Abstract: A surface acoustic wave device having a lithium tatraborate single crystal substrate is proposed. An electro-mechanical coupling coefficient K.sup.2 of the substrate is about 1% so as to obtain a surface acoustic wave having sufficient practical energy. When cut angles of the substrate and a propagation direction of the surface acoustic wave are expressed by Eulerian angles (90+.lambda., 90.degree., 90.degree.), a thickness t of an electrode formed on the substrate falls within a region bounded by a dotted curve and an alternate long and short dash curve in FIG. 8. The dotted curve and the alternate long and short dash curve indicate the experimental relationship between the cut angle .lambda. and the thickness t when the TCD is set at 5 and -5 ppm/.degree.C., respectively. When the film thickness t is set within the above-mentioned range, the absolute value of the TCD is set at 5 ppm/.degree.C. or less. When the cut angle .lambda. is 25.degree., the TCD of the substrate becomes zero.

Abstract: A device for detecting infrared rays using the pyroelectric effect, namely a pyroelectric detector, and methods for manufacturing the pyroelectric detector, are disclosed. The pyroelectric detector comprises a pyroelectric material, an electrode for receiving infrared rays placed on one face of the pyroelectric material, a shield electrode placed at the other face of the pyroelectric material, a substrate made of a semiconductor or conductive material which is fastened to the shield electrode, the substrate having a hole corresponding in position to the position of the infrared receiving electrode and a stand to which the substrate is fastened.