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  1. Abstract

    High‐entropy ceramics have been widely explored and extensively studied since the first demonstration of the configuration entropy stabilized reversible transitions between multiple and single phases by Rost et al. in 2015. Most of the current research on high‐entropy ceramics has focused on properties like thermal conductivity, thermoelectricity, structures, and others. Some recent studies have extended the high‐entropy concept to the field of transparent ceramics. We reviewed these papers and proposed four potential ceramics groups for high‐entropy transparent ceramics including fluoride ceramics, fluorite‐deficient and/or ordered pyrochlore A2B2O7ceramics, garnet ceramics, and sesquioxide ceramics. In this article, we review ceramic powder synthesis, the fabrication of transparent ceramics, high‐entropy ceramics, and limited cases of high‐entropy transparent ceramics for each category. High‐entropy transparent ceramics with diverse compositions and structures will provide more possibilities for functional transparent ceramics in the future.

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  2. Abstract

    For the first time, a transparent high‐entropy fluoride laser ceramic has been prepared and characterized. X‐ray diffraction (XRD) analysis of a CeNdCaSrBaF12(CNCSBF) transparent ceramic consolidated by vacuum hot pressing (VHP) reveals that Ce3+, Nd3+, Ca2+, Sr2+, and Ba2+have formed a single‐phased fluorite solid solution, with a lattice constant of 5.826 Å. Bulk density measurements produced a value of 6.15 g/cm3. Scanning electron microscopy (SEM) analysis of the ceramic revealed a uniform distribution of grain sizes in the material, with the average grain size being approximately 20 μm. The material exhibits a maximum in‐line transmittance of approximately 60% at 1000 nm. A near‐infrared range photoluminescence (PL) emission band was observed at 1057 nm, with a visible‐range PL emission band being located at 440 nm.

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  3. Abstract

    Transparent 1% Gd‐doped YAG and YAG ceramics were synthesized via solid‐state reaction spark plasma sintering using commercially available powder and TESO as a sintering additive. The highest in‐line transmission values achieved were 77.1% at 550 nm and 80.6% at 800 nm in the 1% (at.%) Gd‐doped YAG transparent ceramic with 99.90% relative density. Ultraviolet emission at 312.5 nm was observed in 1% Gd‐doped YAG ceramic via photoluminescence excitation, making it a promising material for applications in solid‐state UV devices.

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  4. Abstract

    Mixtures of Ce‐doped rare‐earth aluminum perovskites are drawing a significant amount of attention as potential scintillating devices. However, the synthesis of complex perovskite systems leads to many challenges. Designing the A‐site cations with an equiatomic ratio allows for the stabilization of a single‐crystal phase driven by an entropic regime. This work describes the synthesis of a highly epitaxial thin film of configurationally disordered rare‐earth aluminum perovskite oxide (La0.2Lu0.2Y0.2Gd0.2Ce0.2)AlO3and characterizes the structural and optical properties. The thin films exhibit three equivalent epitaxial domains having an orthorhombic structure resulting from monoclinic distortion of the perovskite cubic cell. An excitation of 286.5 nm from Gd3+and energy transfer to Ce3+with 405 nm emission are observed, which represents the potential for high‐energy conversion. These experimental results also offer the pathway to tunable optical properties of high‐entropy rare‐earth epitaxial perovskite films for a range of applications.

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  5. Abstract

    Sintering additives are generally considered to be important for improving densification in fabrication of transparent ceramics. However, the sintering aids as impurities doped in the laser materials would decrease the laser output power and produce additional heat during laser operation. In this work, Yb:YAG ceramics were vacuum‐sintered without additives at different temperatures for various soaking time through using ball‐milled powders synthesized by co‐precipitation route. The densification behavior and grain growth kinetics of Yb:YAG ceramics were systematically investigated through densification curves and microstructural characterizations. It was determined that the densification in the 1500°C‐1600°C temperature range was controlled by a grain‐boundary diffusion. It is revealed that the volume diffusion is the main mechanism controlling the grain growth between 1600°C and 1750°C. Although SiO2additives can promote densification during low‐temperature sintering, the optical transmittance of Yb:YAG ceramic with no additives, sintered at 1800°C for 15 hours, reaches a maximum of 83.4% at 1064 nm, very close to the measured transmittance value of Yb:YAG single crystal. The optical attenuation loss was measured at 1064 nm in Yb:YAG transparent ceramic, to be 0.0035 cm−1, a value close to that observed for single crystals.

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