Effect of Current Density on the Microstructure and Mechanical Properties of 3YSZ/Al2O3 Composites by Flash Sintering

Abstract

The 3YSZ/40 wt% Al2O3 composites were prepared by flash sintering at a low furnace temperature (700 °C). The effects of the current density on the relative density and Vickers hardness of the composites were systematically investigated. The results showed that the relative densities and Vickers hardness of the samples increased gradually with the increasing of the current densities, and the relative density was as high as 94.2%. The Vickers hardness of 11.3 GPa was obtained under a current density of 102 mA/mm2. Joule heating and defects generation are suggested to be the main causes of rapid densification in flash sintering. The microstructure of the molten zone showed the formation of eutectic structures in the composite, suggesting that grain boundary overheating may have contributed to the formation of the molten zone.

Enhanced densification and ionic conductivity of LLZO by flash sintering

“…After flash sintering, the ceramics have an average size of less than 8 μm despite a very low number of intercrystalline pores. As current density increases during flash sintering, grain size increases slightly [45,51]. Smaller grain size in LLZO-1 compared to other flash-sintered samples may be caused by an inadequate current density, which does not stimulate diffusion and sintering properly.…”

Reactive Flash Sintering of Ceramics: A Review

“…[83] Later, eutectic microstructures were found in this same Al 2 O 3 -YAG system, [84,85] and also in Al 2 O 3 -ZrO 2 , [86] Al 2 O 3 -GdAlO 3 -ZrO 2 , [87] LaPO 4 -Al 2 O 3 , [88] and 3YSZ-Al 2 O 3 . [89] In the case of Al 2 O 3 -YAG, Liu et al [84] reported that the RFSed specimens exhibited better mechanical properties (e.g., hardness of 18.5 AE 0.3 GPa, and toughness of 4.3 AE 0.2 MPa m 1/2 ) than materials made by traditional directional solidification. Despite the excellent mechanical properties related to eutectic formation, many studies showed that eutectic microstructures were only found in current-localized areas during flash.…”

Mechanical properties of Al2O3–LaPO4 composites with eutectic microstructure produced by flash sintering

“…12,16,17 In the past, eutectic microstructures have been found in flash sintered ceramic composites including Al 2 O 3 and a combination of Y 3 Al 5 O 12 (YAG), 18,19 ZrO 2 , 17,20 GdAlO 3 , 21,22 or 3YSZ. 23 Traditionally, the mechanical properties of ceramic materials with eutectic microstructures often surpass those of corresponding conventional polycrystalline microstructures. [24][25][26] This improvement can be attributed to a variety of mechanisms that may enhance hardness, fracture toughness, and creep resistance compared with conventional polycrystalline microstructures.…”

“…Flash sintering methods can create heating and cooling conditions that satisfy the thermal gradient requirements, as well as lower the hardware requirements, therefore greatly facilitating the formation of eutectic microstructures 12,16,17 . In the past, eutectic microstructures have been found in flash sintered ceramic composites including Al 2 O 3 and a combination of Y 3 Al 5 O 12 (YAG), 18,19 ZrO 2 , 17,20 GdAlO 3 , 21,22 or 3YSZ 23 …”