Grain-refining fabrication of nanocrystalline (La0.2Nd0.2Sm0.2Gd0.2Eu0.2)2Zr2O7 high-entropy ceramics by ultra-high pressure sintering
Grain-refining fabrication of nanocrystalline (La0.2Nd0.2Sm0.2Gd0.2Eu0.2)2Zr2O7 high-entropy ceramics by ultra-high pressure sintering
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DOI：
10.1016/j.jmst.2023.05.027
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发表时间：
2023
期刊：
影响因子：
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通讯作者：
Z. Wu;Wei Ji;Jinyong Zhang;Yanan Yuan;Ji Zou;Weimin Wang;Z. Fu
中科院分区：
文献类型：
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作者：
Z. Wu;Wei Ji;Jinyong Zhang;Yanan Yuan;Ji Zou;Weimin Wang;Z. Fu
(La0.2Nd0.2Sm0.2Gd0.2Eu0.2)2Zr2O7高熵烧绿石作为一种重要的A2B2O7型陶瓷，具有高熔点、高化学稳定性、低导热率等优良性能。然而，较低的烧结能力限制了其在热障涂层和放射性废物固定方面的应用。通常需要长期高温浸泡才能达到全密度，但不可避免地会出现晶粒长大。本工作采用超高压烧结（UHPS）方法，在10 GPa、800 ℃低温下制备了致密、晶粒细化的纳米晶（La0.2Nd0.2Sm0.2Gd0.2Eu0.2）2Zr2O7陶瓷。然后研究了 UHPS 处理样品的致密化行为、微观结构演变和性能。所制备的(La0.2Nd0.2Sm0.2Gd0.2Eu0.2)2Zr2O7陶瓷的晶粒尺寸仅为151 nm，比原料粉末的晶粒尺寸小40%。此外，它还表现出有利的性能，包括高硬度和水耐久性。超高压下的塑性变形被认为是导致晶粒细化和性能改善的主要致密化机制。
As an important A2B2O7-type ceramic, (La0.2Nd0.2Sm0.2Gd0.2Eu0.2)2Zr2O7high-entropy pyrochlore possesses promising properties such as high melting point, high chemical durability, and low thermal conductivity. However, the low sintering ability limits its application in thermal barrier coating and radioactive waste immobilization. It usually needs long-term high-temperature soaking to achieve full density, but with inevitable grain growth. In this work, dense and grain-refined nanocrystalline (La0.2Nd0.2Sm0.2Gd0.2Eu0.2)2Zr2O7ceramics were prepared with ultra-high pressure sintering (UHPS) method under 10 GPa at a low temperature of 800 °C. The densification behavior, microstructure evolution, and properties of the UHPS-ed samples were then investigated. The grain size of as-prepared (La0.2Nd0.2Sm0.2Gd0.2Eu0.2)2Zr2O7ceramic was only 151 nm, which is 40% smaller than that of raw powder. In addition, it exhibited advantageous properties including both high hardness and aqueous durability. Plastic deformation under ultra-high pressure was believed as the dominant densification mechanism responsible for grain refinement and property improvement.