Solid-State Reactions of a 3D-Transition Metal-Ti/Al 2 O 3 System
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Cu3Ti
,
0
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Cu3Ti3
,
Cu
(i)
The oxygen that reacts with the Cu-Ti intermetallic compounds arises through the reduction of the A12 0 3 substrate[2]. On the other hand, the presence of other Me3Ti 3 O-type compounds (Me= Mn, Fe, Co, Ni) has been reported[3]. Supposing that these compounds could be observed in other 3d-transition metal-Ti/Al 20 3 systems, the interfacial reactions of 3d-transition metal-Ti/Al 2 0 3 systems could be explained by the same mechanism. 557 Mat. Res. Soc. Symp. Proc. Vol. 318. c1994 Materials Research Society
In this study, the solid-state reactions of the Cu-Ti/A12 0 3 and Ni-Ti/A1 20 3 systems were examined for the purpose of identifying the solid-state reaction mechanism of the 3d-transition metal/Al 2 0 3 system. 2. EXPERIMENTAL PROCEDURE Thin Cu/Ti and Ni/Ti bilayer films were deposited on single crystals of A1203 using magnetron sputtering. Some Ni/Ti films were deposited on a Mo substrate. (Films do not react with a Mo substrate under the present experimental conditions. Hence, comparing the A1•0 3 substrate and the Mo substrate system indicates whether or not an interfacial reaction occurs between the films and the A120 3 substrate.) Sputtering was performed in an Ar atmosp ere of 6.7x10 Pa at room temperature after evacuating to 6.7x10 Pa. The compositions of the Cu-Ti films, which were calculated from each thickness, were 25at%Ti, 33at%Ti, and 50at%Ti. The compositions of the Ni-Ti films were 25at%Ti, 33at%Ti, 50at%Ti, and 66at%Ti. The total thickness of the films was fixed at 600 nm. After sputtering, the samples were placed in a vacuum furnace and heated-up from 873K to 1173K at a heating rate of 5K/min. Samples were held at the maximum temperature from 0 to 3600 s. After heat-treatment, the samples were cooled inside the furnace. The pressure in the furnace ranged from 6x10 to lxlO Pa during the heating process. The depth profiles of the composition of the samples were analyzed by AES, and the reaction products were examined by XRD. 3. RESULTS Cu-Ti/Al
93
system
three Cu-Ti sample, Cu-33at%Ti and Cu-50at%Ti In the intermetallic compounds, CuTi, Cu 4 Ti 3 , and CujTi, were observed after heat treatment at 873K. However, at 973K, only Cu 3Ti was 1), only Cu 3Ti was In the Cu-25at%Ti sample (Fig. observed. observed as a Cu-Ti intermetallic compound. At 973K, the peaks of Cu 3Ti decreased as heating progressed and were finally not Ti 20 peaks were observed under all experimental observed. conditions. Except in the case of heat-treatment at 873K for 0 s holding, peaks coinciding with peaks of the Me3Ti 3 O-type structure (diamond cubic of Fd3m) were observed. It was found that Cu 3Ti 30 compounds, which have a composition ranging from Cu2 Ti 4 O to CulTilO (the lattice constant varied from 1.124 to 1.144 nm), were formed in all samples after heat treatment at 973K. In the 33at%Ti sample the peaks of Cu3 Ti decreased as heating (Fig. 2), at 973K, progressed while those of the Cu 3Ti 3 O compound increased as heating progressed, and only the CuTi 30 compound and Cu were o
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