稀土氧化物对常压烧结氮化硅陶瓷性能的影响

高导热氮化硅陶瓷是大功率电力电子器件散热的关键候选材料。研究采用稀土氧化物(Re₂O₃)和氧化钛(TiO₂)烧结助剂体系, 通过低温常压烧结方法来制备氮化硅陶瓷, 以有效降低成本, 满足实际应用的需求。系统研究了烧结助剂种类及含量对Si₃N₄陶瓷的致密化行为、热导率、显微结构以及力学性能的影响。研究发现随着稀土离子半径的增大, 材料的致密度和热导率均呈现下降趋势, 添加Sm₂O₃后样品最高密度仅为3.14 g/cm³。但是当Sm₂O₃-TiO₂烧结助剂含量为8wt%时, 样品断裂韧性可达5.76 MPa?m^1/2。当添加Lu₂O₃且烧结助剂含量为12wt%时, 材料的密度可达3.28 g/cm³, 但是大量存在的第二相导致热导率仅为42.3 W/(m?K)。研究发现该材料具有良好的断裂韧性。经1600℃退火8 h后, Er₂O₃-TiO₂烧结助剂样品的热导率达到51.8 W/(m?K), 基本满足一些功率电路基板材料的实际应用需求。

Rare Earth Oxides on Property of Pressureless Sintered Si3N4 Ceramics

High thermal conductivity Si₃N₄ ceramic is a prospective substrate material for high-power electronic devices. In this paper, pressureless and liquid-phase sintering was proposed using Re₂O₃ (Re=Sm, Er, Lu) - TiO₂ as sintering additives to effectively reduce the cost for applications. Effect of the additive type and content on microstructure, mechanical properties and thermal conductivity of the ceramic were investigated. Results showed that the relative density, thermal conductivity and grain size of Si₃N₄ decrease gradually with the increase of Re ionic (Re³⁺) radius. With addition of Sm₂O₃, the highest density can only reach 3.14 g/cm³, while the fracture toughness about 5.76 MPa?m^1/2 can be obtained when 8wt% Sm₂O₃-TiO₂ is used. With 12wt% Lu₂O₃-TiO₂ as sintering aid, Si₃N₄ ceramics show high density of 3.28 g/cm³ as well as high fracture toughness, while the thermal conductivity is only 42 W/(m?K) due to the presence of large amount of second phase. Thermal conductivity of Si₃N₄ reaches 51.8 W/(m?K) with the addition of 8wt% Er₂O₃-TiO₂, which can meet the requirement for substrate materials for power electronic device.