High functionalization of materials by the combination of heterogeneous substances has become an important procedure for the development of high-performance materials. In various procedures for composite processes, the phase separation of glasses has a potential for use with combinations of the varieties of functional materials spontaneously in nanometer and micrometer scale. Moreover, because phase separation is applicable not only to glass–glass combinations but also to glass–crystal combinations which can control both crystalline phase and inside structure of the composite simultaneously, the utilization of phase separation becomes an interesting and effective technique to create novel high-performance composite materials. In this review, the phase separation of inorganic glasses and glass ceramics mainly caused by stable immiscibility phenomena in high-temperature melts and their applications to the preparation of the high-performance composites are summarized. The preparation procedures and the performances of the materials in silicate systems were described specifically, centering on the studies of the author’s group such as luminous, magnetic, and photocatalytic materials.

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The effects of the pre-treatment of commercially available powder by high energy ball milling on the densification of highly refractory ZrB₂ were investigated. The pristine powder could be crushed into 10 nm in size by high energy ball milling. The resultant powder was densified, using spark plasma sintering apparatus under 120 MPa pressure. Dense ZrB₂ with fine microstructure was obtained after sintering at 1425°C for 1 h. The ultra-fine particle size of crushed ZrB₂, and the deformation of the powders and grains by dislocation played important roles in the low temperature densification of the pre-treated ZrB₂ powder. WC, which was incorporated during the milling process from WC–Co balls, formed a solid solution with ZrB₂, and promoted grain growth at and above 1450°C. In contrast, Co was mostly segregated at the grain boundary. The 4-point bending strength of the specimens sintered at 1450°C was 481 MPa. The densification of ZrB₂ could be strongly promoted by high energy ball milling treatment of the raw powder, and the resultant specimens had good mechanical properties.

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A Liquid-Phase Precursor method followed by a 5% KOH solution treatment was employed for the facile synthesis of Y(V,P)O₄:Eu³⁺@amorphous-K-VO₃ core/shell nanophosphors with non-stoichiometric composition Y_x(V_0.44P_0.56)O₄:Eu_0.1 (x = 0.855, 0.875, 0.90 and 0.965). It was observed that this non-stoichiometric composition approach leads to the control of the size, shape and unit cell parameters depending upon the Y concentration. The shell layer of 2–7 nm formed by alkaline solution treatment at room-temperature was observed by Transmission Electron Microscope (TEM). The particle size grew up by 20–50 nm and the luminescence properties were enhanced by 9–31% after the KOH solution treatment. In contrast, the micro-sized Y(V,P)O₄:Eu³⁺ phosphors treated by the KOH solution did not show any change in their luminescence properties. This KOH solution treatment opens new possibilities to facilely synthesize Y(V,P)O₄:Eu³⁺@amorphous-K-VO₃ core/shell nanophosphors with highly stable properties and improved luminescence.

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This paper reports fabrication of transparent self-supporting alumina films by using homogeneous precipitation and peptization processes. White precipitate of aluminum hydroxide was prepared with a homogeneous precipitation method using aluminum nitrate and urea in aqueous solution. The obtained aluminum hydroxide precipitate was peptized by using acetic acid at room temperature, which resulted in production of a transparent alumina sol. The alumina sol was transformed to an alumina gel film by drying the sol at room temperature. The alumina film was amorphous or fine crystallites even after annealed at a temperature as high as 500°C, and was crystallized to γ-Al₂O₃ at 900°C.

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A yellow-emitting Eu²⁺-doped Ca-α-SiAlON phosphor is a promising candidate to make white LEDs by combining with blue LED. In the current research, the effect of flux (NH₄Cl or NH₄F) addition on the Ca-α-SiAlON:Eu²⁺ phosphor was investigated. The formation of both the compound and liquid phase between the flux and raw materials resulted in the decreased photoluminescence (PL) intensity in the early stage. However, the subsequent melting of second phases and retarded crystallization enhanced the PL intensity with increasing the synthesis temperature and time. The increased PL intensity for the flux-added compositions is attributed to the less surface damages due to grinding of as-synthesized agglomerate-like phosphors. Further, the flux addition enhanced the particle growth by forming agglomerates in the early stage and it also influenced the particle morphology from the typical acicular shape to pseudo-equiaxed shape.

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Cubic shaped YBO₃:Tb³⁺ green phosphor was synthesized by precipitation from homogeneous solution. Prepared precipitates were identified as Y[B(OH)₄](CO₃) by X-ray diffraction, and cubic shaped particles of about 2 µm were observed by a scanning electron microscope. By heating at 800°C, the cubic shape of the particles was kept and YBO₃ was obtained. Tb-doped YBO₃ samples which were controlled as cubic shaped particles showed bright green emission by UV excitation.

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Monodispersed BaTiO₃ nanoparticles with an average grain size of 3–5 nm were obtained by a convenient one-step solvothermal method. In this method, the crucial step to achieve ultrafine BaTiO₃ nanoparticles is the control of hydrolysis of Ti(OC₄H₉)₄ by Diethylene glycol (DEG). DEG can strongly inhibit the hydrolysis procedure and prevent the grain growth of BaTiO₃ nanoparticles. Ba(OH)₂·8H₂O provides H₂O source and alkaline environment. Polyvinyl pyrrolidone (PVP) is used as surfactant. The as-prepared monodispersed BaTiO₃ nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), BET-specific surface area measurement, fouriertransform infrared (FT-IR) spectrum and X-ray photoelectron spectroscopy (XPS). The influence of concentration, temperature, time and the importance of PVP were explored to investigate the growth-up mechanism of the BaTiO₃ nanoparticles.

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We investigated the detailed charge injection properties of a metal (Pt)/insulator (Cr₂O₃)/floating gate layer (Cr₂O_3−x)/magnetic filtering layer/tunnel layer (CeO₂)/semiconductor (Si) capacitor. This capacitor shows charge injection type capacitance–voltage (C–V) properties with a hysteresis window. The hysteresis window width (HWW) can be controlled by an external electric or magnetic field. Changes in the HWW are determined by the combined spin density of state of a spin filter layer and a floating gate. Our results indicate that this capacitor may be able to electromagnetically store multiple charges.

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We describe a method for fabricating a large-scale homogeneous porous alumina membrane as a mask for dry etching of the large surface area (of the order of one square centimeter) of a semi-insulating semiconductor substrate. It employs direct anodization of the aluminum layer deposited on the substrate, which is simple, therefore, suitable for high-throughput productions. However, the process with a non-conductive semiconductor substrate suffers from the issues of quality control of the pores caused by nonuniform current flow in the aluminum layer in the anodization process. Hence, we have implemented a new fitting to the anode that provides uniform current flow into the aluminum layer, which allows us to fabricate highly homogeneous nanopores on the large-scale alumina membrane.

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The polyborosilazane (PBSZ) was employed as the sintering additive and the dense ZrB₂ ultra-high temperature ceramic samples were fabricated by hot pressing at 1900°C. The relative density of sintered ceramics is 96.4%. The PBSZ was converted to amorphous SiBCN ceramics after sintering. Mass transfer process was significantly improved in the amorphous region among the ZrB₂ grains. Densification temperature was reduced. The mechanical properties and high temperature oxidation resistance were also enhanced. The bending strength and fracture toughness of the ZrB₂ ceramics were 241 ± 10 MPa and 4.47 ± 0.5 MPa m^1/2, respectively. The crack was deflected along the grain boundaries. During high-temperature oxidation process, the grain boundary at SiBCN ceramic was oxidized into borosilicate glass and the low viscous glass was extruded out and spread over the surface quickly. The continuous oxide coating formed on the ZrB₂ ceramics surface prevented further oxidation.

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Electrical heating of the graphite die and punch assembly is a unique feature of the spark plasma sintering (SPS) process. The high currents needed to heat the die, despite its low resistance, can produce an electric field across the ceramic specimens that may be enough to induce field assisted sintering. Despite the large number of publications of SPS, the electric field intensity has not been accounted in previous investigations. A FEM model is employed to quantify the magnitude of electric field applied during sintering across zirconia sample. We show that the electric field depends most critically on the ratio of the outer and inner diameter of the die. We also report that the intensity of the electric field across the sintering sample is significantly affected by duty cycle of the pulsed current.

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