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Achieving full densification of some ceramic materials, such as Y2O3, without sintering aids by spark plasma sintering (SPS) is a great challenge when plastic deformation contributes limitedly to the densification as the yield stress of the material at an elevated temperature is higher than the applied sintering pressure. Herein, we demonstrate that particle fracture and rearrangement is an effective strategy to promote the densification during the pressure-assisted sintering process. Specifically, Y2O3 nanocrystalline powders composed of nanorod and near-spherical particles were synthesized and sintered at various temperatures by the SPS. The results show that the relative density of the ceramics prepared by the nanorod powders is higher than the density of the ceramics from the near-spherical powders after 600 °C due to the fracture and rearrangement of the nanorods at low temperatures, which leads to the decrease of particle size and the increase of density and homogeneity. Based on this novel densification mechanism, ultrafine-grained Y2O3 transparent ceramics with good optical and mechanical properties were fabricated successfully from the nanorod powders.

In this study, a multicolor-tunable Eu3+/Bi3+:Y2Zr2O7 transparent ceramic was successfully fabricated using vacuum sintering technology for the first time. The single-phase ceramic showed a pore-free structure and highest transmittance of 67% at 1200 nm. To reveal the luminescence properties of the obtained samples, photoluminescence (PL) tests were performed. Upon combining the green emission (centered at 475 nm) from Bi3+ and the red emission (centered at 629 nm) from Eu3+, bright, white light was observed in both the single-phase Eu3+/Bi3+:Y2Zr2O7 phosphors and transparent ceramics (λex = 302 nm). Furthermore, upon changing the excitation wavelengths, strong red (λex = 250 nm) and orange (λex = 365 nm) emissions were also observed at room temperature. The PL spectra and International Commission on illumination (CIE) coordinate diagram show that white light with CIE (0.3528, 0.3121) can be easily achieved. Combined with their excellent high-temperature performance and good mechanical properties, Eu3+/Bi3+:Y2Zr2O7 transparent ceramics have promising potential as white-light-emitting materials.

In this study, multi-walled carbon nanotubes (MWCNTs) are uniformly dispersed in aluminium nitride (AlN) powders, and the MWCNTs-doped AlN ceramics are sintered at 1500 °C with a holding time of 5 min by spark plasma sintering using Y2O3 as the sintering additive. The effects of the MWCNTs content on the microstructure and mechanical properties of the as-obtained ceramic composites are investigated. The results reveal that many submicron pores are generated when protecting the structure of the CNTs, thereby reducing the density of the AlN ceramic. However, the gradual filling of the grain gap may compensate for the strengthening after CNT doping. The relative density and hardness reach the maximum values of 89.6% of the theoretical density and 7.0 ± 0.3 GPa, respectively, at the doping amount of 2.5 wt%.

Herein, we report transparent LaGdZr2O7 nano-grained ceramics with an average grain size of 10 nm prepared using the high-pressure sintering method at 5.0 GPa/450 °C. These ceramics showed improved plastic deformation as compared to transparent micro-grained LaGdZr2O7 ceramics. Moreover, the fracture toughness of the nano-grained ceramics reached up to 3.4 MPam1/2, which is 79 % higher than that of the micro-grained samples. This improvement in the fracture toughness of the nano-grained ceramics was associated with the presence of a large number of weak grain boundaries in them.

Lithium titanium oxide (Li2TiO3) tritium breeder ceramic plates with nano- and coarse-grain size were fabricated. The preparation methods contained CTAB-modifying precursor, combining dry-pressing with isostatically cold-pressing, and calcinating at optimized sintering temperature in turn. Then their properties were characterized after radiation by 280 keV helium (He+) ion. Extensive characterization analyses were performed to reveal the changes in nano-grained and coarse-grained Li2TiO3 after radiation. They contained glancing angle X-ray diffraction (GIXRD), atomic force microscopy (AFM), electron spin resonance (ESR), and scanning electron microscopy (SEM). The results showed as follows, GIXRD peak position of the nano-grained Li2TiO3 was more stable than the coarse-grained Li2TiO3 after radiation. Nano-grained Li2TiO3 was less rough and swollen than the coarse-grained one after radiation. Nano-grained Li2TiO3 had more excellent structural stability and less defect concentration of Eʹ-center after radiation. As a result, nano-grained Li2TiO3 might have much better radiation tolerance than the coarse-grained one by comparing characterization results.

The Li4TiO4 ceramic is a promising solid-state tritium breeder material for the production of tritium fuel in the designs of fusion reactors. Tritium extraction efficiency is one of the key factors that determines the performance of the breeder material. Vacancies are known to trap tritium and adversely affect tritium extraction. Understandings of tritium-trapped defect configurations in Li4TiO4 are limited so far. In this work, the oxygen/lithium vacancy (VO/Li) and the vacancy-tritium defect complex (VO/Li + T) in Li4TiO4 are studied by first-principles density functional theory. The atomic configurations, formation energies and electronic structures of various charged defect species are obtained. We find that 2+ and 0 are the dominate charge states of VO, 1- is the dominate charge state of VLi, 1+ is the dominate charge state of the defect complex (VO + T), and 0 is the dominate charge state of (VLi + T). Tritium atoms trapped in VO are bonded to Ti atoms, and those trapped in VLi are bonded to O atoms.

Lanthanide-ion-based thermometers have been widely researched and utilized as contactless temperature sensing materials. Cooperating with the unique optical and excellent physical properties of transparent ceramics, Er

The exploration of new red phosphors is important for the development of white light-emitting diodes (w-LEDs), as existing red phosphors exhibit low efficiency and low performance. This work aims to enhance the photoluminescence characteristics of a red-emitting Gd2Zr2O7:Eu3+ phosphor by co-doping with Al3+. Eu3+ single-doped and Eu3+ and Al3+ co-doped Gd2Zr2O7 nanophosphors that could be efficiently pumped by commercial near-UV LED chips were prepared by a modified liquid–solid–solution phase-transfer method. X-ray diffraction data revealed that the synthesized phosphors were well crystallized with single-phase fluorite structure. Scanning electron microscopy images showed that the particle size ranges from 15 to 25 nm. In addition, the optical performance of the samples was characterized by fluorescence spectroscopy and lifetime spectroscopy. The effect of Al3+ on the luminescence performance of the Eu3+-doped Gd2Zr2O7 phosphor was studied in detail. The emission intensity of the Gd1.93Zr1·97O7:Eu3+0.07Al3+0.03 phosphor was found to be 620% stronger than that of the single-doped Eu3+ phosphor. These results unambiguously show that the Gd1.93Zr2-xO7:Eu3+0.07Al3+x phosphors are promising candidates for application in w-LEDs.

Creep behavior at room temperature was firstly observed in nanocrystalline Gd2Zr2O7 ceramic (NC-GZO) having an average grain size about 7.8 nm. The creep strain rate sensitivity of NC-GZO was calculated, and many dislocations can be observed in the strained region. The mechanism causing this room temperature creep behavior was associated with the dislocations slipping which most likely occurs though grain boundaries sliding.

A nitrate–citrate combustion method combined with microwave sintering was firstly employed for the rapid fabrication of the Gd2Zr2O7 matrix immobilizing various amounts of simulated nuclear wastes. Phase evolutions, microstructure changes, element distributions, densification processes and mechanical properties of the as-prepared (1 – x)Gd2Zr2O7·xTRPO (0.0 ≤ x ≤ 0.6) at various temperatures were investigated. Compared to the reported studies, we have increased the immobilization amount of simulated TRPO waste within a crystal structure from 45 to 60 wt%. Td and Tg (the threshold temperatures to trigger accelerated densification and grain growth, respectively) were employed to divide the densification process into three stages. the mechanical properties and the densification stages of the (1 – x)Gd2Zr2O7·xTRPO (0.0 ≤ x ≤ 0.6) ceramics sintered under microwave sintering at various temperatures were finally determined. Fine-grained (1 – x)Gd2Zr2O7·xTRPO (0.0 ≤ x ≤ 0.6) ceramic waste forms with average grain size less than 200 nm and relative density higher than 90% can be obtained by microwave sintering at sintering temperature less than 1400 °C.

Via a facile solid reactive method, transparent Ln0.1La0.9GdZr2O7 (Ln = Nd, Yb) ceramics were successfully fabricated for the first time. The highest in-line transmittances of Nd:LaGdZr2O7 and Yb:LaGdZr2O7 ceramics reached 68% and 69%, respectively, at 1100 nm. The microstructure and crystal structure of Ln0.1La0.9GdZr2O7 transparent ceramics were fully investigated, indicating that the solid reactive technique is a good method of industrially fabricating Ln0.1La0.9GdZr2O7 transparent ceramics. The PL spectra demonstrated that Ln0.1La0.9GdZr2O7 ceramics can effectively be excited at 808 nm and 976 nm, which correlates with the widely applied output wavelengths of AlGaAs and InGaAs laser diodes. The luminescence decay curves were also studied, showing that the average fluorescence lifetimes of Nd0.1La0.9GdZr2O7 and Yb0.1La0.9GdZr2O7 transparent ceramics was 355 μs and 663 μs, respectively. Combined with its high temperature resistance and good mechanical strength, Ln0.1La0.9GdZr2O7 (Ln = Nd, Yb) transparent ceramics can have potential applications in Nd/Yb solid-state laser construction.

We report a method combining the top-down and bottom-up approaches for the fabrication of nanocrystalline ceramic, which can break down the Y2O3 nanorods and consolidate the broken nanoparticles to 99.1% relative density. The lab-mad nanorods with a length of about 500 nm and a diameter of about 20 nm, exhibit better compressibility and sinterability than the spherical nanopowders when the compaction pressure exceeds 0.4 GPa and the sintering condition is 5 GPa/500 °C, respectively. The obtained nanocrystalline ceramic shows a maximum transmittance of 81.3% in the infrared region, hardness as high as 10.5 GPa and fracture toughness of 2.21 MPa m1/2.

Non-aqueous tape-casting forming technology was used in the fabrication of highly-transparent aluminum oxynitride (AlON) ceramics with different sizes and shapes. The tape-casting process utilizes the warm-pressing and the cold isostatic pressing methods, which can optimize the microstructure and increase the density of the AlON green tapes. In this work, highly-transparent AlON ceramics were fabricated by the pressureless sintering method at 1880 °C for 8 h. The transmittance of final polished AlON ceramic reaches 84 % at the wavelength of 2000 nm.

Translucent nanocrystalline Gadolinium Zirconate (Gd2Zr2O7) ceramic with grain size below 10 nm was successfully fabricated using high pressure sintering technology at 5 GPa and low temperature of 550 °C. The bilinear compressive stress-strain relationship of this sample was firstly extracted from nanoindentation procedure based on the partial unloading method. It indicated that the plastic deformation did not originate from dislocation sliding and was controlled by the grain boundary sliding. Moreover, the compressive yield strength, σ y = 7.8 GPa of the translucent nanocrystalline Gd2Zr2O7 ceramic was also determined by the intersection of the theoretical elastic line and the indentation compressive stress-strain line.

A novel mass production method of lithium titanite (Li2TiO3) tritium breeder ceramic pebbles using polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) assisted granulation method (APG) was proposed. A binder solution of polyvinyl alcohol (PVA) was used to modify the Li2TiO3 precursor powder. The powders with adhesive properties were prilled to form green pebbles (GPs) by spheronization at a low rotation speed and spraying with polyvinyl pyrrolidone (PVP), in several cycles. Then, the density and the crush load of the GPs were improved by high-speed rolling. Finally, the ceramic pebbles were produced by sintering. The phase, the microstructure, and the crush load of the ceramic pebbles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and with a universal tester, respectively.

Via a microwave annealing process, highly transparent U:Y2Zr2O7 ceramics were successfully fabricated for the first time. As-prepared powders obtained by microwave-assisted synthesis exhibited better particle distribution, grain fusion was inhibited at the same time. The near-infrared transmittance of U:Y2Zr2O7 transparent ceramic reached 80% at 2500 nm. And the cut-off wavelength of U:Y2Zr2O7 transparent ceramic moved from 250 nm to 540 nm, which was caused by the incorporation of the uranyl cation (UO2)2+. The ultraviolet light and visible light below 540 nm has been efficiently filtered to enhance the infrared imaging.

Synthesis of fine Li2TiO3 powders via low-temperature solid-state reaction (LTSSR) was studied. Solid Li2CO3 and H2TiO3 were blended by planetary ball mill with deionized water as medium. Calcination of the milled powder at low temperature of 500 °C resulted in the formation of pure Li2TiO3 nanoparticles. Another Li2TiO3 powder was also prepared by the conventional solid-state reaction (SSR) and a good comparison between different routes was realized. The results show that the particle size of LTSSR powder is significantly decreased to 19.6 nm while the one obtained by SSR is 146.6 nm. Low temperature calcined powders have less agglomeration and higher sinterability, which can be sintered at lower temperature. Pebbles sintered from the LTSSR powders at 750 °C exhibit small grain size (650 nm), high relative density (85.1%) and satisfactory crush load (42.8 N), whereas the SSR pebbles can only be sintered above 950 °C with the relative density close to 80%. Besides, the LTSSR samples also have a higher conductivity at room temperature, indicating the lower tritium diffusion barrier in ceramics. It is confirmed that H2TiO3 rather than TiO2 is more appropriate for the solid-state reaction to produce Li2TiO3 powders with nano-size particles and favorable properties.

A modified liquid–solid–solution (LSS) phase transfer method has been applied to synthesize Gd2Zr2O7 binary oxide nanoparticles. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) were employed to reveal the structural, morphological and energetic evolutions of both precursors and Gd2Zr2O7 nanoparticle products. The Gd2Zr2O7 nanoparticles synthesized using this method exhibit an average crystallite size of 1.7 nm, which have great potential to be applied in thermal barrier coatings (TBCs), solid oxide fuel cells (SOFCs) and nuclear waste immobilizations. Moreover, the method we developed in this study has a high Gd2Zr2O7 nanoparticle yield of up to 89%.