High Acoustic Velocity Research Articles

High Velocity and High Coupling Surface Acoustic Waves Using ZnO Films on Ceramic Substrates with High Acoustic Velocity

The layered structure comprising a c-axis normally oriented ZnO piezoelectric film and Al2O3, AlN and SiC ceramic substrates which have high surface acoustic wave velocity and small surface roughness has given both high phase velocity and high coupling k2 for the 0th (Rayleigh) mode, 1st (Sezawa) mode, and leaky mode surface acoustic waves.

Microwave Surface Acoustic Wave Materials

Abstract : The acoustic wave properties of several piezoelectric crystals and a layered structure have been theoretically and experimentally investigated for possible application in microwave acoustic devices. A search was made for crystals and layered structures having one or more of the following properties: (i) temperature compensation, (ii) high piezoelectric coupling, (iii) low power flow angle, (iv) low loss and (v) low or high acoustic wave velocities. The acoustic waves studied were the bulk acoustic waves (BAW), the surface acoustic waves (SAW), the pseudo SAW (PSAW), the plate modes and the surface skimming bulk waves (SSBW). The wave properties studied were the velocity, piezoelectric coupling, the temperature coefficient of delay, diffraction and attenuation. The layered geometries examined studied included fused silica on LiNbO3 and gold, aluminum and copper layers on quartz. The overlay structures were found to be more temperature stable than the single crystals. A theory describing the spectrum of acoustic waves emanating from an interdigital transducer was developed. Several promising cuts for SSBW in quartz were identified and studied both theoretically and experimentally. Finally, various prototype SSBW devices were fabricated and tested.

Crustal Study of Transcontinental Strip East of Rocky Mountains: ABSTRACT

A set of aeromagnetic profiles for a strip 100 mi. wide extending from the Rocky Mountains to the edge of the continental shelf off the eastern coast of the United States reveals large anomalies of major crustal significance. The data consist of 20 profiles flown at a barometric altitude of approximately 5,000 feet, centered along a line from Denver, Colorado, to Washington, D.C., and spaced approximately 5 mi. apart. Several distinct anomalous patterns reflecting basement lithology can be clearly recognized. These include the Piedmont province in the eastern United States and the basalt flows in Iowa and Nebraska (mid-continent gravity high). The most intense anomalies occur in central and western Nebraska. Two anomalous areas in eastern Iowa and western Ohio probably are related to a single tectonic province and are correlatable with a pronounced horseshoe-shape gravity feature extending from eastern Iowa through eastern Minnesota across northern Lake Michigan and through the central part of Michigan and western Ohio. A linear magnetic anomaly at least 100 mi. long and 35 mi. wide is present over the Appalachian plateau and parallels the Appalachian structural trends. The large amplitude and areal extent of the magnetic anomalies and their obvious correlation with known gravity anomalies suggest intrabasement units of correspondingly high acoustic velocities. It is clear that these vertical lithologic discontinuities must be taken into account in deep refraction studies of the crust and upper mantle; otherwise, seismic interpretations based on horizontal discontinuities alone yield incorrect crustal thicknesses. End_of_Article - Last_Page 1092------------