Author: Shiao Wu ^ab1, Yang Li ^b1, Yueming Li ^c, Fuyuan Zheng ^b, Zhongyi Zhao ^a, Xiangqing Kong ^d, Guorui Zhao ^b

Journal: Vacuum

DOI: https://doi.org/10.1016/j.vacuum.2025.114402Get rights and content

Abstract / 摘要

Preparation Si₃N₄ ceramics with high hardness and high fracture toughness is a challenge. In this work, Si₃N₄ ceramics with high hardness (18.35 ± 0.40 GPa) and high fracture toughness (8.54 ± 0.26 MPa m^1/2) were obtained by in-situ nitriding of Si and Y powders and hot-press sintering. By controlling Y content, Si₃N₄ powders with different α-Si₃N₄ ratios were obtained, which in turn regulated grain size and morphology of Si₃N₄ ceramics after sintering. Addition of Y introduces Y-Si-O-N crystalline phase into nitrided powder, which transitions to Y₂Si₂O₇ during subsequent sintering. Y₂Si₂O₇ phase reduces bulk hardness but introduces residual stresses at interface, promotes grain elongation, and improves fracture toughness through crack bridging, stretching, and crack deflection mechanisms. In addition, atomic-scale microstructural analysis reveals coherent interfaces were formed between both Si₃N₄/SiO₂/Y₂Si₂O₇ as well as Si₃N₄/Si₂N₂O, with crystallographic orientation relationships of (100) Si₃N₄//(100) SiO₂//(−111) Y₂Si₂O₇ and [010] Si₃N₄//[001] SiO₂//[12–1] Y₂Si₂O₇ as well as (100) Si₃N₄//(020) Si₂N₂O and [010] Si₃N₄//[−102] Si₂N₂O. These in-situ generated coherent interfaces significantly enhance mechanical properties and reliability of samples, ensuring both high hardness and high fracture toughness.

Keywords / 关键词

Si₃N₄; Nitridation process; Hot-press sintering; Mechanical properties