Combinatorial Searching for Pt-Zr-Ni Thin Film Amorphous Alloys for Glass Lens Mold
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1024-A06-08
Combinatorial Searching for Pt-Zr-Ni Thin Film Amorphous Alloys for Glass Lens Mold Mitsuhiro ABE1, Seiichi HATA2, Ryusuke YAMAUCHI1, Junpei SAKURAI1, and Akira SHIMOKOHBE1 1 Precision and Intelligence Laboratory, Tokyo Institute of Technology, R2-37 4259 Nagatsuta Midori-ku, Yokohama, 226-8503, Japan 2 Frontier Collaborative Research Center, Tokyo Institute of Technology, S2-8 4259 Nagatsuta Midori-ku, Yokohama, 226-8503, Japan ABSTRACT New compositions of Pt-Zr-Ni thin film amorphous alloys, as materials for glass lens molds, were searched by combinatorial arc plasma deposition (CAPD). Firstly, 3,267 samples were deposited by CAPD. Of these, 312 amorphous compositions were found. In the amorphous composition region, three typical amorphous samples that were expected to have a high crystallization temperature (Tx) were deposited by sputtering, because the CAPD samples were too small for the evaluation of Tx and mechanical strength by conventional methods. Finally, Pt50Zr36Ni14, with a high Tx of 985 K, a high σf of 2.12 GPa and low adherence to molten glass was discovered as a new material for use as a glass lens mold. INTRODUCTION Combinatorial technology has drawn attention as a new efficient method for searching new materials and for the optimization of physical properties. We have developed a combinatorial arc plasma deposition method (CAPD) as a new combinatorial deposition method [1]. The CAPD method has been applied for the search of new thin film amorphous alloys [2]. Amorphous alloys are suitable for minute, precision mold materials, because they have a homogeneous and isotropic structure and do not show size effect caused by grains and grain boundaries. The physical properties of amorphous alloys can be adjusted by changing the constituent elements and composition [2]. CAPD was used to search for new mold materials for an optical lens. Plastic lens molds have been successfully fabricated with a diffraction grating using a Pd-Cu-Si amorphous thin film [3]. The amorphous thin film was sputter-deposited on the surface of a blank mold, and was then cut to fabricate an optical surface and diffraction grating. However, Pd-Cu-Si system amorphous alloys cannot be used as a material for a glass lens mold, because the crystallization temperature (Tx) is lower than the molding temperature of the glass lens [2]. In order to use an amorphous alloy as a glass lens mold material, new amorphous alloys with the following target properties must be found: 1) High crystallization temperature, Tx: In this study, BK7 (Schott AG) was employed as the glass material, the Tg of which is 830 K. Therefore, it was determined that the target Tx of the amorphous alloy should exceed 973 K, that is, over 100 K larger than the Tg of BK7. 2) High mechanical strength: To prevent the microstructure of the mold from being destroyed during molding, the target amorphous alloy must have high compressive strength. However, in this study, the tensile
strength was evaluated as mechanical strength, because it is difficult to measure t
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