The nanostructure control processes based on crystal growth in the solution are introduced. In the main, the self-template method is mentioned. The intermediate compounds such as metal hydroxides obtained by the crystal growth process play a role of self-template. After conversion of intermediate compounds with nanostructure such as nanosheet, the materials with the morphology, which reflects the morphology of the self-template, are obtained. The resultant materials are nanostructured materials with specific morphology. In addition, various nanostructured materials are fabricated by self-template methods through hydrothermal process or flux process. As the applications, dye-sensitized solar cells and Li ion batteries are measured. Moreover, the nanostructure control technique in the solution is used for not only electrochemical devices but also the fabrication of superhydrophobic films.

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Zirconia (ZrO₂) nanoparticles were synthesized at temperature as low as 200°C through a glycothermal reaction using amorphous zirconium hydrous gel precursors and 1,4-butanediol as solvent, XRD and TEM data support that glycothermal processing method provides a simple low temperature route for producing highly crystallized ZrO₂ nanoparticles without mineralizers, which could also be extended to other systems. XRD results also showed that ZrO₂ nanoparticles synthesized in glycothermal condition had tetragonal phase with small portion of monoclinic phase, where the tetragonality was confirmed by Raman spectroscopy. The as-prepared ZrO₂ nanoparticles have spherical morphology with an average crystal size of 10–15 nm and agglomerated into bigger spheres with a diameter of about 100 nm. The tetragonal phase begins to transform to monoclinic phase at 600°C when the calcinations of the as-synthesized powder was carried out.

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This paper presents the preparation of bismuth titanate (Bi₄Ti₃O₁₂; BIT) and praseodymium-substituted bismuth titanate (Bi_4−xPr_xTi₃O₁₂: BPT) with various molarities of praseodymium ion (Pr³⁺: x = 0.2, 0.6 and 1.0) via a fuel-free low-temperature self-combustion synthesis process (FLSC). FLSC offers a remarkable ability to produce polycrystalline BIT powder with an orthorhombic structure, and BPT powder with a tetragonal structure. The substitution of Pr³⁺ into the BIT system retarded the crystal growth, as revealed by the decrease in the crystallite size from 106 to 41 nm by incorporating Pr³⁺ with x = 1.0. Besides, the substitution caused the structure transformation from platelet-like structure to aquiaxed structure. Such structure provides an essential role to enhance the ceramic density. High relative density of about 99.3% was achieved for the BPT ceramic compared to BIT ceramic with a relative density of 89.7%. The results underline the possibility to control the anisotropic grain growth of BIT ceramic by incorporating Pr³⁺ into the BIT system through FLSC. The ceramic sintered at 1100°C exhibited high dielectric permittivity (269.38) with a low dissipation factor as low as 0.00203.

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Hexagonal single crystal silicon carbide was thermally oxidized in pure oxygen and in air at 1473 K. The thermally formed oxide scales were composed mostly of amorphous silica. However, some crystalline phase oxide scales were observed randomly distributed on the formed oxide scale. The ratio of crystalline scale to overall oxide scale was less than 5 percent. We characterized the microstructures of the thermally formed oxide scales using transmission electron microscopy with low-dose observation technique. The oxide scales in some regions were divided into two layers, with crystalline scale on the upper and amorphous scale on the lower layer. Traces of calcium were found in the crystalline phase oxide scale, which could have influenced the crystallization.

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Nanometric-sized strontium doped ceria powders were prepared by combustion glycine-nitrate procedure. Cerium nitrate and strontium nitrate were used as starting material whereas glycine is used as a fuel. The tailored composition was: Ce_1−xSr_xO_2−δ with concentration “x” ranging from 0 to 0.15. The effect of dopant concentration and subsequent calcination on crystal stability and lattice parameter was studied. Results showed that the obtained powders were solid solutions with a fluorite-type crystal structure. The particle size was in the nanometric range (<15 nm). Calcination of as-prepared powders at 850°C caused the formation of secondary phase (SrCeO₃) in samples containing with fraction of Sr²⁺ ions ≥9 mol %. The solubility limit of Sr²⁺ ions in ceria lattice was between 6 and 9 mol % at 850°C. The solid solution of 6 mol % Sr²⁺ was stable even at temperature as high as 1550°C.

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La_9.33+x/3Si_6−xAl_xO₂₆ (0 ≤ x ≤ 2.0) sinters with an apatite-type crystal structure were synthesized by solid-state reaction at 1600°C for 5 h, and the sintered discs were examined by AC impedance analysis and X-ray Diffraction (XRD). The total conductivity was significantly increased with an increase in the Al-content and showed a maximum value for x = 1.5 (8.8 × 10⁻³ S cm⁻¹ at 700°C). The crystal structure model can refine the profiles obtained by XRD with the P6₃ space group and the channel oxygen atoms were displaced from the ideal site at (0, 0, ≈0.25) with an increase in the Al-content and showed a maximum displacement for x = 1.5. These results show that the position of the channel oxygen atoms is the key parameter that governed the conductivity.

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Determined by the strength, flowability, and microstructure of the granules, the optimization of additive contents and presintering conditions for Si-additive mixture granules was assessed. Excessive additive contents led to a low granular strength and poor flowability due to the formation of large agglomerates and voids. The optimum presintering temperature for a 3 wt % Y₂O₃–Al₂O₃–CaO system was found between 1300 and 1375°C. Temperatures below and above the optimum temperature range resulted in low strength and poor flowability, respectively. The packing configuration by porous granules was modeled to calculate the intergranular porosity and intragranular porosity out of the total porosity.

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Iron niobate (FeNbO₄) nanospheres of an orthorhombic structure were synthesized using a hydrothermal (HT) process at 250°C, and were characterized using X-ray diffraction, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, and Brunauer–Emmett–Teller (BET) measurements. The FeNbO₄ nanospheres obtained through the HT reaction revealed a uniform size with an average diameter of 5–10 nm, and a larger specific surface area (82.72 m² g⁻¹) than that of bulk FeNbO₄ powder (2.51 m² g⁻¹) prepared by a solid-state reaction. In addition, the electrochemical properties of the FeNbO₄ powders versus Li were evaluated using cyclic voltammetry and galvanostatic charge/discharge cycling. Importantly, the FeNbO₄ nanospheres delivered a reversible capacity of over 200 mAh g⁻¹ after 20 cycles, and provided an enhanced rate capability compared to the bulk material.

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