共查询到20条相似文献,搜索用时 31 毫秒
1.
《Ceramics International》2019,45(13):16450-16457
The study underlines the impact of Ti4+ substitution in Gd2Zr2O7 for applications in thermal barrier coatings (TBC). Depending on the Ti4+ content, two different crystal structures of Gd2Zr2O7 namely pyrochlore and fluorite were determined. Ti4+ substitutions in the increasing order induced a gradual contraction of Gd2Zr2O7 unit cell; however, with the accomplishment of concentration dependent crystal structures of either single phase pyrochlore or mixtures of pyrochlore and fluorite. Absorption measurements enunciated the enhanced infra-red reflectance behaviour of Gd2Zr2O7 due to Ti4+ substitutions. A gradual increment in the concentration of Ti4+ substitutions in Gd2Zr2O7 envisaged a simultaneous porous to dense morphological features, which reflected in the resultant mechanical data. Hot corrosion studies ensure the critical role of Ti4+ to retain the crystal structure of Gd2Zr2O7. 相似文献
2.
《Ceramics International》2020,46(2):1352-1361
Molten-salt method has been used to synthesize various functional materials, but it has not been employed to adjust the structure, particle size, and properties of preformed particles. To fill the knowledge gap, in this study, we use a molten-salt medium to reprocess preformed La2Zr2O7:5%Eu3+ nanoparticles which were already formed by a molten-salt synthesis (MSS) method. The molten-salt processing is conducted under various conditions in terms of processing time, temperature, and medium. Specifically, within the studied molten-salt processing time (0 h–24 h) at 800°C, 3 h was found to offer the best optical output. In terms of the investigated molten-salt processing temperature (650 °C–1100 °C) for 3 h, 800 °C was identified as the most desirable annealing temperature. Regarding the explored molten-salt processing media (nitrate vs. chloride) at 3 h and 800 °C, better luminescence results were obtained for nanoparticles processed in chloride. Under each processing parameter, the change of optical properties is explained based on the balance among the crystalline size, crystal structure, crystallinity, defect, and agglomeration characteristics of the molten salt processed La2Zr2O7:5%Eu3+ particles. We expect this study will excite other scientists to further explore molten-salt processing as an effective post-synthesis method to fine-tune the structure, particle size, and properties of preformed particles to meet the demand of functional materials. 相似文献
3.
《Journal of the European Ceramic Society》2022,42(13):6085-6096
A series of ceramic samples were prepared to experimentally investigate sub-solidus phase relations in the La2O3-Sm2O3-ZrO2 system at 1873 K and 1673 K. No ternary compounds have been observed, while the binary La2Zr2O7 and Sm2Zr2O7 pyrochlore phases form a continuous solid solution La2?xSmxZr2O7 in the ternary system at the selected temperatures. X-ray diffraction and microstructure results demonstrated that the pyrochlore phase is stable in the ZrO2-rich corner. The homogeneity range of the pyrochlore phase was carefully determined and the phase boundary of the cubic ZrO2 (fluorite phase) which extends into the ternary system was also constructed via electron probe microanalysis. The as-obtained data were adopted to determine the mixing parameters for the pyrochlore and fluorite phases in the present thermodynamic modeling. A self-consistent database of the La2O3-Sm2O3-ZrO2 system was accordingly established for the first time and the calculations agree well with the experimental data in the current work. 相似文献
4.
Yiming Li Xuanyu Meng Qian Chen Jiatong Zhu Jie Xu Michael J. Reece Feng Gao 《Journal of the American Ceramic Society》2021,104(3):1475-1488
By applying the first-principles calculation, the electronic structure, mechanical and thermal properties of Sm3+-doped La2Zr2O7 were investigated, and experiments were carried out to verify the theoretical results. As the Sm3+ doping rate increases, the lattice parameters decrease while the theoretical density increases. The doping of Sm3+ promotes the transformation from pyrochlore structure to defective fluorite structure. The Young's modulus of pure La2Zr2O7 shows obvious anisotropy, while it tends to be isotropy with the doping of Sm3+. The calculated theoretical hardness is positively correlated with the doping rate, yet due to the solid solution strengthening effect, the materials with doping rate of 50% get the highest hardness. Based on the calculations and experiments, the optimal Sm3+ doping rate of La2Zr2O7 is 50%. LaSmZr2O7 has hardness of 11.35 GPa, the thermal conductivity of 1.35 W/(m·K) at 1173 K, and the thermal expansion coefficient of 10.12 × 10−6/K at 1173 K. The above results indicate that LaSmZr2O7 has good mechanical and thermal properties, which provides new ideas for the selection of thermal barrier coating materials. 相似文献
5.
《Ceramics International》2022,48(12):17157-17170
Pure pyrochlore Ca2Ti2O6, perovskite CaTiO3, and their mixed crystalline phases with different proportions were controllably synthesized via a solvothermal method, followed by a subsequent calcination process. RIR (reference intensity ratio) data of Ca2Ti2O6 were first obtained by X-ray diffraction (XRD), which can be used to quantitatively analyze the phase composition. When Eu3+ is doped into these calcium titanium oxides, they can be used as luminescent and photocatalytic materials. The structure, luminescence, and photocatalytic properties of pure pyrochlore Ca2Ti2O6:Eu3+ and perovskite CaTiO3:Eu3+ were comparatively studied in detail. The relative intensities of the excitation peaks and the emission peaks in Ca2Ti2O6:Eu3+ and CaTiO3:Eu3+ are different, which is attributed to the different symmetries of Eu3+ inhabiting the two kinds of lattices. In addition, although the luminescence intensity of CaTiO3:3%Eu3+ is higher than that of Ca2Ti2O6:3%Eu3+ under excitation at 394 nm, the luminescence intensity of Ca2Ti2O6:3%Eu3+ is superior to that of CaTiO3:3%Eu3+ under excitation at 464 nm and 533 nm. Photocatalytic experiments show that Ca2Ti2O6:3%Eu3+ has better photocatalytic performance than CaTiO3:3%Eu3+, which is mainly due to its smaller crystallite size, higher specific surface area and pyrochlore structure. In addition, biphase (Ca2Ti2O6–CaTiO3):3%Eu3+ has the best photocatalytic activity compared with the single phase Ca2Ti2O6:3%Eu3+ and CaTiO3:3%Eu3+, owing to the presence of heterojunctions that significantly reduced the band gap. It is anticipated that the discovery of this bifunctional Ca2Ti2O6:Eu3+ would expand the application of rare earth-doped calcium titanium oxide materials. 相似文献
6.
《应用陶瓷进展》2013,112(1):54-57
AbstractAbstractMaterials with A2B2O7 (pyrochlore) structure have received significant attention for their applications as new protonic conductors and materials used in electronic devices. One of the unique synthesis routes for La2Zr2O7 (pyrochlore) powders is the glycine–nitrate combustion method, which shows superior properties of the synthesised powder using glycine as a complexing agent. The Sr doped La2Zr2O7 powders in pure pyrochlore structure were produced using this approach. Selected characteristics of the synthesised powders, such as crystal structure, lattice parameters, crystallite size, the vibrational properties, the morphology of the particles, along with the specific surface area and particle size, have been investigated. The dependence of some properties on annealing temperatures of the powders has been studied. 相似文献
7.
Santosh K. Gupta Maya Abdou Partha S. Ghosh Jose P. Zuniga Ezhilarasan Manoharan HyeongJun Kim Yuanbing Mao 《Journal of the American Ceramic Society》2020,103(1):235-248
Unveiling the underlying mechanisms of properties of functional materials, including the luminescence differences among similar pyrochlores A2B2O7, opens new gateways to select proper hosts for various optoelectronic applications by scientists and engineers. For example, although La2Zr2O7 (LZO) and La2Hf2O7 (LHO) pyrochlores have similar chemical compositional and crystallographic structural features, they demonstrate different luminescence properties both before and after doped with Eu3+ ions. Based on our earlier work, LHO-based nanophosphors display higher photo- and radioluminescence intensity, higher quantum efficiency, and longer excited state lifetime compared to LZO-based nanophosphors. Moreover, under electronic O2−→Zr4+/Hf4+ transition excitation at 306 nm, undoped LHO nanoparticles (NPs) have only violet blue emission, whereas LZO NPs show violet blue and red emissions. In this study, we have combined experimental and density functional theory (DFT) based theoretical calculation to explain the observed results. First, we calculated the density of state (DOS) based on DFT and studied the energetics of ionized oxygen vacancies in the band gaps of LZO and LHO theoretically, which explain their underlying luminescence difference. For Eu3+-doped NPs, we performed emission intensity and lifetime calculations and found that the LHOE NPs have higher host to dopant energy transfer efficiency than the LZOE NPs (59.3% vs 24.6%), which accounts for the optical performance superiority of the former over the latter. Moreover, by corroborating our experimental data with the DFT calculations, we suggest that the Eu3+ doping states in LHO present at exact energy position (both in majority and minority spin components) where oxygen defect states are located unlike those in LZO. Lastly, both the NPs show negligible photobleaching highlighting their potential for bioimaging applications. This current report provides a deeper understanding of the advantages of LHO over LZO as an advanced host for phosphors, scintillators, and fluoroimmunoassays. 相似文献
8.
Jianying Xiang Shuhai Chen Jihua Huang Hua Zhang Xingke Zhao 《Ceramics International》2012,38(5):3607-3612
La2Zr2O7 has high melting point, low thermal conductivity and relatively high thermal expansion which make it suitable for application as high-temperature thermal barrier coatings. Ceramics including La2Zr2O7, (La0.7Yb0.3)2(Zr0.7Ce0.3)2O7 and (La0.2Yb0.8)2(Zr0.7Ce0.3)2O7 were synthesized by solid state reaction. The effects of co-doping on the phase structure and thermophysical properties of La2Zr2O7 were investigated. The phase structures of these ceramics were identified by X-ray diffraction, showing that the La2Zr2O7 ceramic has a pyrochlore structure while the co-doped ceramics (La0.7Yb0.3)2(Zr0.7Ce0.3)2O7 and the (La0.2Yb0.8)2(Zr0.7Ce0.3)2O7 exhibit a defect fluorite structure, which is mainly determined by ionic radius ratio r(Aav.3+)/r(Bav.4+). The measurements for thermal expansion coefficient and thermal conductivity of these ceramics from ambient temperature to 1200 °C show that the co-doped ceramics (La0.7Yb0.3)2(Zr0.7Ce0.3)2O7 and (La0.2Yb0.8)2(Zr0.7Ce0.3)2O7 have a larger thermal expansion coefficient and a lower thermal conductivity than La2Zr2O7, and the (La0.2Yb0.8)2(Zr0.7Ce0.3)2O7 shows the more excellent thermophysical properties than (La0.7Yb0.3)2(Zr0.7Ce0.3)2O7 due to the increase of Yb2O3 content. 相似文献
9.
《Ceramics International》2020,46(4):4737-4747
La2Zr2O7 used as a top coat material has low thermal conductivity and high stability at high temperature, but it also has a low fracture toughness, which limits its application. To improve the fracture toughness of La2Zr2O7, a La2Zr2O7@YSZ core–shell structured composite ceramic was designed and prepared. The morphology of the La2Zr2O7@YSZ composite ceramic was investigated using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The resulting images show that the YSZ is coated on the surface of the La2Zr2O7. The phases were analyzed by X-ray diffraction (XRD), and the XRD patterns show that pyrochlore and fluorite structures coexist in the La2Zr2O7@YSZ composite material without any chemical reaction. Differential scanning calorimetry (DSC) was used to detect the heat change of the composite ceramic during heat treatment. The properties of the La2Zr2O7@YSZ composite ceramic, such as the thermal conductivity, coefficient of thermal expansion (CTE), and mechanical properties were investigated using a laser flash method, high-temperature dilatometer, and nano-hardness tests, respectively. The thermal conductivity of the composite ceramic is in the range of 1.7745–2.3076 W m−1 K−1 in the temperature regime of 200–1000 °C. The maximum CTE of the composite ceramic is 10.3 × 10−6/°C. Owing to the thin YSZ coating on the La2Zr2O7 surface, the hardness and Young's modulus of the composite ceramic are 8.17 GPa and 168.3 GPa, respectively. The nucleation and propagation of micro-cracks are investigated using a micro-hardness tester. Compared to La2Zr2O7, the micro-cracks in the composite ceramic are shorter and more tortuous. The weak interface between the YSZ and La2Zr2O7 results in the nucleation and tortuous propagation of micro-cracks, which depletes part of the energy and improves the fracture toughness of the composite ceramic. The results reveal that the La2Zr2O7@YSZ composite ceramic has good mechanical and thermophysical properties. 相似文献
10.
《Ceramics International》2020,46(9):13054-13065
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 (Gd1-xMgx)2Zr2O7 series display lower thermal conductivity than the parent one. 相似文献
11.
《Journal of the European Ceramic Society》2022,42(14):6624-6632
Material with superior damage tolerance, chemical durability, and structure stability is of increasing interest in high-level radioactive waste management and structural components for advanced nuclear systems. In this paper, high-entropy (La0.2Ce0.2Nd0.2Sm0.2Gd0.2)2Zr2O7 with pyrochlore-type structure was synthesized through conventional solid-state method. The as-synthesized high-entropy oxide maintained crystalline after being irradiated by using Au3+ with 9.0 MeV energy at the fluence of 4.5 × 1015 ions·cm-2, indicating its high tolerance to heavy-ion irradiation. The irradiation-induced order-disorder transition from pyrochlore structure to defective fluorite structure occurred in high-entropy (La0.2Ce0.2Nd0.2Sm0.2Gd0.2)2Zr2O7. After irradiation, no irradiation-induced segregation was observed at grain boundary. Moreover, the mechanical properties of high-entropy pyrochlore were improved. The heavy-ion irradiation resistance mechanisms of high-entropy pyrochlore were discussed in detail. Our work identified high-entropy (La0.2Ce0.2Nd0.2Sm0.2Gd0.2)2Zr2O7 can be a promising candidate for immobilization of high-level radioactive waste as well as advanced nuclear reactor system from the perspective of irradiation resistance. 相似文献
12.
De-bao Liu Fei-fei Zhou Li-jie Qu Yi-guang Wang Bao-sheng Xu Shi-gang Ai 《Journal of the American Ceramic Society》2022,105(4):2772-2782
Porous La2Zr2O7 ceramic aerogels (CAs) were prepared by sol-gel template method and thermal treated process. The microstructure and crystallisation behavior of the samples were systematically characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and Raman spectroscopy. The results indicated that the as-prepared porous La2Zr2O7 CAs had a single-phase pyrochlore structure with typical three-dimensional (3-D) porous structure. Meanwhile, the formation mechanisms of the as-prepared porous La2Zr2O7 CAs were investigated. At the same time, the as-prepared porous La2Zr2O7 CAs presented an ultralow room-temperature thermal conductivity of 0.07 W/(m K), high specific surface areas of 325.17 m2/g, and a relatively high compressive strength of 11.95 MPa. What's more, the as-prepared porous La2Zr2O7 CAs possessed ideal photocatalytic activities due to its high crystallinity, large surface area as well as unique 3-D porous structure. Therefore, the present work is proposing some new insight to prepare rare-earth zirconates CAs with porous structures for thermal insulation and dye degradation applications. 相似文献
13.
Jiatong Zhu Xuanyu Meng Ping Zhang Zhuolun Li Jie Xu Michael J. Reece Feng Gao 《Journal of the European Ceramic Society》2021,41(4):2861-2869
A series of rare earth zirconates (RE2Zr2O7) high-entropy ceramics with single- and dual-phase structure were prepared. Compared with La2Zr2O7 and Yb2Zr2O7, the smaller “rattling” ions (Yb3+, Er3+, Y3+) have been incorporated into pyrochlore lattice in (La0.2Nd0.2Y0.2Er0.2Yb0.2)2Zr2O7 (LNYEY) while larger ions (La3+, Nd3+, Sm3+, Eu3+) incorporated into fluorite lattice in (La0.2Nd0.2Sm0.2Gd0.2Yb0.2)2Zr2O7 (LNSGY). Due to high-entropy lattice distortion and resonant scattering derived from smaller ions Yb3+, Er3+, and Y3+, LNYEY shows a lower glass-like thermal conductivity (1.62-1.59 W m-1 K-1, 100-600℃) than LNSGY (1.74-1.75 W m-1 K-1, 100-600℃). Moreover, LNYEY and LNSGY exhibit enhanced Vickers’ hardness (LNYEY, Hv = 11.47 ± 0.41 GPa; LNSGY, Hv = 10.96 ± 0.26 GPa) and thermal expansion coefficients (LNYEY, 10.45 × 10-6 K-1, 1000℃; LNSGY, 11.02 × 10-6 K-1, 1000℃). These results indicate that dual-phase rare-earth-zirconate high-entropy ceramics could be desirable for thermal barrier coatings. 相似文献
14.
《Ceramics International》2017,43(8):5941-5948
Core-shell and yolk–shell architectures are attracting great attention owing to their unique structure and infusive applications in the nanotechnology field. In this research, core-shell structured C@La2Zr2O7 nanospheres were synthesized through a facile technique using carbon spheres as templates. Lanthanum nitrate (La(NO3)3·6H2O) and zirconium oxychloride (ZrOCl2·8H2O) co-precipitated homogeneously on the surface of modified carbon spheres by adding ammonia dropwise. The close-to perfect spherical La2Zr2O7 hollow spheres were obtained by a two-step calcination of the C@La2Zr2O7 core-shell components, which were calcined at a high temperature in argon atmosphere and followed by low temperature oxidization calcination. SEM, TEM, XRD, and FTIR were used to characterize the morphology, size, composition, and crystal structure of synthesized products. The results show that La2Zr2O7 nanoparticles were attached tightly on the surface of carbon spheres through the functional groups, such as -OH, and O˭C-O-. After modified by NaOH, the carbon spheres surface possessed more abundant oxygen containing groups, resulting in much more La3+ and Zr4+ co-precipitated uniformly on their surface. Ultimately, an average diameter of the La2Zr2O7 hollow spheres was about 220 nm and the shell thickness was about 40 nm. Through controlling the oxidation calcination time, the morphology of the powders exhibited core-shell structured, yolk-shell structured and hollow structured spheres. Further, the formation mechanism of the hollow La2Zr2O7 spheres was elucidated. 相似文献
15.
《Ceramics International》2023,49(7):10936-10945
Pyrochlore-type La2Zr2O7 (LZ) is a promising candidate for high-temperature thermal barrier coatings (TBCs). However, its thermal expansion coefficient and low fracture toughness are not optimal for such application and thus, need to be improved. In this study, we systematically report the effect of CeO2 addition on phase formation, oxygen-ion diffusion, and thermophysical and mechanical properties of full compositions La2(Zr1?xCex)2O7 (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1). La2(Zr1?xCex)2O7 exhibits a pyrochlore structure at x ≤ 0.3, while a fluorite structure is observed outside this range. With the increase in CeO2 content, thermal expansion coefficient and oxygen-ion diffusivity in La2(Zr1?xCex)2O7 are increased. Oxygen-ion diffusivity of La2(Zr1?xCex)2O7 is two orders of magnitude less than that of classical 8YSZ. Among La2(Zr1?xCex)2O7 compounds, La2(Zr0.7Ce0.3)2O7 and La2(Zr0.5Ce0.5)2O7 exhibit relatively low oxygen diffusivities. The composition La2(Zr0.5Ce0.5)2O7 presents the lowest thermal conductivity due to the strongest phonon scattering and also the highest fracture toughness due to the solid-solution toughening. The highest sintering resistance is achieved by the composition La2(Zr0.7Ce0.3)2O7 because of its ordered pyrochlore structure and high atomic mass of Ce. Based on these results, the compositions La2(Zr0.5Ce0.5)2O7 and La2(Zr0.7Ce0.3)2O7 are alternatives for classical 8YSZ for TBC materials operating at ultrahigh temperatures. 相似文献
16.
O.A. Kornienko O.R. Andrievskaya O.I. Bykov A.V. Samelyuk Yu. M. Bataiev 《Journal of the European Ceramic Society》2021,41(6):3603-3613
According to the results of the samples studied by X-ray diffraction and microstructural analyzes the phase equilibria in the binary La2O3 – Sm2O3 and ternary ZrO2 – La2O3 – Sm2O3 systems were studied. The boundaries of the phase fields of the binary system are specified and an isothermal cross section of the ternary state diagram of the ZrO2 – La2O3 – Sm2O3 system at a temperature of 1500 °C is constructed. No new phases have been identified in the studied systems. It is established that in the ternary system ZrO2 – La2O3 – Sm2O3 at 1500 °C fields of solid solutions on the basis of cubic (F) modification with structure of fluorite type, tetragonal (T) modification of ZrO2, monoclinic (B) modifications of Sm2O3, hexagonal (A) are formed. La2O3, as well as an ordered phase with a structure of the type of pyrochlore Ln2Zr2O7 (Py). The boundaries of the phase fields and the parameters of the unit cells of the formed phases are determined. A characteristic feature of this isothermal cross section is the formation of a continuous series of solid solutions based on the phase of the pyrochlore type La2Zr2O7 (Sm2Zr2O7). The limiting solubility of Sm2O3 in the ordered phase La2Zr2O7 is 16 mol. % along the section Sm2O3- (67 mol.% ZrO2 - 33 mol.% La2O3). The solubility of La2O3 in the solid solution Sm2Zr2O7 is slightly less and is 11 mol. % along the section La2O3- (67 mol.% ZrO2 - 33 mol.% Sm2O3). The isothermal cross-section of the state diagram of the ZrO2 – La2O3 – Sm2O3 system at 1500 °C is characterized by the presence of three three-phase (Py + T + F), (A + Py + B), (Py + F + B) and eight two-phase (A + Py), (B + A), (B + Py), (F + B), (T + F), (Py + T), (F + Py-two) areas. 相似文献
17.
《Journal of the European Ceramic Society》2006,26(3):247-251
A series of La2O3–ZrO2–CeO2 composite oxides were synthesized by solid-state reaction. The final product keeps fluorite structure when the molar ratio Ce/Zr ≥ 0.7/0.3, and below this ratio only mixtures of La2Zr2O7 (pyrochlore) and La2O3–CeO2 (fluorite) exist. Averagely speaking, the increase of CeO2 content gives rise to the increase of thermal expansion coefficient and the reduction of thermal conductivity, but La2(Zr0.7Ce0.3)2O7 has the lowest sintering ability and the lowest thermal conductivity which could be explained by the theory of phonon scattering. Based on the large thermal expansion coefficient of La2Ce3.25O9.5, the low thermal conductivities and low sintering abilities of La2Zr2O7 and La2(Zr0.7Ce0.3)2O7, double-ceramic-layer thermal barrier coatings were prepared. The thermal cycling tests indicate that such a design can largely improve the thermal cycling lives of the coatings. Since no single material that has been studied so far satisfies all the requirements for high temperature thermal barrier coatings, double-ceramic-layer coating may be an important development direction of thermal barrier coatings. 相似文献
18.
《Ceramics International》2019,45(16):20078-20083
Transparent polycrystalline La2-xGdxZr2O7 (x = 0.4–2.0) ceramics were fabricated by solid-state reactive sintering using commercially available La2O3, Gd2O3 and ZrO2 nanopowders as the raw materials. The phase composition, microstructure evolution, densification and optical transmittance of the resulting ceramics were investigated. XRD and Raman results reveal that both the powders and ceramics are in single-phase pyrochlore structure. With the promotion of Gd content, the disorder degree of pyrochlore structure increases gradually while the cell parameters decrease. The x = 1.0, 1.2 and 1.6 samples exhibit high optical transmittance in the 450 nm-6.0 μm range, and the La0.4Gd1.6Zr2O7 sample shows the highest transmittance of 83.84%. The transparent La2-xGdxZr2O7 ceramics with high optical quality are available as scintillator matrice and high temperature window material. 相似文献
19.
《Ceramics International》2022,48(7):9602-9609
The (La0.2Gd0.2Y0.2Yb0.2Er0.2)2(Zr1-xTix)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 (La0.2Gd0.2Y0.2Yb0.2Er0.2)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 (La0.2Gd0.2Y0.2Yb0.2Er0.2)2(Zr1-xTix)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 (La0.2Gd0.2Y0.2Yb0.2Er0.2)2(Zr1-xTix)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. 相似文献
20.
《Ceramics International》2022,48(22):32946-32954
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. 相似文献