Numéro
J. Phys. IV France
Volume 03, Numéro C7, Novembre 1993
The 3rd European Conference on Advanced Materials and Processes
Troisiéme Conférence Européenne sur les Matériaux et les Procédés Avancés
Page(s) C7-1393 - C7-1397
DOI http://dx.doi.org/10.1051/jp4:19937213
The 3rd European Conference on Advanced Materials and Processes
Troisiéme Conférence Européenne sur les Matériaux et les Procédés Avancés

J. Phys. IV France 03 (1993) C7-1393-C7-1397

DOI: 10.1051/jp4:19937213

Influence of Si3N4 interface chemistry on both grain morphology and fracture resistance

H.-J. KLEEBE, E. MEISSNER and G. ZIEGLER

University of Bayreuth, Institute of Materials Research (IMA), Postfach 10 12 51, 95440 Bayreuth, Germany


Abstract
Quantitative microstructural analysis was performed on Si3N4 materials doped with 5 wt% Y2O3 and 5 wt% Sc2O3 as sintering aids. Two different processing routes were utilized to achieve complete densification : (i) gas-pressure sintering of Si3N4-starting powders (SSN) and (ii) post-sintering of reaction-bonded Si3N4 (SRBSN). Apart from quantitative evaluation of grain diameter and aspect ratio of the matrix grains, the fracture toughness was determined. While the two Y2O3-doped materials (SSN, SRBSN) showed identical KIC-values, a large discrepancy in fracture toughness was found for the Sc2O3-doped Si3N4 (ΔKIC = 5 MPa√m). SEM crack propagation studies and additional TEM interface characterization showed no signifïcant difference between these materials. Quantitative microstructure analysis, however, revealed a pronounced variation in grain diameter and aspect ratio after thermal treatment. A correlation between interface chemistry and both resulting microstructure and fracture resistance is discussed.



© EDP Sciences 1993