GB1058199A - Piezoelectric resonators - Google Patents

Abstract

1,058,199. Piezo-electric devices. CLEVITE CORPORATION. May 19, 1964 [May 20, 1963], No. 20686/64. Heading H1E. A Piezo-electric resonator comprises a thin wafer 30 of piezo-electric material having an inner region " a " and an outer region " b " of the same piezo-electric or different material surrounding the inner region " a ", the outer region having a higher resonant frequency than the inner region (b inner: b outer equals 0À8- 0À999), and so acting as a cut-off for the resonant frequency of the inner region. Several resonators " a " may be mounted, uncoupled, on the same wafer 30. The inner regions " a " may be formed: by depositing a layer of material, e.g. electrodes 32 of silver, copper, nickel, gold or aluminium, on a quartz wafer or a layer of silicon oxide or glass, on the wafer; by thinning the piezo-electric wafer between the regions " a "; or by making the device of piezo-electric material e.g. quartz, in the regions " a " and of some other material e.g. aluminium or fused quartz in the surrounding regions " b." In examples, the regions " a " and " b " can be formed from monocrystalline or ceramic materials of different densities bonded together by glass, or from glass pellets selectively diffused into the surface of a ceramic wafer. The piezoelectric material may be quartz, Rochelle salt, dipotassium tartrate, lithium sulphate, or AT- cut quartz, or polarizable ferroelectric ceramic material, e.g. barium titanate or lead zinconatelead titanate, operated in a thickness shear, thickness twist or torsional mode.