|Author:||Lee, Siu To Felix|
|Title:||Studies on (Ba₀.₉₅Sr₀.₀₅)(Zr₀.₀₅Ti₀.₉₅)O₃/polymer composites|
|Subject:||Barium compounds -- Electric properties.|
Ceramic materials -- Electric properties.
Composite materials -- Electric properties.
Hong Kong Polytechnic University -- Dissertations
|Department:||Department of Applied Physics|
|Pages:||xix, 121 leaves : ill. ; 30 cm.|
|Abstract:||The main objectives of the present work are to fabricate and study the properties of peroskite lead-free ceramic barium strontium zirconate titanate (abbreviated as BSZT) and its composites. BSZT with composition of Ba₀.₉₅Sr₀.₀₅Zr₀.₀₅Ti₀.₉₅O₃ is fabricated by a solid-state reaction method and studied in this project. The dielectric, piezoelectric and ferroelectric properties of this composition of BSZT have been measured. It is found that BSZT has piezoelectric constant of 270 pC/N, loss tangent tan δ of 1.5 % and thickness electromechanical coupling factor kt of 0.45. In this work, 2 different types of composites are fabricated, they include BSZT/polyvinylidene fluoridetrifluoroethylene [P(VDF-TrFE)] 0-3 composites and BSZT/epoxy 1-3 composites. High frequency ultrasonic transducers of 40 MHz have been fabricated using BSZT ceramics. Their bandwidth and two-way insertion loss are measured by the pulse-echo method. The bandwidth can reach up to 75 % with insertion loss of -26 dB. The transducers have been used for imaging and integrated into microfluidic channel to detect the acoustic velocity of the liquid under test. BSZT/P(VDF-TrFE) 0-3 composites with different ceramic volume fractions (Φ) ranging from 0.10 to 0.40 have been fabricated by dispersing fine BSZT powder evenly into the copolymer matrix. The pyroelectric coefficient and dielectric properties have been measured and compared with calculation using the Bruggeman's model. 0-3 composite with Φ = 0.30 has been found to have the best pyroelectric figure of merit. BSZT/epoxy 1-3 composites with ceramic volume fractions ranged from 0.55-0.85 have been fabricated by a dice-and-fill method. The resonance characteristics are measured and compared with the calculated results by the modified parallel and series model. Both measured and calculated results show that Φ = 0.65 has the best kt and it has been used to fabricate a low-frequency ultrasonic transducer.|
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