Ceramics

This paper considers the results of an examination of a polychrome glazed anthropomorphic ceramic figurine from the Prmor’ye region (southern Russian Far East) discovered at one of the Jin period (1115–1234 CE) archaeological sites. The study attests to the hypothesis about the attribution of this unique art object to the “red-and-green porcelain” produced in Northern China since the mid-Jin period. At present “the red-and-green porcelain” is the object of certain research interest as an important stage of Chinese ceramics history preceding the invention of famous porcelains with overglazed enamel decoration. The main technological features and material properties of the studied object were determined using analytical methods of optical and electron (SEM) microscopy with the use of X-ray elemental composition analysis (EDS, pXRF). The main result of the study presented in the paper includes evidence that the polychrome ceramic figurine found at the Anan’evka walled town in Primor’ey in the south of the Russian Far East belongs to the category of “red-and-green porcelain”, or “red-green ware”. As supposed, the figurine portrays Zen monk Budai—a person popular in Chinese arts and spiritual culture of the Song and Jin periods. Therefore, the polychrome ceramics figurine from the Primor’ye region may be considered today as the most northeastern case of “red-and-green porcelain” discovered in an archaeological context. Full article

P-type delafossite CuGaO₂ is a wide-bandgap semiconductor for optoelectronic applications, and its lattice parameters are very similar to those of n-type semiconductor wurtzite ZnO. Accordingly, the investigation of crystalline heterostructures of CuGaO₂ and ZnO has attracted significant attention. In this study, interfacial CuGaO₂/ZnO hetero-compounds were examined through X-ray diffraction (XRD) analysis, confocal micro-Raman spectroscopy, and X-ray photo-electron spectroscopy (XPS). XRD and Raman analysis revealed that the hydrothermal deposition of ZnO on hexagonal platelet CuGaO₂ base crystals was successful, and the subsequent reduction process could induce a unique, unprecedented reaction between CuGaO₂ and ZnO, depending on the deposition parameters. XPS allowed the comparison of the binding energies (peak position and width) of the core level electrons of the constituents (Cu, Ga, Zn, and O) of the pristine CuGaO₂ single crystallites and interfacial CuGaO₂/ZnO hybrids. The presences of Cu²⁺ ions and strained GaO₆ octahedra were the main characteristics of the CuGaO₂/ZnO hybrid interface. The XPS and modified Auger parameter analysis gave an insight into a specific polarization of the interface, promising for further development of CuGaO₂/ZnO hybrids. Full article

Solid oxide fuel cells (SOFCs) are promising devices for electrical power generation from hydrogen or hydrocarbon fuels. The paper reports our study of CaO-SiO₂-B₂O₃ material with composition 36 mol.% SiO₂, 26 mol.% B₂O₃, and 38 mol.% CaO as a high-temperature sealant for SOFCs with an operating temperature of 850 °C. The material was studied as an alternative to presently existing commercial glass and glass-ceramics sealants for SOFCs with operating temperature of 850 °C. Many of these sealants have limited adhesion to the surface of Crofer 22APU steel, commonly used in these SOFCs. The present study included X-ray diffraction, dilatometric, thermal, and microstructural analysis The study has shown that the softening point of the CaO-SiO₂-B₂O₃ glass is around 900 °C, allowing sealing of the SOFCs with this glass at convenient temperature of 925 °C. The CaO-SiO₂-B₂O₃ glass sealant has shown excellent adhesion to the surface of Crofer 22APU steel; SEM images demonstrated evidences of chemical reaction and formation of strong interface on sealant–steel contact surface. Furthermore, the glass has shown a coefficient of thermal expansion about 8.4 × 10⁻⁶ 1/K after sealing, making it thermomechanically compatible with the existing SOFC materials. Full article

A high NIR reflectance ceramic pigments palette based on rare earths except black (La,Li-SrCuSi₄O₁₀ blue wesselsite, Pr-CeO₂ red-brown cerianite, Mo-Y₂Ce₂O₇ yellow cerate, Sr₄Mn₂CuO₉ black hexagonal perovskite) was compared with the coolest traditional pigments palette prepared by dry powder coating (DPC) to obtain “core-shell” pigments (Co-willemite blue, Cr-franklinite brown, Ni,Sb-rutile yellow, Co,Cr-spinel black). Adding CaCO₃ as a binder, normalized NIR reflectance at L* = 85, 55 and 30 was compared for yellow, brown and blue-black powders, respectively. Rare earths lack intense absorption bands in the NIR range and therefore its pigments show higher NIR reflectance, but normalized measurements show smaller differences and even have an inverse result for blue pigments. The pigmenting capacity and stability study in different media show that the stability of cool rare earth pigments is lower than that of DPC classical pigments, except in the case of the red-brown Pr-cerianite pigment. Full article

Thin films of Sr_0.98Zr_0.95Y_0.05O_3−δ (SZY) electrolyte were grown on porous supporting SrTi_0.8Fe_0.2O_3−δ electrodes by the chemical solution deposition method from a low-viscous solution of inorganic salts. The films were characterized by X-ray diffraction and scanning electron microscopy. The gas-tightness of the films was evaluated using the differential-pressure method. The across-plane electrical conductivity of 1 mm thick SZY film was measured by impedance spectroscopy and compared to that of a massive ceramic sample. The revealed difference in electrical properties of the film and massive SZY samples indicates that diffusional interaction between the film and the substrate influences the performance of the supported electrolyte. Full article

Porosity is a key feature in dictating the overall performance of biomedical scaffolds, with special relevance to mechanical properties. Usually, compressive strength and elastic modulus are the main parameters used to determine the potential mechanical suitability of porous scaffolds for bone repair. However, their assessment may not be so easy from an experimental viewpoint and, especially if the porosity is high, so reliable for brittle bioceramic foams. Hence, assessing the relationship between porosity and mechanical properties based only on the constitutive parameters of the solid material is a challenging and important task to predict the scaffold performance for optimization during design. In this work, a set of equations was used to predict the compressive strength and elastic modulus of bone-like hydroxyapatite scaffolds produced by digital light processing-based vat photopolymerization (total porosity about 80 vol.%). The compressive strength was found to depend on total porosity, following a power-law approximation. The relationship between porosity and elastic modulus was well fitted by second-order power law, with relative density and computational models obtained by numerical simulations. Full article

Nowadays, humidity sensors are attracting a great deal of attention, and there are many studies focusing on enhancing their performances. Nevertheless, their fabrication through facile methods at reasonable cost is a significant factor. In this article, a new magnesium silicate nanopowder was successfully synthesized using a simple and low-cost sol–gel method. Subsequently, modified sepiolite was achieved by the substitution of iron ions in the synthesized nanopowders. The specimens were then characterized by X-ray diffraction, field emission–scanning electron microscopy, X-ray photoelectron spectroscopy, thermogravimetric–differential thermal analysis, infrared spectroscopy, and nitrogen adsorption. Furthermore, humidity sensors were manufactured by screen printing the prepared powders on alumina substrates with interdigitated Pt electrodes. The results showed that the fabricated sensors with modified sepiolite exhibited interesting characteristics for humidity detection. Full article

Mica is a group of clay minerals that are frequently used to fabricate electrical and thermal insulators and as adsorbents for the treatment of cationic pollutants. However, conventional subtractive manufacturing has the drawback of poor three-dimensional (3D) shape control, which limits its application. In this study, we propose digital light processing (DLP)-based additive manufacturing (AM) as one of the most effective ways to address this drawback. Two major challenges for the ceramic DLP process are the production of a homogeneous and stable slurry with the required rheological properties and the maintenance of printing precision. The mica green body was fabricated using a 53 vol.% solid loading slurry through DLP, which exhibited good dimensional resolution under an exposure energy dose of 10 mJ/cm². The precise, complex 3D structure was maintained without any defects after debinding and sintering at 1000 °C. The use of ceramic AM to overcome the shape-control limitations of mica demonstrated in this study offers great potential for expanding the applications of mica. Full article

The new approach to obtaining ceramic materials in the Na₂O–CaO–SiO₂–P₂O₅ system based on the binder—an aqueous solution of sodium silicate and filler—hydroxyapatite was shown in current research. After heat treatment at 500 °C and 700 °C, the ceramic samples included non-reacted hydroxyapatite Ca₁₀(PO₄)₆(OH)₂, β-rhenanite β-NaCaPO₄ and sodium calcium silicophosphate Na₂Ca₄(PO₄)₂SiO₄. An increase in temperature to 900 °C and 1100 °C allowed to obtain ceramic materials with the following phases: devitrite Na₂Ca₃Si₆O₁₆, β-rhenanite β-NaCaPO₄, β-wollastonite β-CaSiO₃, and silicon dioxide SiO₂. The strength of ceramic samples rose with increasing temperature from ≈7.0 MPa (bending) and ≈7.2 MPa (compression) at 500 °C to ≈9.5 MPa (bending) and ≈31.6 MPa (compression) at 1100 °C. At the same time, the apparent density decreased from 1.71 g/cm³ to 1.15 g/cm³. The top of the compressive strength equal to 31.6 MPa was observed when the apparent density was 1.15 g/cm³. Obtained ceramics consisted of biocompatible phases, widely studied in the literature; thus, it confirms the possibility of using an aqueous solution of sodium silicate in medical materials science. Full article

Y₂O₃ at 3% mol partially stabilized Zr₂O₃ (3YSZ) porous specimens with variable open porosity, from fully dense up to ~47%, and their potential use as anode supports for new solid oxide cell designs were fabricated by tape casting. The stiffness, strength and fracture properties were measured to investigate the influence of porosity on mechanical properties. The evolution of Young’s modulus and characteristic strength was evaluated by ball-on-ring tests. The variation of critical plane stress Mode I stress intensity factor with porosity has also been investigated and modelled from the results obtained from fracture mechanics testing. R-curve behaviour was observed in dense 3YSZ specimens and in porous 3YSZ compositions. The width of the transformation zone after fracture mechanics testing and the variation with porosity were investigated. The phases existing in the fracture zone were determined and quantified by Raman spectroscopy. It was found that the width of the transformation zone increased with increasing porosity. A new general R-curve model for 3YSZ based on the McMeeking–Evans equation is presented, which can be used to predict the behaviour of the R-curve as a function of porosity, simply by knowing the properties of the dense material and introducing in this equation porosity-dependent laws on the key properties that affect fracture toughness. Full article

Biocompatibility of ceramic materials in Ca₂P₂O₇-Ca(PO₃)₂ system was investigated using different methods, including in vitro and in vivo tests. Ceramic materials in the Ca₂P₂O₇-Ca(PO₃)₂ system were obtained by annealing cement-salt stone based on powder mixtures of calcium citrate tet-rahydrate Ca₃(C₆H₅O₇)₂·4H₂O and monocalcium phosphate monohydrate (MCPM) Ca(H₂PO₄)₂·H₂O. The phase composition of cement-salt stone included brushite, monetite as a result of chemical reaction of starting components after adding of water. The presence of citric acid as by-product of chemical reaction, leads to increase the setting time of the cement-salt stone. Highly concentrated aqueous suspensions based on calcium citrate and MCPM powders providing content of calcium polyphosphate Ca(PO₃)₂ up to 20 wt % in ceramics were used for designing bioresorbable materials. The presence of an excess of monocalcium phosphate monohydrate makes it possible to reduce the annealing temperature of ceramics, which is associated with the formation of a lower melting phase of Ca(PO₃)₂. In vivo tests shown that obtained ceramic materials can be recommended for regenerative treatments for bone defects. Full article

Fine powders of mixed gadolinium tantalum niobates doped with Eu, Sm, Tb, and Er were synthesized. Ceramic samples of polycomponent solid solutions of Gd_0.96Eu_0.01Sm_0.01Tb_0.01Er_0.01Nb_0.9Ta_0.1O₄ were obtained from synthesized powders using conventional sintering technology. The phase composition and phase structure characteristics of the Gd_0.96Eu_0.01Sm_0.01Tb_0.01Er_0.01Nb_0.9Ta_0.1O₄ ceramic phases were determined by XRD. The effect of ceramic sintering temperature on the physical characteristics of Gd_0.96Eu_0.01Sm_0.01Tb_0.01Er_0.01Nb_0.9Ta_0.1O₄ solid solutions is shown. The morphological features of the microstructure of the Gd_0.96Eu_0.01Sm_0.01Tb_0.01Er_0.01Nb_0.9Ta_0.1O₄ ceramics were studied in relation to its mechanical characteristics. At the same time, the strength characteristics (Young’s modulus, microhardness) and the critical stress intensity factor for mode I K_IC were evaluated for the first time for the synthesized compounds. Photoluminescence and cathodoluminescence were studied in the visible region. The study confirms the potential application of Gd_0.96Eu_0.01Sm_0.01Tb_0.01Er_0.01Nb_0.9Ta_0.1O₄ ceramic solid solutions as scintillators and radioluminescent light sources. Full article

A mixture of abramis brama (freshwater bream), carassius carassius (crucian carp), and sander lucioperca (pike perch) scales was used for the preparation of fish scale powder containing constituents of organic and inorganic nature. The mixture of the mentioned fish scales was washed, dried, and ground for the preparation of fish scale powder. Vibration sieving was used to prepare fish scale powder enriched with inorganic components. According to thermal analysis data, this fish scale powder enriched with inorganic components included about 36.5 wt.% components removed when heating, primarily those of organic nature, and 63.5 wt.% mineral components. Inorganic powders consisting of hydroxyapatite and magnesium whitlockite were obtained via heat treatment of this fish scale powder at 800–1000 °C. Particles of these inorganic powders consisted of sintered grains with dimensions less than 100 nm after heat treatment at 800 °C, less than 200 nm after heat treatment at 900 °C, and 100–1000 nm after heat treatment at 1000 °C. Fish scale powder enriched with inorganic components as well as heat-treated inorganic powders consisting of hydroxyapatite and magnesium whitlockite can be recommended for the production of different materials, such as ceramics or composites. Full article

Porous yttriastabilized zirconia (YSZ), in a composite with NiO, is widely used as a cermet electrode in solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs). Given cycles of high temperature in these energy devices, mechanical integrity of the porous YSZ is critical. Pore morphology, as well as properties of the ceramic, ultimately affect the mechanical properties of the cermet electrode. Here, we fabricated porous YSZ sheets via freezing of an aqueous slurry on a cold thermoelectric plate and quantified their flexural properties, both for as-fabricated samples and samples subjected to thermal shock at 200 °C to 500 °C. Results of this work have implications for the hydrogen economy and global decarbonization efforts, in particular for the manufacturing of SOFCs and SOECs. Full article

Polycrystalline zinc selenide (ZnSe) and Cr²⁺ or Fe²⁺ doped ZnSe are key optical elements in mid-infrared laser systems. The laser-induced damage of the optical elements is the limiting factor for increasing the power and pulse energy of the lasers. In the present work, the optical damage of the ZnSe, Cr²⁺:ZnSe, and Fe²⁺:ZnSe samples induced by a repetitively pulsed Ho³⁺:YAG laser at 2091 nm was studied. The probability of the optical damage and the laser-induced damage threshold (LIDT) were determined for the samples manufactured using different processing techniques. The highest LIDT was found in ZnSe samples annealed in an argon atmosphere. It was also found that the samples annealed in a zinc atmosphere or with hot isostatic pressing resulted in a decrease in the LIDT. The Cr²⁺-doped ZnSe had the lowest LIDT at 2.1 µm compared to Fe²⁺-doped or undoped ZnSe. The LIDT fluence of all tested ZnSe samples decreased with the increase in the pulse repetition rate and the exposure duration. The results obtained may be used to improve the treatment procedures of ZnSe, Cr²⁺:ZnSe, and Fe²⁺:ZnSe polycrystals to further increase their LIDT. Full article

The aim of this work is to study the hydrogenation processes in lithium-containing ceramics under high-temperature irradiation. Irradiation was carried out with protons with an energy of 1 MeV and fluences of 10¹⁵–10¹⁷ ion/cm² at irradiation temperatures of 300–1000 K. The choice of irradiation conditions is due to the possibility of simulation of the radiation damage accumulation processes in the near-surface layer of Li₂TiO₃ ceramics, as well as establishing the dependences of changes in structural parameters during temperature heating of samples during irradiation. It has been established that at irradiation fluences of 10¹⁵–10¹⁶ ion/cm², the formation of dislocation defects is observed, the density of which has a pronounced dependence on the irradiation temperature. At irradiation fluence above 5 × 10¹⁶ ion/cm², an increase in the crystal structure deformation is observed, due to swelling processes as a result of implanted hydrogen accumulation in the near-surface layer structure. At the same time, an increase in the irradiation temperature leads to a decrease in the swelling value, which is due to the accelerated migration of implanted hydrogen in the near-surface layer and its release through the existing pores. Results of mechanical tests showed that the swelling of the crystal structure and its deformation leads to embrittlement and a partial decrease in the strength of the near-surface layer. The obtained research results will further allow us to evaluate the resistance of lithium ceramics to the processes of hydrogenation and destruction as a result of the formation of gas-filled cavities in the structure of the near-surface layer. Full article

The influence of certain factors on the kinetics of the process of obtaining aluminum borides (burning rate, ingot formation, and phase separation) was investigated. In this study, we report the registration of diboride using the SHS protocol. The synthesis of aluminum diboride from boric anhydride occurred by the aluminothermic method. The initial components were boron trioxide and aluminum in the form of powders. Researchers paid special attention to the degree of grinding of the charge fluxing substances. The influence this had on the rate of development of the degree of charge concentration was studied. To calculate the degree of charge, a composition was chosen according to the speed obtained from a number of experiments where melting was carried out with the following charge densities in g/cm³: 0.80; 1.08; 1.18; 1.74. The method of melting was ignition from above. The experimental results allowed us to conclude that the nature of the change in the combustion rate of the system, where there was an excess of the reducing agent in the charge, is the same. An increase in the combustion rate, where there was an excess of aluminum of up to 20%, was likely due to the fact that the reaction area of the charge components increased. In addition, an increase in speed can be explained by a decrease in heat losses due to a reduction in the melting time. With an increase in excess aluminum above 20% of the stoichiometry, the observed decrease in the combustion rate can be explained by a decrease in the specific heat of the process due to the melting of the excess aluminum, which played the role of a ballast. Full article

Nanoscale powders of hydrated Ca₂P₂O₇, CaCO₃, and a product of mixed-anionic composition containing P₂O₇⁴⁻ and CO₃²⁻ anions were synthesized from aqueous solutions of Ca(CH₃COO)₂, pyrophosphoric acid (H₄P₂O₇), and/or (NH₄)₂CO₃. Pyrophosphoric acid was previously obtained on the basis of the ion exchange process from Na₄P₂O₇ solution and H⁺-cationite resin for further introduction into the reactions as an anionic precursor. The phase composition of powders after the syntheses was represented by bioresorbable phases of X-ray amorphous hydrated Ca₂P₂O₇ phase, calcite and vaterite polymorphs of CaCO₃. Based on synthesized powders, simple cylindrical constructions were prepared via mechanical pressing and fired in the temperature range of 600–800 °C. Surface morphology observation showed the presence of bimodal porosity with pore sizes up to 200 nm and 2 μm, which is likely to ensure tight particle packing and roughness of the sample surface required for the differentiation of osteogenic cells. Thus, the prepared ceramic samples can be further examined as model objects for bone tissue repair. Full article

Apatite is widely used in medicine as a biomaterial for bone tissue restoration. Properties of apatite depend on its composition, including the Ca/P ratio. This paper shows what range of Ca/P ratio can be attained in apatite by the mechanochemical method of synthesis, providing fast formation of a single-phase product. The synthesis was carried out from a reaction mixture of CaHPO₄ and CaO at different Ca/P ratios in the range of 1.17–2.10. The products were studied by PXRD, FTIR and NMR spectroscopy, HRTEM, and STA. In mixtures with a low initial Ca/P ratio (1.17–1.48), directly in the mill, the formation of calcium orthophosphate with whitlockite structure containing an HPO₄²⁻ group and structural water is shown for the first time. This phosphate has structure similar to that of whitlockites of hydrothermal origin and differs from high-temperature β-tricalcium phosphate that has composition Ca₃(PO₄)₃. A series of samples of apatite was obtained with varied composition, which depends on the initial Ca/P ratio. At Ca/P < 1.67, the formation of two types of calcium-deficient apatite was documented. At Ca/P > 1.67, the existence of two types of calcium-rich apatite is confirmed. Full article