An object of the present invention is to provide a quartz resonator unit and a quartz oscillator having a small size and a light weight and having the capability of oscillating in the overtone mode, and also to provide a quartz element for use in the quartz resonator unit and quartz oscillator. Thus, a further object is to determine the optimum width-to-thickness ratio of the quartz element at which the quartz element having a width less than 1.5 mm and a length less than 4.7 mm does not show coupling with spurious vibrations over the entire range of operation temperature. From the experiments and evaluation performed repeatedly, it has been concluded that an AT-cut rectangular quartz element having the width-to-thickness ratio w/t in a range selected from the group consisting of 8.48 0.05, 12.18+/-0.05, 13.22+/-0.07, 14.78+/-0.07, and 15.57 0.07 is suitable as a small-sized quartz element that can oscillate at a high frequency and has excellent temperature characteristics. There are also disclosed important factors to obtain a quartz element having a low resonance resistance.
This is a Continuation of application Ser. No. 08/454,305 filed Aug. 17, 1995 now abandoned, which in turn is a U.S. National Stage Application of PCT/JP94/01721 filed Oct. 13, 1994.
