| 摘要 |
PROBLEM TO BE SOLVED: To obtain a light-transmittable ceramic of high mechanical strength with high corrosion resistance, not getting opaque even if used in arc tubes using rare earth metal halide, by specifying the total content of Tm, Yb and Lu in the rare earth elements of the corrosion-resistant rare earth aluminum garnet ceramic, the Si content of the ceramic, and the total content of Ca and Mg in the ceramic. SOLUTION: This ceramic is such one that the total content of Tm, Yb and Lu in the rare earth elements is 10-100 mol% (pref. 10-50 mol%), the Si content of this ceramic and the total content of Ca and Mg in this ceramic are 0-100 ppm and 0-200 ppm, respectively, on a metal bases. This ceramic has an average particle size of 1-20μm, average flexural strength of >=400 MPa, and Weibull modulus of >=6. In this ceramic, one surface of the ceramic matrix bears a corrosion-resistant garnet film made up of at least one member of Tm, Yb, and Lu both the matrix and corrosion-resistant garnet film being light-transmittable. An arc tube for high-pressure discharge lamps is obtained by providing the corrosion-resistant film inside the ceramic matrix. This ceramic is inexpensive and dispenses with the specular polishing of the inner face of high-pressure discharge lamps.
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