Transparent ceramics have various potential applications such as infrared (IR) windows/domes, lamp envelopes, opto-electric components/devices, composite armors, and screens for smartphones and they can be used as host materials for solid-state lasers. Transparent ceramics were initially developed to replace single crystals because of their simple processing route, variability in composition, high yield productivity, and shape control, among other factors. Optical transparency is one of the most important properties of transparent ceramics. In order to achieve transparency, ceramics must have highly symmetric crystal structures; therefore, the majority of the transparent ceramics have cubic structures, while tetragonal and hexagonal structures have also been reported in the open literature. Moreover, the optical transparency of ceramics is determined by their purity and density; the production of high-purity ceramics requires high-purity starting materials, and the production of high-density ceramics requires sophisticated sintering techniques and optimized sintering aids. Furthermore, specific mechanical properties are required for some applications, such as window materials and composite armor. This review aims to summarize recent progress in the fabrication and application of various transparent ceramics.

Materials development and potential applications of transparent ceramics: A review

Rare earth zirconate nanostructures: Recent development on preparation and photocatalytic applications

A2B2O7 system compounds, which usually present three phase structures mainly based on the ionic radius ratios of rA and rB (rA/rB), have been studied for potential applications in many fields, such as thermal barrier coatings, luminescence powders, fast-ion conductors, photocatalysts, and matrices for immobilization of highly active radionuclides. Since 2005, La2Hf2O7 was fabricated into transparent ceramics and much more attentions were paid on A2B2O7 transparent ceramics for new applications. In this review, the development of A2B2O7 system transparent ceramics was described. The structure characteristics, powder synthesis method, and sintering techniques of the final A2B2O7 transparent ceramics were summarized. After that, the mostly reported A2Hf2O7, A2Zr2O7, and A2Ti2O7 system transparent ceramics were systematically introduced. The potential application fields and future development trends were also discussed, focusing on scintillators, optical elements, and other luminescent materials

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Recent development of A2B2O7 system transparent ceramics

Metal oxide nanoparticles demonstrate uniqueness in various technical applications due to their suitable physiochemical properties. In particular, yttrium oxide (Y2O3) nanoparticle is familiar for technical applications because of its higher dielectric constant and thermal stability. It is widely used as a host material for a variety of rare-earth dopants, biological imaging, and photodynamic therapies. Y2O3 has also been used as a polarizer, phosphor, laser host material, and in the optoelectronic fields for cancer therapy, biosensor, and bioimaging. Yttrium oxide nanoparticles have attractive antibacterial and antioxidant properties. This review focuses on the promising applications of Y2O3, its drawbacks, and its modifications. The synthetic methods of nanoparticles, such as sol-gel, emulsion, chemical methods, solid-state reactions, combustion, colloid reaction techniques, and hydrothermal processing, are recapitulated. Herein, we also discuss the advantages and disadvantages of Y2O3 NPs based biosensors that function through various detection modes including colorimetric, electrochemistry, and chemo luminescent regarding the detection of small organic chemicals, metal ions, and biomarkers.

Yttrium Oxide Nanoparticle Synthesis: An Overview of Methods of Preparation and Biomedical Applications

The design and development of efficient and stable nuclear waste hosts has drawn intensive interest for long-lived lanthanides and actinides. A detailed investigation of their structure and potential structural evolution are crucial. In this study, we have synthesized lanthanum hafnate La2Hf2O7 nanoparticles (NPs) doped with uranium at different concentrations (0–10%) and investigated their structural transition. We have discovered that in our La2Hf2O7:U NPs, the uranium dopants are stabilized at both U4+ and U6+ oxidation states in which the U6+ oxidation state exists in octahedral uranate UO66− form. We also confirmed that the U4+ ions substituted the Hf4+ ions with a lifetime of ∼1.0 μs and the UO66− ions resided at the La3+ sites with a lifetime of ∼9.0 μs. More interestingly, the proportion of the U4+ ions in the La2Hf2O7:U NPs was higher than that of the UO66− ions at low doping level, but at the doping level higher than 2.5%, the fraction of the UO66− ions was greater than that of the U4+ ions. Furthermore, we studied the structural phase transformation from order pyrochlore to cotunnite of these La2Hf2O7:U NPs with increasing uranium doping level, and found that ordered pyrochlore phase favors the U4+ ions whereas disordered cotunnite phase favors the UO66− ions. We further used in situ Raman spectroscopy to confirm the reversible cotunnite to pyrochlore phase transformation of the La2Hf2O7:10%U NPs at 900 °C. Therefore, this work demonstrated the successful development of uranium doped La2Hf2O7 NPs and thorough characterization of the fundamental spectra of uranium ions, doping induced phase transformation, and structure–optical property correlation.

On structure and phase transformation of uranium doped La2Hf2O7 nanoparticles as an efficient nuclear waste host

A simple combustion method was used to synthesize LaGdZr2O7 powder and LaGdZr2O7 transparent ceramic was prepared by vacuum sintering at 1850 °C for 6 h. The final transparent ceramic, with a density of 6.46 g/cm3, has an in-line transmittance of 70.7% at 1000 nm and a refractive index of 2.08 at 632.8 nm.

Fabrication of LaGdZr2O7 transparent ceramic

Y2Zr2O7 transparent ceramic was successfully fabricated from combustion-synthesized powders. The as-prepared Y2Zr2O7 powders were characterized by XRD, FE-SEM, TEM, and BET area. After high-energy ball milling, the porous structure of the powder was destroyed. The Y2Zr2O7 transparent ceramics were obtained by sintering the ball-milled powders at 1850°C for 6 h in vacuum. Ball milling of the as-burnt powders was found to play a key role on the in-line transmittance of the resultant ceramic.

Fabrication of Transparent Y2Zr2O7 Ceramics from Combustion‐Synthesized Powders

Transparent La2−xGdxZr2O7 ceramics obtained by combustion method and vacuum sintering

Fabrication of transparent Y2Hf2O7 ceramics via vacuum sintering

http://faculty.uscupstate.edu/cbender/web%20page%20folder%20enmass/chm%20397/control%20of%20particle%20shape%20with%20surfactant.pdf

Guangjun Zhang

Papers

Fabrication of LaGdZr2O7 transparent ceramic

Fabrication of Transparent Y2Zr2O7 Ceramics from Combustion‐Synthesized Powders

Transparent La2−xGdxZr2O7 ceramics obtained by combustion method and vacuum sintering

Fabrication of transparent Y2Hf2O7 ceramics via vacuum sintering

Morphology-controlled synthesis of yttrium hafnate by oxalate co-precipitation method and the growth mechanism