrates have been characterized at the sub-nanometer level by Cs-corrected scanning transmission electron microscopy along with electron energy loss spectroscopy. Reduced transitional regions of 2–3 nm thick were found at both the surface and the interface, where the vanadium valence progressively changes from +4 to +2. The formation of these nanometer-thick surficial and interfacial layers can be interpreted as a unique case of prewetting, and it explains the degradation of metal-to-insulator transition properties in VO2 thin films.

A comparative study of phase components and compositions was performed for the pressureless sintered HfB2–SiC–WC composites by various analytical methods. The relative decrease of HfB2 phase leads to a new reaction of HfO2 removal by WC to create B2O3. By using SiC instead of Si3N4 as milling medium, the WB phase was suppressed to the trace level while the W solid-solution in HfB2 phase was favored. The W solution in both the primary HfB2 and resultant HfC phases indicates that the WC additive was involved throughout the sintering process by dissolving into sintering liquid, which remains at the intergranular regions to form amorphous oxides as well as trace W-rich phases. This is effectively a reactive liquid-phase sintering to realize the reaction, solid-solution and densification collectively to achieve a designable HfB2–SiC–HfC composite by pressureless sintering, which may also be extended to other sintering methods.

Inner pore channels were commonly found in precursor-derived Si–C–N ceramics. After annealing in air at 1420 °C, their oxidation structures were investigated by analytical TEM. A carbon-rich ring was frequently observed under the silica layer inside the pore channels, which consisted of graphite-like clusters in size of 20–30 nm. Origin of such interfacial structure is due to the excessive free-carbon in the amorphous Si–C–N matrix that had survived the oxidation process. This graphitic interface could further improve the oxidation resistance of the SiO2 over-layer. This novel interfacial structure was also found by annealing in N2, reaffirming the effect of composition of Si–C–N matrix.

Quantitative analytical electron microscopy study of dopant distribution in the microstructure of selected Nd-α-sialon samples revealed the presence of relatively large amounts of glassy phase at quadruple pockets, which exhibited a common composition similar to a melilite solution. Al segregants were depleted from adjacent grain boundaries to satisfy the “stoichiometry” of such glass. Existence of this glass results in significant deviation of the Nd-α-sialon composition from the expected values, which shifts the α-β-sialon phase boundary. Only extra Nd2O3 additives enable a monolithic α-sialon microstructure. The absence of similar glass in Yb-α-sialon materials keeps the phase relations from such deviations.

It was previously found that CaO additives in Si3N4 containing SiO2 segregate to the ∼1 nm thin amorphous grain boundaries in preference to dissolving in the interior of the SiO2 rich glass pockets. Moreover, Ca was detected at some of the β-Si3N4/silica interfaces. Using sensitive imaging and analytical methods available from modern transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM), the Ca distribution was accurately mapped with a resolution approaching 1 nm. Liquid–liquid phase separation occurs at the liquid (now glass) triple pockets at higher Ca levels. Electron energy-loss spectrometry provides compositions of the separated phases, one being nearly pure SiO2 and the other containing significant Ca and N, and also insights about their bonding nature. The Ca and N containing liquid tends to reside in the tips of the liquid pockets with re-entrant geometries. The two β-Si3N4/liquid interfaces and the actual triple line regions were also assessed. Evidence emerged that these entities are diffuse spanning well more than a nanometer in width and having high N levels; Ca also often adsorbs to these. The β-Si3N4/liquid interfaces for the two liquids have different compositions, and that of the grain boundary film is intermediate between these values. Thus, this chemical information yields a comprehensive picture of this phase separation and of the various interfaces in this system.