A thickness-mode piezoelectric micromachined ultrasound transducer annular array using a PMN–PZT single crystal

Micro-electromechanical system (MEMS) technologies were used to develop a thickness-mode piezoelectric micromachined ultrasonic transducer (Tm-pMUT) annular array utilizing a lead magnesium niobate–lead zirconate titanate (PMN–PZT) single crystal prepared by the solid-state single-crystal-growth method. Dicing is a conventional processing method for PMN–PZT single crystals, but MEMS technology can be adopted for the development of Tm-pMUT annular arrays and has various advantages, including fabrication reliability, repeatability, and a curved element shape. An inductively coupled plasma–reactive ion etching process was used to etch a brittle PMN–PZT single crystal selectively. Using this process, eight ring-shaped elements were realized in an area of 1  ×  1 cm2. The resonance frequency and effective electromechanical coupling coefficient of the Tm-pMUT annular array were 2.66 (±0.04) MHz, 3.18 (±0.03) MHz, and 30.05%, respectively, in the air. The maximum positive acoustic pressure in water, measured at a distance of 7.27 mm, was 40 kPa from the Tm-pMUT annular array driven by a 10 Vpp sine wave at 2.66 MHz without beamforming. The proposed Tm-pMUT annular array using a PMN–PZT single crystal has the potential for various applications, such as a fingerprint sensor, and for ultrasonic cell stimulation and low-intensity tissue stimulation.

Source:IOPscience

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High infrared transmittance CdS single crystal grown by physical vapor transport

Φ55 × 15 mm2 CdS bulk single crystal with high infrared transmittance was grown by physical vapor transport. The single crystal has a consistent structure from top to bottom, which was confirmed by X-ray diffraction. The (002) full-width at half-maximum of the X-ray diffraction was measured to be 60.00 arcsec, indicating a good quality of the structure. Hall mobility, specific resistivity, and carrier concentration for the top and bottom of the crystal were observed as well. Transmittance for the CdS single crystal was measured to be higher than 70% from 2.5 to 4.5 µm, making the single crystal an important candidate for infrared window materials. Furthermore, the absorption mechanism of the CdS single crystal was analyzed.

Source:IOPscience

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Growth, structural and mechanical studies of phthalic acid single crystals grown in two different solutions

Good quality pure Phthalic acid single crystals were grown by slow evaporation solution growth method. Phthalic acid 1(PA1) crystals were grown in Ammonium Oxalate aqueous solution. From the aqueous solution of Ammonium Bromide, Phthalic acid 2 (PA2) crystals were grown. Single crystal x-ray diffraction and Mechanical characterizations of slow evaporation grown single crystals of PA1 and PA2 were analyzed in this article. Lattice parameters, space group and crytal system were found from Single crystal x-ray diffraction analysis. Optical tranmittance study reaveal the optical perfection of the crystals. Mechanical properties such as Vicker's microhardness number, work hardening index, standard hardness values, Yield strength, fracture toughness, brittleness index and elastic Stiffness constant values were determined using Vicker's microhardness tester.

Source:IOPscience

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