J.C. Field

Bio: J.C. Field is an academic researcher from University of Maine. The author has contributed to research in topics: Surface acoustic wave & Acoustic wave. The author has an hindex of 4, co-authored 5 publications receiving 57 citations.

Berlinite, a temperature‐compensated material for surface acoustic wave applications

Abstract: The surface and pseudosurface acoustic wave properties of berlinite (α‐AlPO4) have been theoretically predicted in order to evaluate the merit of using this material in related surface acoustic wave devices The surface and pseudosurface acoustic wave velocities, an estimate of the electromagnetic to acoustic coupling, the temperature coefficient of delay, the powerflow angle, and the attenuation have been determined for several standard crystallographic cuts These results supplement the results given by Carr and O’Connell This material is shown to possess several temperature‐compensated cuts and about four times the coupling of α‐quartz It is pointed out that α‐AlPO4 may be only one of many potentially temperature‐compensated materials with a silica derivative‐type structure

New Low Loss High Coupling Mode Up to 1 GHz on LiNbO 3

Abstract: : Experimental measurements of 345 MHz surface acoustic waves propagating along the X-axis of Z-cut lithium niobate have revealed the existence of a low-loss, high-coupling mode whose insertion loss is less than the Rayleigh-type surface acoustic wave. When the double electrode of quarter-wavelength transducers were excited at the third overtone at 1035 MHz, the insertion loss of this mode was about 10 dB less than that of the SAW. The experimentally observed velocity of this mode was 4375 m/sec, considerably higher than the metalized SAW velocity of 3800 m/sec, but in excellent agreement with the theoretical calculated metalized pseudo SAW velocity. The experimentally determined coupling (v/v) for this mode is almost a factor of three times that of the SAW. This volume mode is in low-loss, broadband signal processing devices. (Author)

Temperature compensated cuts with zero power flow in TI3VS4 and TI3TaSe4

Abstract: Crystallographic orientations have been identified in TI3VS4 and TI3TaSe4 which are temperature compensated and have zero power flow. The orientations appear in the (110) axis cylinder cut and possess rather low s.a.w. velocities and reasonably high coupling.

Berlinite, A Temperature Compensated Material for Surface Acoustic Wave Applications

Abstract: The surface and pseudosurface acoustic wave properties of berlinite (α-AlPO 4 ) have been theoretically predicted in order to evaluate the merit of using this material in related surface acoustic wave devices. The surface and pseudosurface acoustic wave velocities, an estimate of the electromagnetic to acoustic coupling, the temperature coefficient of delay, the powerflow angle, and the attenuation have been determined for several standard crystallographic cuts. These results supplement the results given by Carr and O'Connell. This material is shown to possess several temperature-compensated cuts and about four times the coupling of α-quartz. It is pointed out that α-AlPO 4 may be only one of many potentially temperature-compensated materials with a silica derivative-type structure.

Acoustic wave biosensors

Abstract: Acoustic waves excited in a piezoelectric medium provide an attractive technology for realizing a family of biosensors that are sensitive, portable, cheap and small. In this paper a wide range of bulk and surface-generated acoustic waves are described and prototype sensing-element geometries are presented. Results obtained using several candidate acoustic wave biosensors are also discussed.

An acoustic plate mode biosensor

Abstract: A prototype biosensor, which utilizes an acoustic plate mode (APM) in a piezoelectric crystal plate as the sensing element, has been designed, fabricated and tested. The APM is selectively excited and received by aluminum interdigital transducers (IDTs), which are fabricated on a Z-cut X-propagating lithium niobate (ZX-LiNbO3) substrate using standard photolithographic techniques. The biological film is bound to the face of the ZX-LiNbO3 plate opposite to the IDTs. Appropriate r.f. electronics are used with the APM device to form the complete biosensor. Tests relating to the detection of deoxyribonucleic acid (DNA) hybridization demonstrate that the biosensor exhibits a high level of sensitivity, selectivity and reproducibility.

On the use of ZX-LiNbO3 acoustic plate mode devices as detectors for dilute electrolytes

Abstract: Acoustic plate mode (APM) devices on Z-cut, X-propagating LiNbO3, a high piezoelectric coupling material, are investigated as detectors in dilute electrolyte or metal-ion solutions. The sensing wave is an APM, a slow shear wave coupled to the interdigital transducer, which results in a relatively strong acoustic-ionic interaction. The resulting electrical loading leads to a measurable perturbation in the wave-propagation characteristics, which can then be related to the liquid electrical properties. Experiments conducted at different frequencies with various solutions that compare well with theoretical results show a detector that is at least two orders of magnitude more sensitive than similar APM sensors on quartz. These promising results have also led to the investigation of the detection of aqueous transition-metal ions (Fe3+, Cu2+, etc.) using solution conductivity changes rather than the commonly used mass sensitivity. The method involves the bonding of metal ions in soluiton to a ligand-coated silica or LiNbO3 support, placed adjacent to the APM device and in the path of the liquid flow. The resulting frequency increase is then interpreted in terms of the concentration of the metal ions. X-ray photoelectron spectroscopy analysis of the coated surface is performed to confirm the binding.

A1P04-A12O3 catalysts with low alumina content

Abstract: A series of amorphous AlPO4-Al2O3 (APA1-A) catalysts were prepared to contain various A1PO4/Al2O3 weight ratios (Al2O3: 5–15 wt.%). The effect of the weight ratio and calcination temperature (at 773–1273 K, for 3 h) on the structure and texture of the resultant catalysts were determined. The samples were characterized by nitrogen adsorption-desorption, thermogravimetric analysis, differential thermal analysis. X-ray diffraction, high resolution 27Al and 31P MAS NMR and diffuse reflectance infrared Fourier transform spectroscopy. The presence of Al2O3 greatly affected the surface properties of AlPO4 upon heating, exerting a protective effect against sintering, and delaying the crystallization process. The thermal stability of the texture of the APAl-A systems was found to be considerably improved, in comparison with the AlPO4 catalyst, by the stabilization of the amorphous structure in the APA1-A systems, which was found to be fully retained, in the presence of Al2O3, upon calcination up to 1073 K. Calcination at 1273 K develops AlPO4 crystallinity in the α-cristobalite polymorph (which is greater as the Al2O3 content increases) but AlPO4 inhibits both the crystallization of the γ-Al2O3 phase and the γ- to α-Al2O3 phase transition. In particular, incorporation of 5 wt.-% Al2O3 resulted in an APAl-A system with remarkable thermal stability, after calcination, over the entire range of temperatures studied (773–1273 K). Amorphous APA1-A systems contain both tetrahedral and octahedral aluminum (their ratio varies with the Al2O3 content and the calcination temperature) while phosphorus always remains in P(OAl)4 environments. After calcination at 1273 K, only tetrahedral aluminum was found. Two types of aluminum surface hydroxyl groups (at 3786 and 3728 cm−1) and only one type of phosphorus surface hydroxyl group (at 3670 cm−1) are found in the DRIFT spectra. Furthermore, bands at 1130 and 478 cm−1 are found in the skeletal region. These are due to the triply degenerate P-O stretching vibration v3 mode of tetrahedral (PO4)3− and to the triply degenerate O-P-O bending variations v4 mode of (PO4)3− tetrahedra, respectively. A band at 714 cm−1, due to the stretching vibrations of Al-O bonds in combination with P-O bonds, is also found. Therefore the diffuse reflectance infrared Fourier transform spectra substantiated the structural changes in the samples in agreement with XRD and 27Al and 31P MAS NMR.