Ceramic clays are among the most complicated of ceramic systems because of the very intricate relationship between the behavior of minerals during ceramic processing and their modifications during heating. A major challenge is to predict the phase changes in clay ceramics. The aims of this study were to establish reference data of ceramic products that can be formed based on the mineralogical compositions of the local raw materials. These data, in turn, can be compared with archeological ceramics in order to study their origins.

The mineralogical compositions and modifications during firing (550–1100°C under oxidizing conditions) of seven clayey materials sampled from the main clay deposits of northern Morocco were evaluated by X-ray powder diffraction. Two groups of clays were distinguished according to the type of neoformed high-temperature minerals: non-calcareous clays and calcareous clays. For the non-calcareous raw materials, spinel was produced at 950°C. Cristobalite and mullite were formed at temperatures in excess of 1000°C from clays that contain illite, kaolinite, and chlorite. In clays containing vermiculite and large amounts of chlorite, hematite was formed at temperatures in excess of 950°C. Firing of calcareous clays at temperatures >950°C yielded Ca-silicates (diopside, gehlenite and wollastonite), spinel, cristobalite, hematite, and feldspars. Mullite may also form in the calcareous clay products when the carbonate content exceeds 10%.

Red clay is considered to be of significant value to the economy in Morocco, particularly in the Safi region, because of its abundance. This raw material has long been known for its quality in the manufacture of clay materials, but its use was limited to traditional ceramics. The red clay raw material was the subject of the current study with the objective of opening new industrial applications that will give added value to the Safi red clay. The physicochemical, mineralogical, and thermal properties of the Moroccan red clay were determined by X-ray fluorescence (XRF), inductively coupled plasma-atomic emission spectroscopy (ICP-AES) analysis, X-ray diffraction (XRD), oriented aggregate, and particle-size analyses, powder density by helium pycnometry, carbonate content using the Bernard method, differential thermal analysis (TG–DTA), and the BET surface area. The compacted dry powder particles were calcined at three sintering temperatures: 900, 1000, and 1100°C for 2 h. The effect of sintering temperature on ceramic properties, such as apparent porosity, water adsorption, bulk density, and mechanical strength, was examined. Dense ceramics with lower porosity and greater mechanical resistance (~300%) were produced by increasing the sintering temperature from 900 to 1100°C. The conclusion was that the evolution of physicochemical and thermal properties is related to mineralogical changes, which show that anorthite is the major phase at higher temperatures.

This article examines the different mechanisms of the circulation of Chinese ceramics in the Middle East during the Abbasid-Chinese ceramic exchange during the eighth–tenth centuries ce. Although trade has been used conveniently to denote the circulation of Chinese wares in the Abbasid Caliphate, it is not the only mechanism that existed. There were also other possible processes of circulation, such as ceramics sent as tributes, diplomatic gifts, and samples, and secondary distribution through looting and pilgrimage. Not all Chinese wares shipped to the Middle East were luxury goods. Different types of Chinese wares had different functions and commercial and aesthetic values in the Middle East. It is an oversimplification to describe the circulation of Chinese wares in the Middle East as merely the result of the luxury goods trade.

The Bell Beaker site near Brodek u Prostějova (Czechia) has yielded remains of a large timber construction accompanied by four symmetrical ritual deposits with numerous artefacts, including more than fifty ceramic vessels. Their decoration consists of incised patterns, in nineteen cases with preserved white inlaid incrustations. To investigate the social relations at this extraordinary site, a multi-analytical and micro-destructive approach was employed to determine the provenance and technology of the pottery and the composition of the white incrustations. The results indicate various origins for the pottery within the region and the presence of extra-regional fabrics and graphitic temper. The main raw materials for the white inlays were calcium carbonate (calcite), hydroxyapatite (bone), and bright clay. The mixing of decorative motifs and the variation in the shape and size of the beakers suggest unique manufacturing processes. These results lend support to the monumental site of Brodek serving as a ritual place for several communities from both local and wider areas.

Na0.5Bi0.5TiO3-based ceramics have been paid great attention as Pb-free piezoelectric and electrical energy storage materials. Here, adding 10 mol% BiFeO3 in Na0.5Bi0.5TiO3–SrTiO3 binary system, 0.5Na0.5Bi0.5TiO3–0.4SrTiO3–0.1BiFeO3 ceramics were prepared by a conventional solid-state reaction method. Dielectric measurements reflected a near-plateau dielectric response at high temperature, e.g., the mid-dielectric permittivity of 2052 with the variation within ±10% from 57 to 371 °C and within ±15% from 54 to 371 °C for the ceramic sintered at 1100 °C. At a moderate electric field of 70 kV/cm, a capacitor made by the ceramic has an electrical energy storage density of 0.95 J/cm3, while the polarization has yet saturated at the moderate electric field. These results suggest that 0.5Na0.5Bi0.5TiO3–0.4SrTiO3–0.1BiFeO3 ceramic is a promising novel material with thermally stable dielectric permittivity and high electrical energy storage property for applications in high-temperature electronics.

The validity of Mn element on enhanced energy storage performance and fatigue resistance of Mn-doped 0.7Na0.5Bi0.5TiO3–0.3Sr0.7Bi0.2TiO3 lead-free ferroelectric ceramics (BNT–BST–xMn) is certified by doping. The effects of Mn modification on the dielectric behavior, ferroelectric, energy storage properties, and AC impedance are comprehensively investigated. It is found that the average grain size of the ceramics modified by Mn additions is reduced slightly. Moreover, the relaxor properties are evidently enhanced with the increased Mn content. The AC impedance spectra can even better clarify the dielectric response and relaxor behavior. The results suggest that both of the dielectric response and relaxor behavior are determined by defects especially concentration of the oxygen vacancy. The superior energy storage properties are realized at x = 0.05 with an energy storage density (Wrec) of 1.33 J/cm3 as well as energy storage efficiency (η) of 86.2% at 100 kV/cm, accompanied with a superior thermal stability. BNT–BST–5Mn ceramics can maintain a stable energy storage performance within 106 fatigue cycles, indicating an excellent fatigue resistance.

Sodium niobate (NaNbO3)-based dielectrics have received much attention for energy storage applications due to their low-cost, lightweight, and nontoxic nature. The field-induced metastable ferroelectric phase in NaNbO3-based dielectrics, however, leads to a large hysteresis of the polarization–electric field (P–E) loops and hence deteriorate the energy storage performance. In this study, the hysteresis was successfully reduced by introducing Bi3+ and Ti4+ into A-site and B-site of NaNbO3, respectively. MnO2 addition was added to further increase the ceramic density and enhance the cycling reliability. As a result, a high recoverable energy density of 4.3 J/cm3 and a high energy efficiency of 90% were simultaneously achieved in the ceramic capacitor at an applied electric field of 360 kV/cm. Of particular importance is that the ceramic capacitor exhibits a stable energy storage properties over a wide temperature range of −70 to 170 °C, with much improved electric cycling reliability up to 105 cycles.

The effects of CaTiO3 (CT) and BaZrO3 (BZ) modification upon the crystal structure and electromechanical properties of lead-free Bi0.5Na0.5TiO3–SrTiO3 piezoelectric ceramics were compared within a doping range of 0–4 mol%. The different effects of CT and BZ modification upon the phase transition are clearly observed in the polarization and strain hysteresis loops. The CT-modified specimens maintain strong ferroelectricity without any abnormal enhancement in the electric field-induced strain. However, the addition of as little as 1 mol% BZ induces a transition from a nonergodic relaxor phase to an ergodic relaxor phase, thus resulting in disruption of the ferroelectric order and the generation of a high field-induced strain. The present authors believe that the substitution of large ions (such as Zr4+) into the B-sites, rather than the A-sites, of the Bi0.5Na0.5TiO3-based ceramics plays a significant role in the phase transition behavior.

Potassium and cerium co-doped Bi4Ti2.86W0.14O12 ceramics with a formula of (K0.5Ce0.5)xBi4−xTi2.86W0.14O12 (abbreviated as KC100x-BITW, x = 0, 0.02, 0.04, 0.06, 0.08, 0.1) were prepared by a conventional solid-state reaction method. The effect of (K0.5Ce0.5) complex doping amount on the structure, dielectric, and piezoelectric properties of the KC100x-BITW ceramics was investigated. X-ray diffraction results indicated that the KC100x-BITW ceramics are Aurivillius-type phase with the bismuth layer structure. (K0.5Ce0.5) complex addition first increases and then decreases the grain size which can be observed by scanning electron microscopy. With the increase of (K0.5Ce0.5) complex doping amount, the Curie temperature (TC) was slightly decreased from 632 to 608 oC. The dielectric and piezoelectric properties were optimized in KC100x-BITW ceramics with x = 0.08 as follows: d33 = 24 pC/N, kp = 8.2%, Qm = 6766, εr = 135 (@100 kHz), tanδ = 0.28% (@100 kHz), Tc = 611 oC, and resistivity ρ = 2.9 × 106 Ω cm at 500 oC, indicating that the KC100x-BITW ceramics are suitable for high-temperature piezoelectric sensing applications.

The mitigation of CMAS (calcium–magnesium–aluminum–silicon oxide) infiltration is a major requirement for the stability of thermal barrier coatings. In this study, yttria-stabilized zirconia (YSZ)–Al2O3–SiC, YSZ–Al2O3–Ta2O5, and YSZ–Al2O3–Nb2O5 self-healing composites produced by uniaxially pressing powders were investigated as an alternative to YSZ. CMAS infiltration in these materials was tested at 1250 °C for 10 h. Comparing the depth of CMAS infiltration using scanning electron microscope (SEM) in tandem with electron-dispersive X-ray spectroscopy (EDS), all self-healing materials were found to perform better than the reference materials. While standard YSZ shows massive CMAS infiltration, SEM micrographs and EDS maps revealed a 33-fold improvement in CMAS resistance for the YSZ–Al2O3–Nb2O5 system, which exhibited the best performance among the selected self-repairing materials. X-ray diffraction and high-resolution SEM micrographs taken 10 μm below the surface revealed that CMAS only infiltrated pores in the topmost region of the samples. Both YSZ–Al2O3–Ta2O5 and YSZ–Al2O3–Nb2O5 systems showed no signs of chemical reaction with CMAS.

Calcium–magnesium–alumino-silicate (CMAS) reaction and infiltration behavior were studied in phase pure and mixed phase ytterbium silicate environmental-barrier coating (EBC) materials at 1300 °C. Phase pure Yb2Si2O7 (YbDS) was infiltrated by CMAS via grain boundaries/pores, resulting in loss of its structural integrity. Phase pure Yb2SiO5 (YbMS) reacted with CMAS to form either apatite (Ca2Yb8(SiO4)6O2) or YbDS, depending on the initial glass composition. Both reactions in YbMS slowed infiltration kinetics considerably compared to YbDS. Samples having a YbDS matrix with controlled amounts and dispersions of YbMS were also investigated as a model for air plasma spray coatings. Samples containing ≥20 vol% coarse YbMS showed dramatically improved infiltration behavior compared to phase pure YbDS. YbDS samples containing a fine dispersion of YbMS displayed a new mode of CMAS attack in which glass spread on the sample surfaces. The results of this study suggest that EBC phase compositions and microstructures may be tailored for optimized CMAS resistance.

Cerium-doped lanthanum magnesium bulk aluminate (La1–xCexMgAl11O19, x = 0.03–0.50; abbreviated as LMA) was prepared via the Pechini sol–gel method after heating at 1200 °C for 2 h. The resulting single-phase ceramics was studied in terms of its structure using X-ray diffraction and optical properties using photoluminescence, its decay time, and radioluminescence spectroscopy. The diffraction and electron microscopy demonstrated LMA's plate-shaped nanocrystals with structure anisotropy and relatively broad particle size distribution. The optical measurements fully manifested the complexity of the LMA crystal structure. The radioluminescence study of cerium-doped LMA is here presented for the first time and, thus, contributes to the basic knowledge of Ce-doped materials. Additionally, the magnetic susceptibility exhibiting paramagnetic behavior of Ce3+ ions is presented. The magnetic data were interpreted in terms of local atomic Hamiltonian involving the crystal field and the Zeeman effect applied on the ground state J = 5/2 multiplet.

High-temperature (1500 °C) interactions of promising environmental-barrier coating (EBC) ceramics in the rare-earth (RE) pyrosilicate system, Yb(2-x)YxSi2O7 (x = 0, 0.2, 1, or 2), with three different calcia–magnesia–aluminosiliate (CMAS) glass compositions, are explored. Only the Ca/Si ratio is varied in the CMAS: 0.76, 0.44, or 0.10. Interaction between the highest Ca/Si CMAS and the EBC ceramic with the lowest x (=0, Yb2Si2O7) promotes no reaction but the formation of “blister” cracks. In contrast, the highest x (=2, Y2Si2O7) promotes the formation of an apatite reaction product, but no “blister” cracks. Observationally, it is found that a decrease in the CMAS Ca/Si ratio (0.76–0.10) and a decrease in Y-content decreases the propensity for reaction crystallization (apatite formation) and “blister” cracks. These results are rationalized based on the relative affinities between Ca2+ in the CMAS and Y3+ or Yb3+ in the EBC ceramics, suggesting a way to tune the CMAS interactions in RE pyrosilicate solid solutions.

Here, we develop and characterize high thermal conductivity/high thermal shock-resistant bulk Ce-doped Al2O3 and propose it as a new phosphor converting capping layer for high-powered/high-brightness solid-state white lighting (SSWL). The bulk, dense Ce:Al2O3 ceramics have a 0.5 at.% Ce:Al concentration (significantly higher than the equilibrium solubility limit) and were produced using a simultaneous solid-state reactive current activated pressure-assisted densification (CAPAD) approach. Ce:Al2O3 exhibits a broadband emission from 400 to 600 nm, which encompasses the entire blue and green portions of the visible spectrum when pumped with ultraviolet (UV) light that is now commercially available in UV light–emitting devices and laser diodes (LD). These broadband phosphors can be used in the commonly used scheme of mixing with other UV-converting capping layers that emit red light to produce white light. Alternatively, they can be used in a novel composite down-converter approach that ensures improved thermal–mechanical properties of the converting phosphor capping layer. In this configuration, Ce:Al2O3 is used with proven phosphor conversion materials such as Ce:YAG as an active encapsulant or as a capping layer to produce SSWL with an improved bandwidth in the blue portion of the visible spectrum. To study the effect of crystallinity on the Ce photoluminescent (PL) emission, we synthesize Ce:YAG ceramics using high-pressure CAPAD at moderate temperatures to obtain varying crystallinity (amorphous through fully crystalline). We investigate the PL characteristics of Ce:Al2O3 and Ce:YAG from 295 to 4 K, revealing unique crystal field effects from the matrix on the Ce dopants. The unique PL properties in conjunction with the superior thermal–mechanical properties of Ce:Al2O3 can be used in high-powered/high-brightness–integrated devices based on high-efficiency UV-LD that do not suffer efficiency droop at high drive currents to pump the solid-state capping phosphors.

Nuclear fuel debris generated at the Fukushima Daiichi nuclear power plant during the loss of coolant accident in 2011, still resides within the reactor units, constantly cooled by water. Until it is retrieved, the fuel debris will corrode, releasing radioactive elements into the coolant water and the ground surrounding the reactors. To predict the corrosion behaviour of these materials, and to establish parameters for experiments with U-containing and real fuel debris, the corrosion of two surrogate fuel debris materials, with a composition of Ce(1-x)ZrxO2 (x = 0.2 and 0.4), was investigated. Materials were synthesised by a wet chemistry route and pellets were sintered at 1700°C in air atmosphere. Due to the slow corrosion kinetics, aggressive conditions were applied, and corrosion experiments were performed in 9 mol.L-1 HNO3 under static conditions. The incorporation of Zr into the structure of Ce reduced the normalised dissolution rate; from (3.75 ± 0.15) × 10-6 g.m-2.d-1 to (4.96 ± 0.28) × 10-6 g.m-2.d-1 for RL(Ce) of Ce0.8Zr0.2O2 and Ce0.6Zr0.4O2, respectively.

Computational modeling is an important aspect of the research on nuclear waste materials. In particular, atomistic simulations, when used complementary to experimental efforts, contribute to the scientific basis of safety case for nuclear waste repositories. Here we discuss the state-of-the-art and perspectives of atomistic modeling for nuclear waste management on a few cases of successful synergy of atomistic simulations and experiments. In particular, we discuss here: (1) the potential of atomistic simulations to investigate the uranium oxidation state in mixed-valence uranium oxides and (2) the ability of cementitious barrier materials to retain radionuclides such as 226Ra and 90Sr, and of studtite/metastudtite secondary peroxide phases to incorporate actinides such as Np and Am. The new contribution we make here is the computation of the incorporation of Sr by C-S-H (calcium silicate hydrate) phases.

Immobilisation of Pu in a zirconolite matrix (CaZrTi2O7) is a viable pathway to disposition. A-site substitution, in which Pu4+ is accommodated into the Ca2+ site in zirconolite, coupled with sufficient trivalent M3+/Ti4+ substitution (where M3+ = Fe, Al, Cr), has been systematically evaluated using Ce4+ as a structural analogue for Pu4+. A broadly similar phase assemblage of zirconolite-2M and minor perovskite was observed when targeting low levels of Ce incorporation. As the targeted Ce fraction was elevated, secondary phase formation was influenced by choice of M3+ species. Co-incorporation of Ce/Fe resulted in the stabilisation of a minor Ce-containing perovskite phase at high wasteloading, whereas considerable phase segregation was observed for Cr3+ incorporation. The most favourable substitution approach appeared to be achieved with the use of Al3+, as no perovskite or free CeO2 was observed. However, high temperature treatments of Al containing specimens resulted in the formation of a secondary Ce-containing hibonite phase.

Improved budgeting of heat loads arising from radiogenic heating in high level wastes (HLW) could allow enhanced usage of geological disposal facility space. Separation of high heat generating nuclides from HLW, such as Cs, would simplify management of heat loads. A potential host matrix for Cs-disposal is hollandite. The incorporation of Cs into the hollandite phase is aided by substitution of cations on the B-site of the structure; these ions may include Ni and Zn. Two series of hollandites, Ni-substituted and Zn-substituted, were synthesised via an alkoxide-nitrate route and consolidated by cold uniaxial pressing and sintering or by hot isostatic pressing. Characterisation of the resultant material by X-ray diffraction and scanning electron microscopy found that hollandite was formed for all levels of substitution. Materials produced via HIP were found to be denser indicating lower Cs loss. HIPed Ni hollandites were found to contain fewer secondary phases and it was concluded that they were the most suitable candidates

Residual stress can considerably weaken systems with ceramics-to-metal joints. Herein, we investigate the dependence of bonding strength and residual stress variation of a ceramics-to-metal joint system on the interface wedge angle and bonding temperature condition. First, disparity between large-scale displacement models with varying work-hardening parameters was confirmed using thermal elastoplastic Finite Element Method (FEM) analysis. Each interface wedge shape was set to a plane surface to compare FEM results to experimental results related to the effect of the interface wedge angle on the practical bonding strength. The experimental results were specifically for a system consisting of Si3N4-WC/TiC/TaC bonded to Ni plate. The effects of the wedge angle of the metal side on residual stress near the interface edge were numerically predicted using FEM models. The interface wedge angles for this model, φ1 and φ2, were defined using the configuration angle between the interface and free surfaces of both materials. The numerical results showed that the stress σr on the free surface of the ceramic side was concentrated near the interface edge at which discontinuity in the stress state is generated. Dependence of the residual stress variation on both the wedge angle and temperature conditions can be predicted. It was confirmed that the bonding strength improves with decreasing residual stress in geometrical conditions. Therefore, residual stress appears to be a predominant factor affecting bonding strength. The observed fracture pattern showed that the fracture originated near the interface edges, after which small cracks propagated on the ceramic side. The residual stress is presumed to dominate bonding strength as the fracture occurred near the interface edge of the ceramic side. Results showed that the maximum bonding strength appears at the geometrical condition where the fracture pattern changes to φ2 lower than 90° of joint bonded at 980 °C. Therefore, the optimum interface wedge angle depends on a combination of materials and bonding temperature conditions, because the weak point of the bonded joint system will affect the stiffness balance of both materials and the adhesion power of the bonded interface.