Perovskite ferroelectrics are an important class of functional ceramics. For more than 60 years they are well established materials for charge storage devices and all kinds of piezoelectric components. Increasing demands still drive their development, e.g. currently the quest for lead-free piezoelectric ceramics. Properties of perovskite ferroelectrics can be tailored taking into account the atomic mass of its constituents, which influences the ferroelectric/paraelectric phase transition, and their ionic radii, which are responsible for the symmetry of the lattice. By proper choice of ionic radii advantage of a morphotropic phase boundary can be taken. Donor- or acceptor-doping influences the defect thermodynamics and decides over “hard” or “soft” ferroelectrics. For the further development of ferroelectric ceramics the bonding situation may gain increasing importance. In this paper concepts for covalent or better complex bonding in perovskites are introduced and their consequences for the stability of structures and other material properties are outlined.

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Thermal coagulation therapy using powdered magnetic materials in an alternating (AC) magnetic field has been expected as a treatment of cancerous tissues. For nano-sized superparamagnetic particles, the magnetic energy is mainly converted to a heat generation ability by the rotation of the magnetic moment (Néel relaxation) along with the rotation of the particles (Brownian relaxation). Fe₃O₄ (magnetite) nanoparticles have been mainly investigated as the candidate material for this type of therapy. In this review, an outline of the ferrite materials having heat generation ability in the AC magnetic field is described for the application of the thermal coagulation therapy. In particular, I focused on the preparation of a nano-sized magnetic material using physical bead milling to develop a magnetic material of Y₃Fe₅O₁₂ and its high heat generation ability. The preparation of Y₃Fe₅O₁₂ microspheres with a 20–32 µm diameter range using the bead-milled powder was also described for the embolization method of cancer treatment.

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Cerium oxide is a suitable material for glass polishing because it has both a high chemical reactivity and a suitable hardness for glass polishing. We focused on nano-dispersion abrasives containing two materials that specialize in a chemical reactivity with glass and a suitable mechanical strength and they were synthesized by spray pyrolysis. We first review on CeO₂–ZrO₂–Y₂O₃ nano-composite abrasives that can show you the effect of nano-composition on glass polishing. These nano-composites showed slightly lower removal rate than commercial CeO₂-based abrasive, but the composite led to smooth surface of glass. The nano-dispersed SrZrO₃/ZrO₂ composite particles were then synthesized by spray pyrolysis. The glass polishing using SrZrO₃/ZrO₂ nanocomposite abrasives led to relatively high removal rate and quite smooth surface of glass. The SrZrO₃/CeO₂ abrasives showed superior polishing properties to conventional ceria-based abrasives by adjusting SrZrO₃/CeO₂ ratios. These results revealed that the nano-composition enables us to control mechanical and chemical ratios and this CMP control would lead to develop leading-edge abrasives.

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Many high permittivity crystalline dielectric thin films have a low breakdown strength, which is unfavorable for dielectric energy storage devices. In contrast, many amorphous linear dielectrics have much lower permittivities but larger breakdown strengths. Here, composite thin films with nanocrystalline particles in an amorphous matrix were explored to increase the stored energy density of dielectrics. For this purpose, thin films of lead-rich lead titanate, Pb_1.1TiO_3.1, were fabricated via chemical solution deposition and heat-treated at temperatures ≤400°C. Transmission electron microscopy indicated the presence of dense lead oxide nanocrystals in an amorphous lead titanate network. The films exhibit a relative permittivity of 32.6 and a low dielectric loss of 0.0008. The leakage current is approximately 10⁻⁸ A/cm², with a DC breakdown strength between 2 and 3 MV/cm. The 1 kHz breakdown strength exceeds 5 MV/cm. At an electric field of 5 MV/cm and a measurement frequency of 1 kHz, the maximum in energy storage density was ~28 J/cm³. These properties suggest that nanocomposite Pb_1.1TiO_3.1 films may be a suitable candidate for integration into energy storage devices.

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In this research, Au nanocatalysts were deposited on CuCrO₂ powders using photodeposition to investigate the catalytic activity. Delafossite-type CuCrO₂ porous powders were prepared using a glycine nitrate process. Au nanoparticles were photodeposited onto the CuCrO₂ surface by irradiating light into pH adjusted HAuCl₄ solution. The crystal structure, composition, and micromorphology of the derived Au/CuCrO₂ powders were characterized by X-ray diffraction, X-ray fluorescence, scanning electron microscopy, and transmission electron microscopy (TEM), respectively. TEM observation determined that the diameters of the Au nanoparticles photodeposited on CuCrO₂ powder with UV irradiation at pH = 10 were approximately 4 nm. The differential scanning calorimetric measurement indicated that Au/CuCrO₂ has a catalytic activity of carbon monoxide conversion.

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Materials based on BiMO₃-modified BaTiO₃ have been shown to exhibit a number of attractive electrical and electromechanical properties. In addition, many of the materials in this broad family exhibit reduced sintering temperatures for densification as compared to pure BaTiO₃. We report here a study of the phase evolution and sintering behavior of Bi(Zn_1/2Ti_1/2)O₃-modified BaTiO₃ materials from low-cost mixed oxide/carbonate precursor powders. By accelerating the reaction of the BaCO₃ species and increasing the diffusion kinetics associated with densification, Bi(Zn_1/2Ti_1/2)O₃ additions reduce the calcination and sintering temperatures by ~200°C compared to unmodified BaTiO₃. This system provides an example of the important and often overlooked role of additives in the calcination, phase evolution, and densification processes, and provides insight into mechanisms that may be further exploited in this and other important materials systems. We are quite honored to have the opportunity to publish in a special issue dedicated to the life and work of our dear late colleague Prof. Marija Kosec. The topic of this paper is fitting as well, since the work was in large part directly inspired by her work on the importance of reactions and intermediate phases in the alkali niobate systems and heavily informed by her work on the Pb-based perovskites. Marija appreciated better than most the importance of careful processing in the formation of fine ceramics, and the global ceramics community is grateful to her for all of the lessons that she taught us—and through her papers and her students, continues to teach us.

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We synthesized ZnO nano-particulate films by a sol–gel method and evaluated their gas sensing properties. A ZnO colloidal solution of 5.6 nm sized nanocrystals was prepared from zinc acetate in n-propanol and dip-coated on silica glass substrates. The as-deposited ZnO film consisted of 30 nm grains. Annealing the films resulted in a growth of the particles, which was confirmed by scanning probe microscopy and UV–Vis spectrometry. The ZnO film annealed at 400°C worked well as a gas sensor device for volatile organic compounds (VOC) gases. The sensitivity was the best in the case of ethanol gas at 350°C. The sensing performances decreased by annealing at higher temperatures due to the coalescence of the ZnO particles.

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Dense boron carbide (above 95%) was achieved through high pressure (300 MPa) and low temperature (1600°C) Spark Plasma Sintering (SPS). This approach resulted in improvement of fracture toughness and of dynamic toughness when compared to corresponding toughness values of the sample sintered by conventional SPS (2100°C, 50 MPa). Dynamic toughness was extracted from Split Hopkinson Pressure Bar measurements. Results are understood based on microstructure and on very different behaviour of the samples in respect to residual B₂O₃ and carbon available in the raw B₄C powder.

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Zeolites are commonly used as adsorbents for a wide range of industrial applications. Recently, to alleviate the pressure drop and mass-transfer problems when zeolites are used as pellets in a packed bed system, the need for a self-standing zeolite foam has grown. Therefore, in this study, a zeolite 13X wet foam was stabilized by zeolite 13X particles that were rendered partially hydrophobic by propyl gallate, mixed with a commercial calcium aluminate cement, and then self-set. A self-setting particle-stabilized zeolite 13X foam contains primary macropores with a size range of approximately 200 to 400 µm formed by zeolite 13X particles that are irreversibly adsorbed at liquid–gas interfaces as well as secondary inherent micropores. In addition, we investigated the pore characteristics of the self-setting particle-stabilized zeolite 13X foams by scanning electron micrography, mercury porosimetry, physisorption analysis, and capillary flow porosimetry.

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The 27R-SiAlON crystal with the general formula Si_3−xAl_6+xO_xN_10−x (Z = 3) was characterized using laboratory X-ray powder diffraction (Cu Kα₁) and energy dispersive X-ray spectroscopy. The [Si:Al] molar ratios were determined to be [0.12(1):0.88(1)], corresponding to x = 1.9(1). The Si_1.1(1)Al_7.9(1)O_1.9(1)N_8.1(1) compound is trigonal with space group R3m (centrosymmetric). The hexagonal unit-cell dimensions are a = 0.305991(4) nm, c = 7.1454(1) nm and V = 0.57940(1) nm³. The structural parameters of the initial model were taken from those of 27R-AlON (Al₉O₃N₇), which were subsequently refined by the Rietveld method. The final structural model showed the positional disordering of two of the five types of (Si,Al) sites. The maximum-entropy method-based pattern fitting method was used to confirm the validity of the split-atom model, in which conventional structure bias caused by assuming intensity partitioning was minimized. The disordered crystal structure was successfully described by overlapping five types of domains with ordered atom arrangements. The distribution of atomic positions in one of the five types of domains can be achieved in the space group R3m. The atom arrangements in the four other domains are noncentrosymmetric with the space group R3m. Two of the four types of domains are related by a pseudo-symmetry inversion, and the two remaining domains also have each other the inversion pseudo-symmetry. The very similar domain structure was also reported for 27R-AlON.

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Preparation and magnetic properties were investigated on the Co doped α′′-Fe₁₆N₂ obtained in low temperature nitridation of bcc Fe_1−xCo_x alloys to change its magnetic coercivity. The alloys were prepared by the reduction of (Fe_1−xCo_x)₃O₄ obtained by hydrolysis of iron and cobalt acetylacetonate mixture in benzyl alcohol. Fine powder of the pure spinel-type (Fe_1−xCo_x)₃O₄ was obtained in x = 0–0.05. The oxides were reduced to bcc Fe_1−xCo_x alloy at 400°C in H₂ gas and then nitrided at 150°C for 5 or 8 h under NH₃ gas flow. XRD and X-ray absorption spectroscopy suggested the nominal “α′′-(Fe_1−xCo_x)₁₆N₂”, similar to “α′′-Fe₁₆N₂” was obtained as a mixture with the residual bcc Fe_1−xCo_x alloy at x = 0.03 as in the case of the nitrided product without cobalt. The present nitrided product exhibited a larger magnetization of 217 Am² kg⁻¹ and a smaller magnetic coercivity of 30 mT at x = 0.03 than those for the present products without the Co doping.

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Dense 0.4–5.0 wt % carbon nanofiber (CNF)/alumina composites were fabricated by plasma activated sintering. The microstructure—particularly the CNFs distribution—of composites containing different amounts of CNFs was observed in detail, and the influence of the additive amounts of CNF on the microstructure and the fracture toughness of the composites were investigated. The ratio of CNFs distributed individually in the composites decreased with an increase in the addition of CNFs, and the other CNFs formed bundles; notably three-quarters of the CNFs formed bundles in the 5.0 wt % CNF/alumina composite. The alumina grain size distribution of the composites became narrower to smaller grain size side and the average alumina grain size of the composites decreased with an increase in the addition of CNFs from 0.4 to 1.6 wt %. However, the average alumina grain size of the composites did not vary greatly with an increase in the addition of CNFs from 1.6 to 5.0 wt %, because the CNF bundles formed in the 2.5 and 5.0 wt % CNF/alumina composites lowered the grain growth retardation effect of the CNFs. The 1.6 wt % CNF/alumina composite exhibited the highest fracture toughness, because three-fifths of the CNFs distributed individually and uniformly in alumina grain boundaries.

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Dense and single-phase mullite polycrystals were prepared by reaction sintering of relatively pure kaolins with several kinds of alumina. Removal of coarse kaolin particles >1 µm by sedimentation substantially improved thermal reactivity and sinterability of kaolin and its mixtures with alumina. As for mixtures of refined kaolin and submicron corundum powder having a mullite composition, relative densities of above 98% were accomplished by heat-treatment at 1650°C for 1 h. Effect of alumina particle size on thermal reactivity between alumina and kaolin was investigated, and the difference in thermal reaction sequence between alumina and kaolin was clarified. A combination of sub-micron corundum and elutriated kaolin yielded a monodispersed and fine-grained mullite polycrystals.

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Spinel-type LiTi₂O₄ was prepared directly by the reaction of lepidocrocite-type potassium titanate and molten LiCl at 750–850°C in a stream of H₂ gas. The Li/Ti ratio in the spinel-type phase prepared at 850°C was 0.54, and the lattice parameter and superconductive critical temperature T_c were a = 8.3935(2) Å and 12.3 K, respectively. The product at 750°C exhibited no superconductive diamagnetism down to 2.5 K, and the product at 800°C showed weak superconductive diamagnetism at 10.5 K. The morphology of the particles prepared at 850°C showed an irregular shape with a particle size of 1–10 µm.

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