Microstructure of Spark Plasma-Sintered Silicon Nitride Ceramics

Abstract

The microstructure and phase composition of the high-content Al2O3-Y2O3-doped spark plasma-sintered silicon nitride were investigated. Fully dense silicon nitride ceramics with a typical α-Si3N4 equiaxed structure with average grain size from 200 to 530 nm, high elastic modulus of 288 GPa, and high hardness of 2038 HV were spark plasma sintered (SPSed) at 1550 °C. Silicon nitride with elongated β-Si3N4 grains, higher hardness of 1800 HV, density of 3.25 g/cm3, and Young’s modulus 300 GPa SPSed at 1650 °C was also reviewed.

Improved mechanical properties of dense β-Si3N4 ceramics fabricated by spark plasma sintering with Al2O3-YSZ additives

“…On the other hand, the slightly lower Vickers hardness but much higher fracture toughness in the sample SPSed at 1600°C is due to the sample's pure β-Si 3 N 4 phase having strong bonding strength with the glass formed by Al 2 O 3 and YSZ additives. It is known that the hardness of α-Si 3 N 4 is higher than that of β-Si 3 N 4[24], while β-Si 3 N 4 phase shows better fracture toughness[10]. The sample SPSed at 1600°C for 15 min using Al 2 O 3 and yttria-stabilized zirconia additives shows relatively good mechanical properties with Vickers hardness of 16.13 GPa and fracture toughness of 6.75 MPa m 1/2 as compared to other literature reports.…”

“…This density is higher than reported in relative literature. Thus, it is reported that the density of 3.25 g/cm 3 of Si 3 N 4 ceramics was obtained by SPS using 9.0 wt.% Al 2 O 3 and 6.0 wt.% Y 2 O 3 additives at 1650°C for 10 min [24]. The silicon nitride ceramics obtained by SPS with a density of 3.08 g/cm 3 sintered at 1500°C, 3.23 g/cm 3 sintered at 1600°C and also 3.23 g/cm 3 sintered at 1650°C, by using 2.0 wt.% Al 2 O 3 and 5.0 wt.% Y 2 O 3 additive was also reported [25].…”

Glass-Ceramics Processed by Spark Plasma Sintering (SPS) for Optical Applications

“…The technique appears like HP heated by a radiative furnace. However, the SPS treated samples can reach relevant qualities like structurally tailoring effect, grain growth control, enhancement of electro-migration, and strong preferential orientation effect [2,8].…”

“…In the OFF mode, plasma passes throughout the volume of the sintered powder, followed by vaporization, melting of surface, and neck formation. The large pulse energy generates an electromagnetic field effect, such as an electro-migration and preferential orientation of the crystalline phase [8,38]. The sintering mechanism of nano grained (NG-YAG) ceramics at high pressure was proposed by Wang et al [39].…”

“…The high-content Al 2 O 3 -Y 2 O 3 -doped SPS-sintered silicon nitride was investigated by O.A. Lukianova1 et al [8]. Fully dense silicon nitride ceramics with the main phase of α-Si 3 N 4 equiaxed hexagonal grained microstructures were obtained.…”