Fabrication and phase transition of uranium-doped LaxGd2−xZr2O7 transparent ceramics: A prospective neutron detection material

Via vacuum sintering, 2 mol% uranium-doped La_xGd_2−xZr₂O₇ (x = 2, 1.6, 1, and 0.4) transparent ceramics with Ca²⁺ as charge compensator was first fabricated by solid-state reaction. X-ray diffraction results of as-prepared powders and ceramic samples demonstrate that the phase transition from defective fluorite to pyrochlore occurs with the increase of x. Optical in-line transmittance spectrum shows that four ceramic samples have good in-line transmittance (nearly 80% from 700 to 2200 nm), especially the U:La_1.6Gd_0.4Zr₂O₇ ceramics. The cut-off wavelength of four U-doped transparent ceramics shifted from 250 to near 460 nm, and it is believed that such phenomenon is related to the stable existence form of uranium in ceramics lattices. Observing the excitation emission spectra, the main excitation peaks of four ceramic samples are located at 458 nm, and the main emission peaks are located around 513 nm. In addition, there are low-intensity emission peaks around 520, 537, and 566 nm, and the related explanation is given in combination with the U⁶⁺ ion energy level diagram. Thus, uranium-doped La_xGd_2−xZr₂O₇ transparent ceramics have potential for novel neutron detection materials.     

Effect of CaO doping on densification and microstructure control of highly transparent La0.4Gd1.6Zr2O7 ceramics

Calcium oxide (CaO) as sintering additive was first used to fabricate La_0.4Gd_1.6Zr₂O₇ transparent ceramics by a simple solid-state reaction and one-step vacuum sintering method. The effects of CaO dopant amount on the densification, as well as sintering behaviors and microstructure evolution of the as-fabricated La_0.4Gd_1.6Zr₂O₇ ceramics, were systematically investigated. Under the different sintering temperatures, the relationships during the sintering process between grain growth and zpore elimination were analyzed as well. It was found that 0.1 wt% CaO doping can effectively control the rate of grain growth and promote densification dominated by surface diffusion. Furthermore, Ca²⁺ entered the lattice of La_0.4Gd_1.6Zr₂O₇ ceramics to accelerate ion diffusion and suppress grain boundary migration. With the introduction of 0.1 wt% CaO doping, the highly transparent La_0.4Gd_1.6Zr₂O₇ ceramics (T = 80.4% at 1100 nm) were successfully fabricated at the traditional sintering temperature (1850°C).     

Effect of Gd Content on Luminescence Properties of Eu3+‐Doped La2−xGdxZr2O7 Transparent Ceramics

3 at.% Eu³⁺‐doped La_2?xGd_xZr₂O₇ (x = 0–2.0) transparent ceramics were fabricated by vacuum sintering. The effect of Gd content on crystal structure, in‐line transmittance, and luminescence property of the ceramics were investigated. The ceramics are all cubic pyrochlore structure with high transparency. The cut‐off edge of the transmittance curve of the ceramics varied with Gd content and was also affected by the annealing process. The luminescence intensity became stronger for the ceramics annealed in air. As Gd content increased, the energy band structure as well as the luminescence behavior of the ceramics was changed; in addition, the symmetry of the crystal lattice reduced, resulting in the shift of the strongest luminescence peak from 585 nm to around 630 nm.     

Vacuum sintering of highly transparent La1+xYb1+yZr2O7 ceramics with excess La and Yb contents

In this study, a series of transparent ceramics with chemical composition of La_1+xYb_1+yZr₂O₇ (x, y = 0.1?0.5) were successfully prepared by vacuum sintering using combustion synthesized powders. The effects of excess contents on the phase composition, microstructure and in-line transmittance have been studied. The detailed results indicate that the in-line transmittance increases at first and then decreases as La content be elevated. It was also determined that the highest in-line transmittance of La_1+xYb_1+yZr₂O₇ (x, y = 0.1?0.5) ceramics is 84.1 % at 1100 nm when the excess amount of co-doped La-Yb is 30 %. Compared with stoichiometric LaYbZr₂O₇ ceramic, the nonstoichiometric La_1+xYb_1+yZr₂O₇ (x, y = 0.1?0.5) ceramics exhibit much higher transparency. In addition, the high excess amount of La, Yb and co-doped La-Yb also shows effects on the phase composition and crystal structure.     

Preparation of multicomponent A2Zr2O7 transparent ceramics by vacuum sintering

Recently, high-entropy oxide ceramics have become a hot topic in the field of high entropy materials. In this paper, multicomponent pyrochlore A₂Zr₂O₇ transparent ceramics were prepared via vacuum sintering using combustion synthesized nanopowders. The phase analysis results indicate that the powders exhibit defective fluorite structure and the ceramics are in pyrochlore structure. The structural order degree of ceramics varies with the increase of incorporated components. It is found that the grain size of A₂Zr₂O₇ ceramics is related with the component of A-site. The main fracture mode of final ceramics exhibit typical transgranular fracture. The multicomponent A₂Zr₂O₇ ceramics exhibit excellent optical transmittance, and the highest in-line transmittance reaches to 80% for #A2ZO ceramic at 1880 nm.     

Potential of pyrochlore structure materials in solid oxide fuel cell applications

Pyrochlore structure material (A₂B₂O₇) has gained interest in diverse applications like catalysis, nuclear waste encapsulation, sensors, and various electronic devices due to the unique crystal structure, electrical property, and thermal stability. This review deals with the ionic/electronic conductivity of numerous pyrochlore structure materials (titanates, zirconates, hafnates, stannates, niobates, ruthenates, and tantalite based pyrochlore) as electrolyte and electrode materials for solid oxide fuel cells (SOFCs). The impact of cation radius ratio (r_A/r_B) on the lattice constant and oxygen ‘x’ parameter of different pyrochlore structure materials obtained by various synthesis methods are reported. Higher ionic conductivity is essential for better ion transport in an electrolyte, and mixed ionic and electronic conductivity in electrode is essential for attaining higher efficiency in a typical SOFC. Gd_xTi₂O_7-δ, Gd_2-xCa_xTi₂O_7-δ, Nd_2-yGd_yZr₂O₇, Y₂Zr₂O₇, Y₂Zr_2-xMn_xO_7-δ, SmDy_1-xMg_xZr₂O_7-x/2, Gd_2-xCa_xTi₂O_7-δ pyrochlore are reported as electrolytes for fuel cell applications. Some pyrochlore material (La_2-xCa_xZr₂O₇, Sm_2-xM_xTi₂O₇ (M = Mg, Co, and Ni) pyrochlore) shows protonic conductivity at lower temperatures and ionic conductivity at higher temperature condition. Also, the mixed ionic-electronic conductivity behavior is reported in electrode materials for SOFC such as R₂MnTiO₇ (R = Er and Y), R₂MnRuO₇ (R = Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y), R₂Ru₂O₇ (R = Bi, Pb and Y), Y_2-xPr_xRu₂O₇, Ni-(Gd_0.9Ca_0.1)₂Ti₂O_7-δ, (Gd_0.9Ca_0.1)₂Ti₂O_7-δ, Gd₂(Ti_0.8Ru_0.2)₂O_7-δ, (Sm_0.9Ca_0.1)₂Ti₂O_7-δ and (Y_0.9Ca_0.1)₂Ti₂O_7-δ pyrochlore. The detailed study of the electronic behavior of these pyrochlore system confirms the necessity of defect structure with high oxygen mobility, lower activation energy, ionic radii ratio criterion should satisfy, and possess notable ion-ion interaction. Ionic conductivity in pyrochlore is increased by enhancing the oxygen migration through 48f-48f site with the formation of oxygen vacancy. Vacancy formation can be achieved by adding a suitable dopant that creates oxygen vacancy by charge compensation mechanism or as anion Frenkel defects. Similarly, the electrical conductivity is improved while adding suitable dopant (Ce, Pr, Ru, etc.) due to disordered structure and anti-Frenkel defect formation which leads to oxygen vacancy formation and thus improves conductivity.     

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.     

Influence of doping Mg2+ or Ti4+ captions on the microstructures,thermal radiation and thermal cycling behavior of plasma-sprayed Gd2Zr2O7 coatings

Gadolinium zirconate (Gd₂Zr₂O₇) coatings doped by the transition metal Ti and the alkaline earth metal Mg were expected to have improved thermal radiation performance, which could be combined with their excellent thermal barrier properties to comprehensively improve the thermal insulating performance. The results show that the parent Gd₂Zr₂O₇ powder as well as the Gd-site and Zr-site substituted powders crystallize as pyrochlore Gd₂Zr₂O₇ in Fd-3m space group, while all the as-sprayed coatings have the combination of fluorite and a little part of pyrochlore phase. Gd₂Zr₂O₇ ceramic has high mid-infrared emittance and the addition of Ti⁴⁺ into Gd₂Zr₂O₇ can enhance the infrared absorption/emittance in a specific wavenumber range, dominantly in the near-infrared (0.75–2.5 μm) band due to the enhancement of electron transition induced by the impurity energy levels linked to the widening of the conduction band. The normal spectral infrared emissivity of Gd₂Zr₂O₇-based coating was higher than 0.88 at 1073 K. The monolayered doped Gd₂Zr₂O₇ coatings present very low thermal cycling lifetime, similar with the parent coating, mainly related with their low fracture toughness, despite (Gd_1-xMg_x)₂Zr₂O₇ series display lower thermal conductivity than the parent one.     

Influence of magnesia doping on structure and electrical conductivity of pyrochlore type GdSmZr2O7

Abstract

Polycrystalline ceramic samples of magnesia doped GdSm_1–xMg_xZr₂O_7–x/2 have been prepared by conventional solid state reaction method using high purity oxides. The influence of magnesia dopant content on densification, microstructure and electrical properties of GdSm_1–xMg_xZr₂O_7–x/2 ceramics are investigated. Magnesia doping promotes the sintering densification behaviour of GdSm_1–xMg_xZr₂O_7–x/2 ceramics. GdSm_1–xMg_xZr₂O_7–x/2 (x?=?0, 0·05, 0·10) ceramics have a single phase of the pyrochlore type structure, while GdSm_1–xMg_xZr₂O_7–x/2 (x?=?0·15, 0·20) ceramics consist of the pyrochlore type structure and a small amount of magnesia as the second phase. The total conductivity of GdSm_1–xMg_xZr₂O_7–x/2 ceramics obeys the Arrhenius relation, and gradually increases with increasing temperature from 723 to 1173 K. GdSm_1–xMg_xZr₂O_7–x/2 ceramics are oxide-ion conductors in the oxygen partial pressure range of 1·0×10^–4 to 1·0 atm at each test temperature. The maximum value of the total conductivity is 1·29×10^–2 S cm^–1 at 1173 K for the GdSm_0·85Mg_0·15Zr₂O_6·925 ceramic.     

Rapid synthesis of Gd2Zr2O7 ceramics by flash sintering and its aqueous durability

The high radiation resistance and long time stability of Gd₂Zr₂O₇ ceramics make it a promising candidate for high level waste (HLW) immobilization materials. In this study, single phase nanocrystalline Gd₂Zr₂O₇ was successfully synthesized and consolidated at temperatures around 1050 °C for only 1 min by flash sintering for the first time. The phase evolution and microstructural development during flash sintering were systematically studied and compared with the conventionally sintered samples. The flash sintered Gd₂Zr₂O₇ exhibit defect fluorite structure, and a following heat treatment at 1400 °C could transform the Gd₂Zr₂O₇ ceramics from defect fluorite phase into pyrochlore phase. The MCC-1 leaching test shows that the flash sintered Gd₂Zr₂O₇ samples exhibit good aqueous durability.     

Marked reduction in the thermal conductivity of (La0.2Gd0.2Y0.2Yb0.2Er0.2)2Zr2O7 high-entropy ceramics by substituting Zr4+ with Ti4+

The (La_0.2Gd_0.2Y_0.2Yb_0.2Er_0.2)₂(Zr_1-xTi_x)₂O₇ (x = 0–0.5) high-entropy ceramics were successfully prepared by a solid state reaction method and their structures and thermo-physical properties were investigated. It was found that the high-entropy ceramics demonstrate pure pyrochlore phase with the composition of x = 0.1–0.5, while (La_0.2Gd_0.2Y_0.2Yb_0.2Er_0.2)₂Zr₂O₇ shows the defective fluorite structure. The sintered high-entropy ceramics are dense and the grain boundaries are clean. The grain size of high-entropy ceramics increases with the Ti⁴⁺ content. The average thermal expansion coefficients of the (La_0.2Gd_0.2Y_0.2Yb_0.2Er_0.2)₂(Zr_1-xTi_x)₂O₇ high-entropy ceramics range from 10.65 × 10^?6 K^?1 to 10.84 × 10^?6 K^?1. Importantly, the substitution of Zr⁴⁺ with Ti⁴⁺ resulted in a remarkable decrease in thermal conductivity of (La_0.2Gd_0.2Y_0.2Yb_0.2Er_0.2)₂(Zr_1-xTi_x)₂O₇ high-entropy ceramics. It reduced from 1.66 W m^?1 K^?1 to 1.20 W m^?1 K^?1, which should be ascribed to the synergistic effects of mass disorder, size disorder, mixed configuration entropy value and rattlers.     

Study on La2(Hf1-xTix)2O7 (x ≤ 0.20) pyrochlores for potential thermal/environmental barrier coating applications

Lanthanum hafnate (La₂Hf₂O₇) with a pyrochlore structure has excellent high temperature stability and low thermal conductivity, which is promising for thermal/environmental barrier coatings (T/EBCs) applications. To reduce its thermal expansion coefficient (TEC) so as to better match SiC_f/SiC composites, a smaller tetravalent dopant Ti⁴⁺ has been introduced in the Hf-sites to form La₂(Hf_1-xTi_x)₂O₇ (x ≤ 0.20). The phase composition and microstructure confirms that La₂(Hf_1-xTi_x)₂O₇ solid solutions possess a pure pyrochlore structure. With an increase of x, their TECs are decreasing consistently, whilst their thermal conductivities of La₂(Hf_1-xTi_x)₂O₇ are slightly increasing at high temperature but still much lower than those of meta-stable yttria partially stabilized zirconia, both of which are attributing to an increase of elastic modulus after Ti⁴⁺ doping on Hf-sites. The extremely excellent high temperature stability, relatively low thermal conductivities and low TECs suggest that La₂(Hf_1-xTi_x)₂O₇ is a prospective candidate material for T/EBC applications.     

Characterizations of vacuum sintered Gd2Zr2O7 transparent ceramics using combustion synthesized nanopowder

Highly transparent Gd₂Zr₂O₇ ceramic was fabricated by vacuum sintering using combustion synthesized nanopowder with mean particle size of about 80 nm. The morphology and structure were analyzed by X-ray diffractometer, scanning electron microscopy, Raman spectroscopy and transmission electronic microscopy. The Gd₂Zr₂O₇ nanopowder and transparent ceramic are both in low ordered pyrochlore structure. The effects of sintering temperature on the density and transmittance of Gd₂Zr₂O₇ ceramic were investigated, and the optimum sintering temperature (1825 °C) was obtained. Gd₂Zr₂O₇ transparent ceramic sintered at 1825 °C for 6 h shows the highest transmittance of 77.3 % and the average grain size of about 80 μm.     

High-entropy transparent (Y0.2La0.2Gd0.2Yb0.2Dy0.2)2Zr2O7 ceramics as novel phosphor materials with multi-wavelength excitation and emission properties

High-entropy ceramics have been extensively studied because of their novel intrinsic properties and have significant potential for application in various fields. In this study, a novel high-entropy transparent ceramic phosphor (Y_0.2La_0.2Gd_0.2Yb_0.2Dy_0.2)₂Zr₂O₇ was successfully prepared via a solid-state reaction and vacuum sintering. X-ray diffraction and scanning electron microscopy analyses were performed to analyze the phases and microstructures of the as-prepared powders and sintered ceramics. The highest in-line transmittance of the developed ceramic was 74 % in both visible and infrared regions. To reveal its luminescent properties as a potential WLED material, the photoluminescence of ceramic samples was analyzed using multi-excitation and emission spectra. Strong emissions originating from Dy³⁺ and Gd³⁺ were observed, and the emission color was effectively regulated under multi-wavelength excitation. Combining excellent optical transmittance with unique photoluminescence performance, the (Y_0.2La_0.2Gd_0.2Yb_0.2Dy_0.2)₂Zr₂O₇ high-entropy transparent ceramics can find potential applications as a novel WLED material with multi-wavelength excitation and tunable emission.     

Coprecipitation synthesis and sintering property of (YbxSm1-x)2Zr2O7 ceramic powders

Abstract

Abstract

(Yb_xSm_1-x)₂Zr₂O₇ (0<x<1·0) ceramic powders were synthesised with chemical coprecipitation and calcination method. Thermal decomposition behaviour of precipitates was studied by differential scanning calorimetry-thermogravimetry. The powders were characterised by X-ray diffractometry, scanning electron microscopy and transmission electron microscopy with energy dispersive spectroscopy. The synthesised powders have a particle size of about 100?nm, and exhibit to a certain extent agglomeration. The sintering behaviour of (Yb_xSm_1-x)₂Zr₂O₇ powders was studied by pressureless sintering method at 1550-1700°C for 10?h in air. The relative densities of (Yb_xSm_1-x)₂Zr₂O₇ ceramics increase with increasing sintering temperature, and reach above 95% when sintered at 1700°C for 10?h in air. Sm₂Zr₂O₇ and (Yb_0·1Sm_0·9)₂Zr₂O₇ ceramics have a pyrochlore structure; however, (Yb_xSm_1-x)₂Zr₂O₇ (0·3<x<1·0) ceramics exhibit a defective fluorite type structure.     

A novel NTC ceramic based on La2Zr2O7 for high-temperature thermistor

A novel negative temperature coefficient material based on lanthanum zirconate ceramics was proposed for high-temperature applications. This material was synthesized through a solid-state reaction by sintering at 1923 K for 10 h in air. The X-ray diffraction and scanning electron microscopy results confirmed that La₂Zr₂O₇ ceramics exhibited a pyrochlore phase with a relative density of 98.2 %. The resistance–temperature characteristics of the material revealed that La₂Zr₂O₇ ceramics exhibited an NTC feature within the broad temperature range of 973–1773 K in addition to maintaining high thermal constant B, and resistivity to ensure good sensitivity at high temperatures. These properties, along with high ceiling temperature, unique oxygen insensitivity, and excellent ageing coefficient of <0.7 % at 1773 K, render La₂Zr₂O₇ ceramics a promising candidate as thermistor materials with high-temperature NTC.     

Effects of Yb3+ doping on phase structure,thermal conductivity and fracture toughness of (Nd1-xYbx)2Zr2O7

To investigate the effects of Yb³⁺ doping on phase structure, thermal conductivity and fracture toughness of bulk Nd₂Zr₂O₇, a series of (Nd_1-xYb_x)₂Zr₂O₇ (x?=?0, 0.2, 0.4, 0.6, 0.8, 1.0) ceramics were synthesized using a solid-state reaction sintering method at 1600?°C for 10?h. The phase structures were sensitive to the Yb³⁺ content. With increasing doping concentration, a pyrochlore-fluorite transformation of (Nd_1-xYb_x)₂Zr₂O₇ ceramics occurred. Meanwhile, the ordering degree of crystal structure decreased. The substitution mechanism of Yb³⁺ doping was confirmed by analyzing the lattice parameter variation and chemical bond of bulk ceramics. The thermal conductivities of (Nd_1-xYb_x)₂Zr₂O₇ ceramics decreased first and then increased with the increase of Yb³⁺ content. The lowest thermal conductivity of approximately 1.2?W?m^?1 K^?1 at 800?°C was attained at x?=?0.4, around 20% lower than that of pure Nd₂Zr₂O₇. Besides, the fracture toughness reached a maximum value of ~1.59?MPa?m^1/2 at x?=?0.8 but decreased with further increasing Yb³⁺ doping concentration. The mechanism for the change of fracture toughness was discussed to result from the lattice distortion and structure disorder caused by Yb³⁺ doping.     

Preparation of Gd2Zr2O7 nanopowders by polyacrylamide gel method and their sintering behaviors

Well-crystallized and good-dispersed Gd₂Zr₂O₇ nanopowders with defect-fluorite structure are successfully prepared by the polyacrylamide gel method. The mole ratio of acrylamide/Gd and calcination temperature have the significant effects on the phase composition, particle size, and agglomeration degree of the Gd₂Zr₂O₇ nanopowders. The sintering behaviors of the as-prepared Gd₂Zr₂O₇ nanopowders are investigated at temperatures of 1200?1500 °C. The Gd₂Zr₂O₇ nanopowders can be sintered into dense ceramics with a high relative density of 98 % at 1500 °C for 2 h. Moreover, the defect-fluorite phase of Gd₂Zr₂O₇ transforms to pyrochlore phase of Gd₂Zr₂O₇ with the increase of sintering temperature. In addition, the two-step sintering is performed to prepare the Gd₂Zr₂O₇ nanoceramics using the as-prepared Gd₂Zr₂O₇ nanopowders as starting materials. This work presents a simple and industrially feasible approach for preparing the Gd₂Zr₂O₇ nanopowders with excellent sinterability.     

Thermophysical performances of (Gd1-xYbx)2AlTaO7 oxides for high-temperature heat-insulation coating applications

Newly developed (Gd_1-xYb_x)₂AlTaO₇ oxides for high-temperature heat-insulation coatings were prepared using a multi-step solid-state fritting method. The important features of synthesized oxides including phase composition, thermal conductivity and expansion performances were studied. It is investigated that the fabricated ceramics are confirmed to possess a sole pyrochlore crystal structure. Owing to the influence of the strain fields and mass fluctuations caused by Yb₂O₃ addition, thermal conductivities of (Gd_1-xYb_x)₂AlTaO₇ oxides are lower than that of Gd₂AlTaO₇ or Yb₂AlTaO₇, and the (Gd_0.9Yb_0.1)₂AlTaO₇ exhibits the lowest thermal expansion coefficient. Due to the synergic effects of the relatively high electro-negativity of Yb³⁺, decedent lattice order, and numerous oxygen vacancies, the thermal expansion coefficients increase gradually with increasing Yb₂O₃ content. The thermophysical performances of (Gd_1-xYb_x)₂AlTaO₇ oxides satisfy the conditions for high-temperature heat-insulation coatings.     

Glycol-citrate synthesis of fine-grained oxides La2−xGdxZr2O7 and preparation of corresponding ceramics using FAST/SPS process

Single-phase superfine refractory oxides of composition La_2?xGd_xZr₂O₇ (x = 0, 0.5, 1, 1.5, 2) have been synthesized using glycol-citrate route. Dependencies of degree of dispersion and phase composition on chemical composition for such oxides were determined. Fluorite-pyrochlore transition observed during thermal treatment of these oxides was examined. It was stated that this transition occurred in the temperature range 1000–1200?°C for all formulations with exception of gadolinium zirconate Gd₂Zr₂O₇ which kept the fluorite structure even after long-term exposure (4?h) at a temperature of 1400?°С. Samples of corresponding ceramics which density amount to 95–98% of the theoretical value were obtained using FAST/SPS process. Coefficients of linear thermal expansion (CLTE) of manufactured materials were measured. It was found that CLTE values for all samples except for gadolinium zirconate were independent of temperature in the range 400–1000?°C. It was shown that Gd₂Zr₂O₇ kept the fluorite structure under conditions of FAST/SPS process at a temperature of 1600?°C.