稀土氧化物对常压烧结氮化硅陶瓷性能的影响

doi:10.15541/jim20170056

摘要/Abstract

摘要：

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。

关键词: 稀土氧化物, 氮化硅, 热导率, 常压烧结

Abstract:

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.

Key words: rare earth oxide, silicon nitride, thermal conductivity, pressureless sintering

中图分类号:

TQ174

段于森, 张景贤, 李晓光, 黄鸣鸣, 施鹰, 谢建军, 江东亮. 稀土氧化物对常压烧结氮化硅陶瓷性能的影响[J]. 无机材料学报, 2017, 32(12): 1275-1279.

DUAN Yu-Sen, ZHANG Jing-Xian, LI Xiao-Guang, HUANG Ming-Ming, SHI Ying, XIE Jian-Jun, JIANG Dong-Liang. Rare Earth Oxides on Property of Pressureless Sintered Si₃N₄ Ceramics[J]. Journal of Inorganic Materials, 2017, 32(12): 1275-1279.

图/表 8

表1 烧结助剂中稀土氧化物和氧化钛质量比

Table 1 The mass ratio of Re2O3 to TiO2

	Sm₂O₃:TiO₂(ST)	Er₂O₃:TiO₂(ET)	Lu₂O₃:TiO₂(LT)
Mass ratio	2:1	1:1	1:1

图1 Si3N4陶瓷密度随烧结助剂种类和含量的变化

Fig. 1 Variation of density of Si3N4 ceramics with different type and content of sintering additives

表2 稀土离子半径, 电负性及熔点

Table 2 Ion radius, electronegativity and melting point of rare earth elements

Element	Sm	Er	Lu
Atomic number	62	68	71
Re³⁺radius/pm	95.8	89.0	86.1
Electronegaticity	1.17	1.24	1.27
T_M of Re₂O₃/℃	2262	2387	2510

图2 添加不同烧结助剂Si3N4陶瓷的XRD图谱(烧结助剂含量均为8wt%)(a)和不同含量ST样品的XRD图谱(b)

Fig. 2 XRD patterns of Si3N4 ceramics with different sintering additives type (the sintering additives content was 8wt%) (a) and Si3N4 ceramics with different sintering additive contents (the sintering additive was Sm2O3-TiO2)(b)

表3 β-Si3N4和TiN两相质量比

Table 3 Mass ratio of β-Si3N4 to TiN

	ST-1	ST-2	ST-3	ST-4
W_β-Si3N4/W_TiN	—	57.8	40.6	30.2

图3 Si3N4陶瓷热导率随烧结助剂种类和含量的变化

Fig. 3 Variation of thermal conductivity of Si3N4 ceramic with different sintering additives type and content

图4 不同烧结助剂得到的Si3N4陶瓷(a)LT-3和(b) ET-3显微结构图

Fig. 4 Microstructures of Si3N4 ceramic (a)LT-3 and (b)ET-3 with different sintering additives

表4 不同烧结助剂制备的Si3N4陶瓷的力学性能以及热处理后热导率的变化

Table 4 Mechanical properties of Si3N4 ceramic with different sintering additives and the corresponding thermal conductivity value after annealing at 1600℃ for 8 h

Sample	Fracture toughness/ (MPa•m^1/2)	Hardness/ GPa	Thermal conductivity after annealing/ (W∙m^-1∙K^-1)
LT-3	5.29	10.8	45.3
ET-3	5.46	12.2	51.8
ST-3	5.76	11.7	40.8

参考文献 19

[1]	YOU ZHOU, HIDEKI HYUGA, DAI KUSANO, et al.Development of high-thermal-conductivity silicon nitride ceramics. Journal of Asian Ceramic Society, 2015, 3(3): 221-229.
[2]	XU PENG, YANG JIAN, QIU TAI, et al.Research progress of β-Si3N4 ceramics with high thermal conductivity. Bulletin of the Chinese Ceramic Society, 2010, 29(2): 384-389.
[3]	HAGGERTY J S, LIGHTFOOT A.Opportunities for enhancing the thermal conductivities of SiC and Si3N4 ceramics through improved processing. Ceramic Engineering & Science Proceedings, 1995: 475-487.
[4]	KIYOSHI HIRAO, YOU ZHOU, HIDEKI HYUGA, et al.High thermal conductivity silicon nitride ceramics. Journal of the Korean Ceramic Society, 2001, 26(6): 451-455.
[5]	ZHOU YOU, HYUGA HIDEKI, KUSANO DAI, et al.A tough silicon nitride ceramic with high thermal conductivity. Advanced Materials, 2011, 23(39): 4563-4567.
[6]	ZHU XIN-WEN, SAKKA YOSHIO.Textured silicon nitride: processing and anisotropic properties. Science and Technology of Advanced Materials, 2008, 9(3): 033001.
[7]	MIKITO KITAYAMA, KIYOSHI HIRAO, KOJI WATARI, et al.Thermal conductivity of β-Si3N4-III, effect of rare-earth (RE = La, Nd, Gd, Y, Yb, and Sc) oxide additives. Journal of the AmericanCeramic Society, 2001, 84(2): 353-358.
[8]	LEE SEA-HOON.Densification, mass loss, and mechanical properties of low-temperature pressureless-sintered Si3N4 with LiYO2 additive: the effects of additive content and annealing. International Journal of Applied Ceramic Technology, 2010, 6(7): 881-888.
[9]	MATOVIC B, RIXECKER G, GOLCZEWSKI J, et al.Thermal conductivity of pressureless sintered silicon nitride materials with LiYO2 additive. Science of Sintering, 2004, 36: 3-9.
[10]	YANG HAI-TAO, GAO LING, YUAN RUN-ZHAN.Effect of MgO-CeO2 on pressureless sintering of silicon nitridea. Materials Chemistry and Physics, 2001, 69: 281-283.
[11]	GAO LING, YANG HAI-TAO, YUAN RUN-ZHANG, et al.Sintering and microstructure of silicon nitride with magnesia and cerium additives. Journal of Materials Processing Technology, 2001, 115: 298-301.
[12]	NAOKI KONDO, MIKINORI HOTTA, TATSUKI OHJI.Low-cost silicon nitride from β-silicon nitride powder and by low-temperature sintering. International Journal of Applied Ceramic Technology, 2015, 12(2): 377-382.
[13]	GUO WEI-MING., WU LI-XIANG, MA TI, et al.Rapid fabrication of Si3N4 ceramics by reaction-bonding and pressureless sintering. Journal of the European Ceramic Society, 2016, 36: 3919-3924.
[14]	ZHU XIN-WEN, ZHOU YOU, HIRAO KIYOSHI, et al.Potential use of only Yb2O3 in producing dense Si3N4 ceramics with high thermal conductivity by gas pressure sintering. Science and Technology of Advanced Materials, 2010, 11(6): 1-12.
[15]	WANG ZH, BAI B, NING XS.Effect of rare earth additives on properties of silicon nitride ceramics. Advances in Applied Ceramics, 2014, 133(3): 173-177.
[16]	MIKITO KITAYAMA, KIYOSHI HIRAO, SHUZO KANZAKI.Effect of rare earth oxide additives on the phase transformation rates of Si3N4. Journal of the American Ceramic Society, 2006, 89(8): 2612-2618.
[17]	ZHANG JIE, NING XIAO-SHAN, LUE XIN, et al.Effect of rare-earth additives on thermal conductivity, mechanical and electrical properties of silicon nitride ceramics. Rare Metal Materials and Engineering, 2008, 37(1): 693-696.
[18]	LU XIN, NING XIAO-SHAN, XU WEI, et al.Effect of CeO2, Dy2O3, Yb2O3 and Y2O3 additives on thermal conductivity of silicon nitride ceramics. Rare Metal Materials and Engineering, 2005, 34(24): 1112-1114.
[19]	WANG HUI-PING, ZHOU SHU-ZHU.Carbothermic reduction of TiO2 in N2 atmosphere-A study for direct compounding TiCN solid solution. Rare Metals and Cemented Carbides, 1996(127): 25-29.