Rotary chemical vapor deposition (CVD) is a non-line-of-sight-deposition process with excellent coverage and a versatile technique to modify surfaces of ceramic powders. In this paper, potential applications of rotary CVD for coatings on powders are presented; highly dispersive catalytic nanoparticles can be deposited on support powders, while the conformal thin layers can be coated uniformly on particulates, which are advantageous in powder metallurgy for the preparation of sintered bulk materials. Particularly, this paper focuses on the deposition of silicon carbide (SiC) layers on silica (SiO₂) and diamond particles using the rotary CVD technique; the resultant core/shell powders are readily sintered using spark plasma sintering at moderate temperatures and pressures. The CVD-SiC layers formed on powders prevent grain growth and act as protective layers against reactions and phase transformations at the sintering temperatures, resulting in the formation of a discriminating microstructure with enhanced mechanical properties.

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Optically transparent and electrically conductive glass-ceramics have been successfully prepared from 1Na₂O–0.5MnO–0.5FeO–1SiO₂ (Na₂Mn_0.5Fe_0.5SiO₄) glass by heat-treatment. Crystallization tendency was sensitive to the valence state of transition metal oxide. The as-quenched glass melted at 1400°C for 15 min, exhibited two exothermic peaks in the differential thermal analysis. Optically transparent glass-ceramics obtained at 493°C for 3 h showed simple X-ray diffraction pattern, which could be assigned to a cubic phase with a lattice constant of 0.74511 nm. A monoclinic Na₂MSiO₄ (M = Mn, Fe) phase appeared with the heat treatment above 610°C, suggesting that the crystal phase precipitated in the low temperature region was thermodynamically metastable. The transparent glass-ceramics showed an order of magnitude higher electrical conductivity than that of glass and the monoclinic phase.

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The most common preparative method for inorganic solids is solid state reaction of constituent materials. Since the solid state reaction is usually performed at high temperature for a long heating duration, almost all the products are thermodynamically stable. During the long history of solid state chemistry and materials science, an enormous number of binary and ternary equilibrium phase diagrams were constructed and it seems like there is no hope to find out new materials those exhibit fascinating functionality. By applying external fields to solid state reaction systems, however, it has become possible to synthesize new compounds those do not exist in the equilibrium phase diagrams. In this article, synthesis of inorganic materials under high-pressure and microwave electromagnetic fields is reviewed. The scope of this review covers, but is not limited to, effects of external fields (high-pressure and microwave electromagnetic wave) on the formation of new compounds and structures those can not be prepared by conventional synthetic routes.

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In this paper, we investigated the effects of calcium contents on the sintering behaviors, phase composition, microstructure and microwave dielectric properties of Li₂Zn₃Ti₄O₁₂ (LZT) ceramics to find temperature stable and high quality factor (Q×f) microwave ceramics. The X-ray diffraction (XRD) results indicated the LZT and CaTiO₃ co-existed with each other and formed a stable composite system when the calcium was added. Scanning electron microscopy photographs also demonstrated the existence of CaTiO₃ phase, which were consistent with the XRD results. With the increasing calcium content, the apparent density decreased from 4.38 to 4.28 g/cm³, the dielectric constant (ε_r) increased from 19.3 to 23.9, Q×f decreased from 74344 to 42264 GHz, and the temperature coefficient of resonant frequency (τ_f) was significantly improved from −48 to +9.12 ppm/°C due to the increasing amount of CaTiO₃ phase. At last, the (Li₂Zn_2.72Ti_3.72O_11.16)–0.28CaTiO₃ ceramics sintered at 1200°C for 4 h displayed the excellent comprehensive properties of ε_r = 23.5, Q×f = 55604 GHz and τ_f = 0 ppm/°C.

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Lead-free piezoelectric ceramics (Ba_0.85C_0.15−xBi_x)(Zr_0.1Ti_0.90)O₃ system were synthesized by conventional solid-state reaction. The structure, dielectric, ferroelectric and piezoelectric properties have been investigated in detail. X-ray diffraction analysis revealed that all specimens displayed typical perovskite structure at room temperature. Scanning electron microscope results showed that the introduction of Bi element could effectively reduce the sintering temperature and favor grain refinement of BCZT ceramics. Dielectric measurements displayed that a typical relaxor behavior was appeared and dramatically enhanced with Bi concentration, which is mainly owing to the composition fluctuation and structural fluctuation after Bi introduction. The maximum relaxation degree (γ = 1.9326) was obtained with the sample of x = 0.05. The ferroelectric properties combined with current-electric field illustrated that the P–E loops became slimmer and leaner, meanwhile J–E curves gradually changed to be a broad and flat current platform. The variation of ferroelectric behavior was closely related with the emergence of relaxation behavior in (Ba_0.85Ca_0.15−xBi_x)(Zr_0.1Ti_0.9)O₃ ceramics.

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Yb₃Al₅O₁₂ and Yb₃Ga₅O₁₂ ceramics for emitters of thermophotovoltaic systems were made by solid-state reaction. Thermal radiation measurements revealed that the sufficiently porous ceramics had excellent selectivity regarding emission wavelengths. Generally, in spite of the narrow-band thermal emission of rare-earth ions, most ceramics do not present sufficient selectivity because of their transparency in the near infrared range. We discuss a mechanism for high selectivity from observing the microstructures of these developed ceramics.

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Glass formation was investigated for the Ga₂S₃–Sb₂S₃–CsX (X = Cl, Br, I) and Ga₂S₃–Sb₂S₃–AgCl systems. Glasses were obtained for the compositional regions that contain the parts of the lines from the eutectic point of the Ga₂S₃–Sb₂S₃ system (20GaS_3/2·80SbS_3/2) to the midpoint of the GaS_3/2–CsX system (50GaS_3/2·50CsX), extending to both sides of the lines. The glass transition temperatures were in the range of 210 to 280°C and tended to decrease with increases of the Sb₂S₃ and CsX contents. Some glasses in these systems had a temperature difference between crystallization and a glass transition of more than 200 K. The infrared transmission limits were located at approximately 14 µm, and the transmission range covered the atmospheric windows. These facts indicate that the glasses are suitable for use as optical materials in infrared optics. Furthermore, the absorption edges at the short wavelength side were blue-shifted, reaching the visible region with the incorporation of CsX. However, glasses in some compositional domains showed inhomogeneous structures in their matrices. Particularly, a unique morphology was observed the inhomogeneous CsCl-incorporated glasses, in which many voids of several micrometers in size were formed. The crystallization behaviors at the borders of the glass forming regions are discussed.

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Octacalcium phosphate (OCP) has a layered structure consisting of apatitic and hydrated layers. The hydrogen phosphate ions in the hydrated layer can be replaced by dicarboxylate ions resulting in the formation of OCP with incorporated dicarboxylate ions. We herein report the transformation behaviour of dicalcium phosphate dihydrate (DCPD), which is used as starting material for the synthesis of OCP in acetic acid (Ace), succinic acid (Suc), suberic acid (Sub), and isophthalic acid (Isp) solutions at a pH of approximately 5.5 at 60°C. We found that DCPD with a small crystal size (specific surface area: 4.9 m²·g⁻¹) completely transformed into OCP within 1 h in Ace solution, whereas DCPD with a large crystal size (specific surface area: 0.62 m²·g⁻¹) did not form the OCP phase even when treated for 3 h. OCP incorporating Suc and Isp was formed from DCPD with a small crystal size in solutions of these dicarboxylic acids. On the other hand, Sub was not incorporated into OCP although Sub is a typical dicarboxylic acid that could be incorporated into the OCP structure. We concluded that although the dicarboxylic acids that are adaptable to these experimental conditions are limited, DCPD can be used as a starting material for OCP with incorporated dicarboxylate ions.

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In this study, we investigated the relationship between the structural changes and wetting properties of porcelain enamel doped with CoO. Glass with the composition 45SiO₂–15B₂O₅–25NaO–15CaO was doped with different CoO concentrations. The wetting properties were characterized by high-temperature microscopy and the structural changes were observed by scanning electron microscopy, X-ray photoelectron spectroscopy, electron probe microanalysis, Fourier transform infrared spectroscopy, and energy dispersive X-ray spectroscopy. CoO addition increased the number of non-bridging oxygen atoms in the glass system, as well as the wetting ability. The addition of CoO to the porcelain enamel not only increased adherence, but also decreased the sintering temperature.

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Sodium rechargeable batteries using earth-abundant raw material sources are more suitable for wide application as compared to lithium batteries. The development of inorganic solid electrolytes with high Na-ion conductivity is indispensable to realize all-solid-state sodium batteries. The sulfide solid electrolyte with cubic Na₃PS₄ phase has a high sodium-ion conductivity at room temperature. This research has addressed, for the first time, the preparation of Na₃PS₄ electrolyte thin films using pulsed laser deposition, to be applied in bulk-type all-solid-state sodium batteries. The heat-treated Na₃PS₄ thin film exhibited a conductivity of 3.5 × 10⁻⁵ S cm⁻¹ at 25°C and the activation energy for conduction was calculated to be 45 kJ mol⁻¹. The active material in the form of NaCrO₂ particles coated with Na₃PS₄ thin film was applied in all-solid-state batteries, which functioned as a sodium secondary battery at room temperature.

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Sr₂MgMoO_6−δ (SMM) is one of promising anode materials for direct internal reforming solid oxide fuel cells as its excellent performance has been demonstrated. However, it is necessary to be chemically compatible with the electrolyte material to realize the original performance. In this study, we investigate chemical compatibility between SMM and typical electrolyte materials (8% mol Y₂O₃–92% mol ZrO₂; YSZ, 10% mol Sc₂O₃–1% mol CeO₂–89% mol ZrO₂; ScSZ, La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ; LSGM) and anode interlayer materials (Gd_0.1Ce_0.9O_2−δ; GDC, Ce_0.8La_0.2O_2−δ; LDC) under conditions for preparing SMM electrode and operation. SMM formed a reaction layer with all of the typical electrolyte materials studied. LDC was the only material for the interlayer that maintains chemical compatibility with SMM, though it forms the reaction layer with YSZ and ScSZ. From these results, this study clarifies that LSGM and LDC should be used as electrolyte and interlayer, respectively, when SMM is used as the anode.

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Alumina bubble ceramics is a light-weight high-strength thermal insulation material of excellent properties with a wide-range application. Binder is the key to its preparation. Binder enables the alumina bubbles to be bonded together to form alumina bubble ceramics with mechanical properties. We report a new method of preparing alumina bubble ceramics with a binder precursor—silicone rubber. The transition of silicone rubber from organic to inorganic substance occurs during the sintering process. Moreover, the binder formed during the transformation coated and bonded alumina bubbles well. Compressive strength of prepared samples was up to 7.5 MPa. For their light weight, high strength, such materials can be adopted as thermal insulations, with prospective application for spacecraft thermal sealing. Due to the good molding characteristic, excellent green body elasticity, and high machinability, this method can be used to prepare samples of complex shapes and precise dimensions.

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