doi:10.3850/978-981-08-6555-9_132


Sintered Reaction Bonded Silicon Nitride for Micro Mechanical Components


J. Rögner1, M. Müller2, K. -H. Lang1 and V. Schulze1,3

1Institute of Materials Science and Engineering I, Karlsruhe Institute of Technology, Karlsruhe, Germany

2Institute for Materials Research III, Karlsruhe Institute of Technology, Karlsruhe, Germany

3Institute of Production Science, Karlsruhe Institute of Technology, Karlsruhe, Germany

ABSTRACT

For the large-scale production of micro mechanical components which have to resist high loadings there is still a lack of adequate materials. Furthermore the geometrical accuracy of these components with structural details of about 10 µm is an important challenge for the material. The class of ceramics show excellent properties. In this paper the investigations on micro three point bending specimen made of sintered reaction bonded silicon nitride with varied feedstock composition (content of Y2O3, Al2O3, MgO and the specific surface of Si-powder) are described. The specimens were produced by hot moulding. For macroscopic specimen this material shows bending strengths between 500 and 1000 MPa, a sintering shrinkage of only 10 % and a relative density of about 95 and 100 %. When testing micro specimens the characteristic bending strength was found to be in the range of 540 to 1230 MPa. Due to the size effect a bending strength of about 860 – 1730 MPa was expected (provided that surface effect is active and the Weibull modulus is 12). The reasons for the lower bending strength were found to be: a lower relative density of about 80 % and a larger amount of secondary phase which is in part irregular dispersed. All micro specimens were tested as fired without a subsequent surface finishing.

Keywords: Silicon nitride, Mechanical properties, Micro specimen.


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