| 摘要 |
PROBLEM TO BE SOLVED: To improve environmental resistance by disposing an excitation electrode on the surface of a piezoelectric substrate which has Langasite crystal structure and contains at least lanthanum, gallium, and silicon, and specifying the silicon density of the surface of the substrate. SOLUTION: La3Ga5.5Nb0.5O14 single crystal and SiO2 are mixed and fused in a high-frequency single-crystal growing furnace and seed crystal is brought into contact with the surface of the fused liquid to obtain Langasite single crystal. A surface ofϕ=100 deg.,θ=145 deg., andψ=145 deg. in Euler-angle presentation is cut out of the single crystal, and lapped and polished to obtain a Langasite substrate. An EPMA analysis of the polished surface is taken to measure the silicon density. Here, the silicon density is so controlled that the silicon density of the substrate surface is within a range of 0.3 to 1.0 atomic %. Input/output side excitation electrodes 2a and 2b are formed on the surface 1a of the substrate 1 which is thus obtained.
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