Humidity Related Low Temperature Conductivity Hysteresis of Ce1–xZrxO2 (0 ≤ x ≤ 1) Ceramics. Structural Disorder Relationship

Ion‐electron mixed conductivity of the Ce_1–xZr_xO₂ (0 < x < 1) series, prepared by solid‐state reaction, has been measured as a function of temperature, pO₂ and pH₂O relative pressures. The structural analysis of this series shows the formation of monoclinic, tetragonal, and cubic phases as the Ce content increases. The temperature used in samples preparation, 1,923 K, favors at intermediate compositions the homogeneous Ce and Zr mixing in the metastable tetragonal t′ phase. The variation of conductivity with the relative oxygen pressure indicates that electronic contribution increases, becoming preponderant, as the Ce‐content increases. The modifications in conductivity observed in Ce‐rich samples have been ascribed to the enhancement of the electronic contribution at the grain‐boundary of ceramics. The differences observed at low temperatures in electronic dc‐conductivity of Ce‐rich samples during heating and cooling treatments, have been ascribed to the incorporation of water as hydroxide defects at the grain boundary and interior of the particles. The surface hydroxylation is maximal in samples with improved OSC capacity, decreasing drastically in samples heated at 740 K. Finally, the potential application of prepared materials in intermediate temperature solid oxide fuel cells (SOFC) is discussed.     

Effect of phase evolution and acidity on the chemical stability of Zr1-xNdxSiO4-x/2 ceramics

Zircon ceramics (ZrSiO₄) are promising candidates for actinide immobilization. Here, a series of Zr_1-xNd_xSiO_4-x/2 (x?=?0, 0.02, 0.20, and 1.0) ceramics are prepared to study the effects of phase evolution and acidity on the chemical durability of ZrSiO₄-based nuclear waste forms. The results show that the chemical stability of the single-phase ZrSiO₄ sample is better than that of the biphasic Zr_0.8Nd_0.2SiO_3.9 sample due to the existence of a secondary highly soluble phase (Nd₂Si₂O₇), which increases the contact area with leachate. The normalized release rates of both zirconium (Zr) and neodymium (Nd) in the Zr_1-xNd_xSiO_4-x/2 ceramic waste forms increase with increasing Nd loading and acid concentration. LR_Zr in ZrSiO₄ ceramics and LR_Nd in Zr_0.98Nd_0.02SiO_3.99 ceramics are the lowest, while LR_Zr and LR_Nd reach the highest values in the Zr_0.8Nd_0.2SiO_3.9 and Nd₂Si₂O₇ ceramics, respectively. The normalized release rates of Zr are lower than those of Nd due to the difference in the energies of their bonds with oxygen atoms. Moreover, the changes in the surfaces of the leached ceramics are consistent with their leaching results.     

Structure and Microwave Dielectric Behavior of A‐Site‐Doped Sr(1−1.5x)CexTiO3 Ceramics System

The ion valence state, phase composition, microstructure, and microwave dielectric properties of Sr_(1?1.5x)Ce_xTiO₃ (x = 0.1–0.67, SCT) ceramics were systematically investigated. Sr_(1?1.5x)Ce_xTiO₃ ceramics were produced with gradual structural evolution from a cubic to a tetragonal and turned to an orthorhombic structure in the range of 0.1 ≤ x ≤ 0.67. Above a critical Ce proportion (x = 0.4), microstructural changes and normal grain growth initially occurred. On the basis of chemical analysis results, the reduction of Ti⁴⁺ ions was hastened by tetravalent ions (Ce⁴⁺). By contrast, this reduction was inhibited by trivalent ions (Ce³⁺). The observed dielectric behavior was strongly influenced by phase composition, oxygen vacancies (), and defect dipoles, namely, () and (). Temperature stable ceramics sintered at 1350°C for 3 h in air yielded an intermediate value of dielectric constant (ε_r = 40), with the smallest reported value of temperature coefficient of resonant frequency (τ_f = +0.9 ppm/°C), and quality factor (Q × f = 5699 GHz) at x = 0.6.     

Tunable negative thermal expansion and structural evolution in antiperovskite Mn3Ga1−xGexN (0 ≤ x ≤ 1.0)

The negative thermal expansion (NTE) and structural evolution of antiperovskite compounds Mn₃Ga_1?xGe_xN (0 ≤ x ≤ 1.0) were systematically investigated. Our results indicate the crystal structure of Mn₃Ga_1?xGe_xN changes from cubic (C) to tetragonal (T₄) with increasing Ge content by X‐ray diffraction (XRD).The negative thermal expansion from x = 0 (operation‐temperature range ?T = 20 K) to x = 0.4 (?T = 60 K) becomes broad and shifts to higher temperature, and then it became positive from x = 0.5 in Mn₃Ga_1?xGe_xN. Typically, Mn₃Ga_0.5Ge_0.5N shows low thermal expansion behavior between 300 and 450 K (?T = 150 K), and thermal expansion coefficient α is estimated to be 2 × 10^?6 K^?1. Furthermore, variable temperature XRD was measured to reveal the origin of NTE. The cubic I ‐ cubic II phases coexistence (x = 0.2) and cubic I ‐ tetragonal coexistence (x = 0.5, 0.6) was observed at low temperature. The tunable NTE is highly valuable for practical applications in precision devices.     

Preparation and characterization of powellite ceramics Ca1-xLix/2Cex/2MoO4 (0 ≤ x ≤ 1) for Mo-rich HLW condition

Powellite ceramic represent one candidate to immobilize minor actinides and Mo from reprocessed UMo nuclear fuel. In this work, the Ca_1-xLi_x/2Ce_x/2MoO₄ (0 ≤ x ≤ 1) series is prepared via a solid-state reaction using Ce³⁺ as trivalent minor actinide (Am³⁺) surrogate, with structure/microstructure characterized by XRD, XPS, HRTEM, and SEM as well. The Ca_1-xLi_x/2Ce_x/2MoO₄ (0 ≤ x ≤ 1) compositions crystallize in tetragonal and are isostructural with scheelite. Rietveld refinements show that Ce³⁺ and Li⁺ simultaneously enter into the eight-fold coordinated Ca site of powellite crystal. The chemical durability of powellite phases is evaluated by the ASTM C1285-14 product consistency test method B. The leaching behaviours of Ce and Mo are accordance with the interfacial dissolution-reprecipitation mechanism. For all the Ca_1-xLi_x/2Ce_x/2MoO₄ (0 ≤ x ≤ 1) ceramics, 7-days NL_Ce and NL_Mo are found to be in the order of 10⁻³-10⁻⁵ g·m⁻² and 10⁻²-10⁻⁴ g·m⁻² respectively, which exhibit the great retention of Ce and Mo. Interestingly, the values of 7-days NL_Ce and NL_Mo are predominantly controlled by the distortion of MoO₄ tetrahedra and disordered arrangements of Ce³⁺ and Li⁺. Thus, our initial understanding on the structure and chemical durability relation will provide insight to design new waste forms for the Mo-rich HLW condition.     

Rapid preparation of Gd2Zr2−xCexO7 waste forms by flash sintering and their chemical durability

A simple and low-energy-consuming approach for preparing ceramic nuclear waste forms is greatly preferred for disposal of ever-increasing amounts of radioactive nuclear wastes. Herein, simulated radionuclide Ce could be rapidly incorporated into Gd₂Zr₂O₇ ceramic via flash sintering technique. Under an electric field of 250 V/cm, Gd₂Zr_2−xCe_xO₇ (0.0 ≤x ≤ 1.2) waste forms with a single phase of defect-fluorite were flash sintered at relatively low temperatures of 889–997 °C in 60 s. The onset temperature of flash sintering was decreased with the enhancement of Ce content. Furthermore, the density and grain size of Gd₂Zr_2−xCe_xO₇ waste forms were increased with the increase of the current limit. The nearly full dense Gd₂Zr_2−xCe_xO₇ waste forms were flash sintered at a current limit of 200 mA. The normalized leaching rates of Gd, Ce, and Zr in Gd₂Zr_0.8Ce_1.2O₇ after 28 d were 6.5475 × 10⁻⁵, 1.1624 × 10⁻⁷, and 1.1613 × 10⁻⁷ g·m⁻²·d⁻¹, respectively, which exhibited a good chemical durability.     

The Effects of P-Poisoning of CexZr1−xO2 on the Transient Oxygen Storage and Release Kinetics

The present work reports on the investigation of the effects of chemical poisoning of Ce_xZr_1?xO₂ solids by phosphorous (P) on the kinetics of oxygen storage and release (OSR) of the thus derived P-contaminated solids, as a function of Ce_xZr_1?xO₂ solid composition (x = 0.3, 0.5 and 0.7) for the first time. Phosphorous deposition on the surface of Ce_xZr_1?xO₂ particles followed by calcination in air at 850 °C forms nano-crystals of CePO₄, which lead to a drastic decrease in the population of surface and subsurface reactive and mobile oxygen species due to the formation of P–O–Ce bonding. The concentration (μmol/g) of exchangeable ¹⁶O in the solid with ¹⁸O from the gas phase was found to increase, and the degree of reduction in the Oxygen Storage Capacity (OSC) to decrease with increasing Ce content in the Ce_xZr_1?xO₂ solid after P-poisoning. The increase in the Ce content of Ce_xZr_1?xO₂ makes its OSR properties more resistant against P-poisoning due to the increasing number of poison-free Ce atoms, which are able to participate in the Ce³⁺ ? Ce⁴⁺ redox cycle.     

Electrical Conductivity Improvement of Nd2Ce2O7 Ceramic Co‐doped with Gd2O3 and ZrO2

(Nd_1–xGd_x)₂(Ce_1–xZr_x)₂O₇ (0 ≤ x ≤ 0.5) ceramic powders synthesised by the chemical‐coprecipitation and calcination method were pressureless‐sintered at 1,973 K for 10 h in air. The structure and electrical conductivity of (Nd_1–xGd_x)₂(Ce_1–xZr_x)₂O₇ ceramics were investigated by the X‐ray diffraction and impedance spectroscopy measurements. (Nd_1–xGd_x)₂(Ce_1–xZr_x)₂O₇ (0 ≤ x ≤ 0.5) ceramics exhibit a single phase of defect fluorite‐type structure. The electrical conductivity of (Nd_1–xGd_x)₂(Ce_1–xZr_x)₂O₇ ceramics increases with temperature in the range 623–1,173 K following an Arrhenius law. At identical temperature levels, the measured electrical conductivity of (Nd_1–xGd_x)₂(Ce_1–xZr_x)₂O₇ ceramics varies with doping different Gd₂O₃ and ZrO₂ contents and exhibits a maximum at x = 0.1.     

Synthesis and Electrical Properties of New Lead‐free (100−x)(Li0.12Na0.88)NbO3–xBaTiO3 (0 ≤ x ≤ 40) Piezoelectric Ceramics

New lead‐free (100?x)Li_0.12Na_0.88NbO₃‐xBaTiO₃ (0 ≤ x ≤ 40) piezoelectric ceramics have been synthesized using conventional ceramics processing route. Structural analysis revealed an existence of morphotropic phase boundary (MPB), separating orthorhombic and tetragonal phases, between the BaTiO₃ content, x = 10–12.5. A partial phase diagram has been established based on temperature‐dependent permittivity data for this new system and a almost vertical temperature‐independent MPB is observed. Improvement in electrical properties near MPB (e.g., for x = 12.5; ε_r = 8842 at T_m and 795 at room temperature, d₃₃ = 30 pC/N, k_p = 12.0%, Q_m = 162, P_r = 11.2 μC/cm², E_c = 19.2 kV/cm, = 174 pm/V) is observed, and is attributed to the ease of polarization rotation due to coexistence of orthorhombic and tetragonal phases. The results show that these materials could be suitable for piezoelectric vibrators and ultrasonic transducer applications. The sample with x = 25, also exhibited high dielectric permittivity, ε_r = 2400, and low dielectric loss, tanδ = 0.033 at room temperature which could be suitable for capacitor (X7R/Z5U) applications.     

The NbO6 octahedral distortion and phase structural transition of Eu3+‐doped K0.5Na0.5NbO3–xLiNbO3 ferroelectric ceramics

A small quantity of Eu³⁺ ions were doped in the lead‐free ferroelectric K_0.5Na_0.5NbO₃–xLiNbO₃ (KNN–xLN, 0 ≤ x ≤ 0.08) ceramics to investigate the NbO₆ octahedral distortion induced by the increasing LN content. In addition, the phase structure, ferroelectric, and photoluminescence properties of K_0.5Na_0.5NbO₃–xLiNbO₃:0.006Eu³⁺ (KNN–xLN:0.006Eu³⁺) lead‐free piezoelectric ceramics were characterized. All the X‐ray diffraction, Raman spectra, dielectric constant vs temperature measurements and the photoluminescence of Eu³⁺ ions demonstrated that the prepared ceramics undergo a polymorphic phase transition (PPT, from orthorhombic to tetragonal phase transformation) with the rising LN content, and the PPT region locates at 0.05 ≤ x ≤ 0.06. The ferroelectric properties, Raman intensity ratios and photoluminescence intensity ratios show similar variations with the increasing LN content, all with a maximum value achieved at the PPT region. We believe that the close relationship among the ferroelectric properties, Raman intensity ratios, and photoluminescence intensity ratios is caused by the NbO₆ octahedral distortion. The photoluminescence of Eu³⁺ ion was discussed basing on the crystal‐symmetry principle and Judd‐Ofelt theory.     

The influence of phase transition on electrocaloric effect in lead‐free (Ba0.9Ca0.1)(Ti1−xZrx)O3 ceramics

In this paper, the influence of phase evolution on polarization change and electrocaloric response in lead‐free (Ba_0.9Ca_0.1)(Ti_1?xZr_x)O₃ ceramics (BCTZ) was systematically investigated. With increasing Zr/Ti ratio, the phase structure and phase transition behavior were greatly changed, resulting in various temperature and electric field dependence of electrocaloric responses. For x=0.05, a peak electrocaloric temperature change 1.64 K (at 130°C) and corresponding entropy change 1.78 J·kg^?1·K^?1 were obtained for 0‐7 kV·mm^?1 electric field. Negative electrocaloric temperature change in ?0.1 K was obtained below Curie temperature (T_c), which may be induced by the orthorhombic‐tetragonal ferroelectric phase transition. With the increase in x, the peak value of the electrocaloric response decreased but much better temperature stability was observed. Simultaneously the negative electrocaloric response gradually disappeared with the disappearance of the low temperature ferroelectric‐ferroelectric phase transition. For x=0.2, electrocaloric response showed good temperature stability ranging from room temperature to 130°C, attributing to the relaxor ferroelectric feature.     

Physical Properties of La1−xEuxPO4,0 ≤ x ≤ 1, Monazite‐Type Ceramics

Synthetic La_1?xEu_xPO₄ monazite‐type ceramics with 0 ≤ x ≤ 1 have been characterized by ultrasound techniques, dilatometry, and micro‐calorimetry. The coefficients of thermal expansion and the elastic properties are, to a good approximation, linearly dependent on the europium concentration. Elastic stiffness coefficients range from 182(1) to 202(1) GPa for c₁₁ and from 53.8(7) to 61.1(4) GPa for c₄₄. They are strongly dependent on the density of the sample. The coefficient of thermal expansion at 673 K is 8.4(3)  × 10^?6 K^?1 for LaPO₄ and 9.9(3)  × 10^?6 K^?1 for EuPO₄, respectively. The heat capacities at ambient temperature are between 101.6(8) J·(mol·K)^?1 for LaPO₄ and 110.1(8) J·(mol·K)^?1 for EuPO₄. The difference between the heat capacity of LaPO₄ and the Eu‐containing solid solutions is dominated by electronic transitions of the 4f‐electrons at temperatures above 75 K.     

Orthorhombic‐pseudocubic phase transition and piezoelectric properties of (Na0.5K0.5)(Nb1−xSbx)‐SrZrO3 ceramics

0.96(Na_0.5K_0.5)(Nb_1?xSb_x)‐0.04SrZrO₃ ceramics with 0.0≤x≤0.06 were well sintered at 1060°C for 6 hours without a secondary phase. Orthorhombic‐tetragonal transition temperature (T_O‐T) and Curie temperature (T_C) decreased with the addition of Sb₂O₅. The decrease in T_C was considerable compared to that in T_O‐T, and thus the tetragonal phase zone disappeared when x exceeded 0.03. Therefore, a broad peak for orthorhombic‐pseudocubic transition as opposed to that for orthorhombic‐tetragonal transition appeared at 115°C‐78.2°C for specimens with 0.04≤x≤0.06. An orthorhombic structure was observed for specimens with x≤0.03. However, the polymorphic phase boundary structure containing orthorhombic and pseudocubic structures was formed for the specimens 0.04≤x≤0.06. Furthermore, a specimen with x=0.055 exhibited a large piezoelectric strain constant of 325 pC/N, indicating that the coexistence of orthorhombic and pseudocubic structures could improve the piezoelectric properties of (Na_0.5K_0.5)NbO₃‐based lead‐free piezoelectric ceramics.     

Effects of Nd Content on Structure and Chemical Durability of Zirconolite–Barium Borosilicate Glass‐Ceramics

The effects of Nd₂O₃ content (0–12 wt %) on crystalline phases, microstructure, and chemical durability of barium borosilicate glass‐ceramics belonging to SiO₂–B₂O₃–Na₂O–BaO–CaO–TiO₂–ZrO₂–Nd₂O₃ system were studied. The results show that the glass‐ceramics with 2–6 wt% of Nd₂O₃ possess mainly zirconolite and titanite phases along with a small amount baddeleyite phase in the bulk. Calcium titanate appears when the Nd₂O₃ content increases to 8 wt%, and the amount of quadrate calcium titanate crystals increases with further increasing content of Nd₂O₃. For the glass‐ceramics with 6 wt% Nd₂O₃ (Nd‐6), Nd elements homogeneously distribute in zirconolite, titanite, and residual glass phases. There is a strong enrichment of Nd in calcium titanate crystals for the sample with 10 wt% Nd₂O₃. The viscosity of Nd‐6 glass is about 49 dPa·s at 1150°C. Moreover, Nd‐6 glass‐ceramics show the lower normalized leaching rates of B (LR_B), Ca (LR_Ca), and Nd (LR_Nd) when compared to that of the sample with 8 wt% Nd₂O₃. After 42 days, LR_B, LR_Ca, and LR_Nd of the Nd‐6 glass‐ceramics are about 6.8 × 10^?3, 1.6 × 10^?3, and 4.4 × 10^?6 g·m^?2·d^?1, respectively.     

Crystal distortion and electrical properties of Ce-doped BIT-based piezoelectric ceramics

Cerium (Ce)-modified Bi₄Ti_2.94W_0.03Ta_0.03O₁₂ (BITWT) high Curie temperature ceramics (abbreviated as BITWT-xCe) were fabricated by a conventional solid-state sintering method. All BITWT-xCe ceramics had an orthogonal phase, but the structural distortion of the Ce-doped BITWT ceramics was higher than that of BITWT ceramics, which reduced symmetry and improved piezoelectric performance. The relative density (ρ_r) of BITWT-xCe ceramics was greater than 97%. Under the same conditions, the hysteresis loop of BITWT-0.04Ce ceramics had higher saturation than that of BITWT ceramics. The piezoelectric constant (d₃₃) was enhanced, and the highest d₃₃ of 24.7 pC/N at x = 0.04 was obtained, which was 25% higher than that of BITWT ceramics (d₃₃ = 19.8 pC/N). In addition, the tentative conduction mechanism of BITWT-xCe ceramics was also discussed. Two oxidations (Ce³⁺ and Ce⁴⁺) were present in the Ce-doped BITWT ceramics.     

Effects of Ti-substitution on the crystal structures,micro-structures and microwave dielectric properties of Li2Mg3Zr1-xTixO6 (0 ≤ x ≤ 1) ceramics

Li₂Mg₃Zr_1?xTi_xO₆ (x = 0, 0.2, 0.4, 0.6, 0.8, 1) ceramics were prepared via a solid-state reaction method. Crystal structures, sintering behaviors, micro-structures and microwave dielectric properties of Li₂Mg₃Zr_1?xTi_xO₆ (0 ≤ x ≤ 1) ceramics were investigated by XRD, SEM and chemical bond theory. XRD results showed that a single phase with the rock-salt structure was formed in all ranges. On the basis of the Rietveld refinement and chemical bond theory, several intrinsic parameters were calculated and connections between intrinsic parameters and microwave dielectric properties were investigated. The substitutions of Ti⁴⁺ for Zr⁴⁺ obviously increased the relative density and improved the quality factors. Variations of ε_r could be explained by changes of the polarizability. Q·f values showed the similar trend with the packing fractions, average bond valences and lattice energy of Zr–O bonds. τ_? values significantly correlated with the bond energy of Zr–O bonds.     

The structure,sintering process,and chemical durability of Ce0.5Gd0.5PO4 ceramics

In this work, Ce_0.5Gd_0.5PO₄ was designed by first principles calculations to investigate the effect of 50% doped Gd on its structural properties. The Ce_0.5Gd_0.5PO₄ ceramics were then prepared via hot-press sintering (HPS) and pressureless sintering (PLS). Their chemical durability was studied to evaluate the leaching resistance of Ce and Gd under leachates along with an examination of the effect of sintering on chemical durability. The results show that the local-density approximation (LDA) plus Hubbard energy (U) is a suitable method to describe the strong spin-orbit coupling of Ce and Gd. The lattice parameters of Ce_0.5Gd_0.5PO₄ match well with experimental values (1.39% error). The structural analysis showed that the lower symmetry of the [GdO₉] polyhedron corresponds to its lower defect stability when Gd occupies the Ce sites. For studies of chemical durability, the leach rates of Gd are relatively higher than those of Ce in pH?=?3–11 leachates, showing that the [GdO₉] polyhedrons with lower symmetry are more easily to be destroyed under leachates. While both Ce_0.5Gd_0.5PO₄ ceramics prepared by HPS (1150?°C) and PLS (1450?°C) had high chemical durability in all leachates, the ceramics prepared by PLS had lower leach rates in pH?=?3 leachates. This shows that PLS is a better method to prepare Ce_0.5Gd_0.5PO₄ ceramics.     

Phase evolution,microstructure and chemical stability of Ca1-xZr1-xGd2xTi2O7 (0.0 ≤ x ≤ 1.0) system for immobilizing nuclear waste

In order to ascertain the structural relationship of zirconolite and pyrochlore for their potential application in HLW immobilization, the Gd-doped zirconolite-pyrochlore composite ceramics (Ca_1-xZr_1-xGd_2xTi₂O₇) were systematically synthesized with x?=?0.0–1.0 by traditional solid-phase reaction method. The phase evolution and microstructure of the as-prepared samples have been elucidated by XRD and Rietveld refinement, Raman spectroscopy, BSE-EDS and HRTEM analysis. The results showed that zirconolite-2M, zirconolite-4M, perovskite and pyrochlore, four phases were identified in Ca_1-xZr_1-xGd_2xTi₂O₇ system and could be coexisted at x?=?0.4 composition. With the increase of Gd³⁺ substitution, the phase evolution was followed by zirconolite-2M→zirconolite-4M→pyrochlore. It is illustrated that the phase transformation from zirconolite-2M to zirconolite-4M was promoted by the preferential substitution of Gd³⁺ for Ca²⁺. And the solubility of Gd³⁺ in zirconolite-2M, zirconolite-4M and pyrochlore increased in sequence. The chemical stability test was also measured by the PCT leaching method. The normalized elemental release rates of Ca, Zr, Ti and Gd in Ca_1-xZr_1-xGd_2xTi₂O₇ system were fairly low and in the range of 10^?6?10^?8 g?m^?2 d^?1, which indicated a potential ceramics composite ensemble of CaZrTi₂O₇-Gd₂Ti₂O₇ system for nuclear HLW immobilization.     

New Lead‐free (1−x)BaTiO3–xBi(Mg1/2Zr1/2)O3 Solid Solution with Morphotropic Phase Boundary and Diffuse Phase Transition

A new lead‐free perovskite solid solution (1?x)BaTiO₃–xBi(Mg_1/2Zr_1/2)O₃ with morphotropic phase boundary (MPB) has been developed, and its structural and dielectric properties have been investigated. Rietveld structural analysis of the X‐ray diffraction data suggest a composition‐dependent tetragonal (P4mm) to cubic () phase transition with an intermediate, phase coexistence region, demarcating the MPB. The compositions with x ≤ 0.05 are tetragonal in the P4mm space group and the compositions with x ≥ 0.25 are cubic in the space group. Coexistence of monoclinic phase (space group Cm) with tetragonal/cubic phase (space group P4mm/) is observed in the MPB region for the compositions with 0.10 ≤ x ≤ 0.22. The temperature dependence of permittivity exhibits a nonrelaxor type diffuse phase transition for all the compositions across the MPB.     

The effect of ZrO2 alloying on the microstructures and thermal properties of DyTaO4 for high-temperature application

High fracture toughness of 8 YSZ (8 wt% yttria-stabilized zirconia) is linked to its ferroelastic toughening mechanism. In this work, the similar ferroelastic domain is detected in monoclinic Dy_1−xTa_1−xZr_2xO₄ ceramics, which derives from the ferroelastic transformation between the high-temperature tetragonal (t) and low-temperature monoclinic (m) phase. The lowest thermal conductivity of Dy_1−xTa_1−xZr_2xO₄ ceramics is reduced by 30% compared with 8 YSZ, and the largest thermal expansion coefficients (TECs) is up to 11 × 10⁻⁶ K⁻¹ at 1200°C, which is comparable to that of 8 YSZ. Notably, the systematic investigations containing phase, microstructure, thermophysical properties of Dy_1−xTa_1−xZr_2xO₄ ceramics will provide guidance for its high-temperature application, especially as thermal barrier coatings.