高熵陶瓷(Zr_(1/7)Hf_(1/7)Ce_(1/7)Y2/7La_(2/7))O2-δ的制备及烧结行为

Preparation and Sintering Behavior of High-entropy Ceramic(Zr1/7Hf1/7Ce1/7Y2/7La2/7)O2-δ

近年来,不同体系的高熵陶瓷迅猛发展,但萤石结构高熵氧化物仍处于研发初期。本研究采用机械球磨和常压烧结的方法合成一种新型高熵萤石氧化物,利用XRD,SEM,TG-DSC和可视化形变分析仪研究了陶瓷的物相转变、表面形貌以及烧结行为。研究结果表明,(Zr_(1/7)Hf_(1/7)Ce_(1/7)Y2/7La_(2/7))O2-δ是一种非等摩尔的“高熵”陶瓷,其内部各元素分布均匀。湿法球磨和干法球磨制备的粉末结构和粒度均有所不同,单相转变温度为1600和1300℃,圆盘状坯体在1600℃保温1 h,尺寸收缩率约为8.5%和17.8%,致密度分别为82.25%和93.23%,说明球磨工艺是影响高熵陶瓷烧结的重要因素。此外,常压烧结制备(Zr_(1/7)Hf_(1/7)Ce_(1/7)Y2/7La_(2/7))O2-δ时,在1300~1600℃应适当减缓升温速率并延长保温时间,避免生坯收缩开裂,并提高陶瓷致密度。

High entropy ceramics(HECs)typically refer to a kind of solid solution consisting of five or more principal elements.In recent years,different kinds of HECs have developed rapidly whereas high entropy oxides with fluorite structure are still in their nascent state.In this study,a new type of high entropy fluorite oxide was successfully synthesized using mechanical ball-milling followed by conventional sintering.Phase transformation,surface morphology and sintering behavior of ceramic were characterized.The results demonstrate that(Zr_(1/7)Hf_(1/7)Ce_(1/7)Y2/7La_(2/7))O2-δis a non-equimolar high entropy ceramic in which all elements distribute homogenously.The powders derived from wet-milling or dry-milling possess different crystal structure and particle size.Raw materials transform into single-phase structure at 1600℃and 1300℃,respectively.After dwelling at 1600℃for 1 h,the shrinkage of two discs are 8.5%and 17.8%,approximately,at the same time,the relative densities are 82.25%and 93.23%.These miscellaneous distinctions indicate that ball-milling process is a crucial factor affecting sinterability of HECs.In order to avoid cracks caused by rapid shrinkage and improve density of ceramic,it is vital to decrease heating rate and prolong dwell time in the range of 1300-1600℃as preparing(Zr_(1/7)Hf_(1/7)Ce_(1/7)Y2/7La_(2/7))O2-δby conventional sintering.