| 摘要 |
A crystal oscillator unit which serves as a flat packaged piezoelectric device includes a base member, a quartz piece, and a cap member sealed air-tight to the base member to enclose the quartz piece in cooperation with the base member. Each of the base and the cap members is made of a glass-ceramic composite material in which 30 to 70% by weight of forsterite is dispersed in glass and which has a thermal expansion coefficient between 100x10-7/ DEG C. and 150x10-7/ DEG C. The glass consists, in percent by weight, essentially of 50 to 70% of SiO2, 3 to 15% of Al2O3, 0 to 10% of ZnO, 0 to 8% of B2O3, 7 to 25% of at least one member of CaO, SrO, and BaO, and 13 to 27% of at least one member of Na2O, K2O, and Li2O. The glass and the forsterite are pulverized to an average particle diameter of 1 to 3 microns, mixed together with addition of fine powder of an average particle diameter of 0.1 to 1 micron of 0 to 5% by weight of at least one member of ZrO2, TiO2, SnO2, P2O5, and MoO3, and sintered at a temperature between 800 DEG C. and 1000 DEG C.
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