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Enhancing the Dielectric Property of 0.69PZT-0.31PZNN Thick Films by Optimizing the Poling Condition
송다니엘,우민식,안정환,성태현 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.10
We investigated how the applied electric-field’s magnitude and the poling time affected, respectively, the dielectric property and the microstructure of piezoelectric lead zirconate titanate/lead zirconate nickel niobate (PZT-PZNN) thick films in order to apply the films to piezoelectric energy harvesters. Several 300-μm-thick, 10 × 10-mm2 PZT-PZNN squares were tape cast, laminated, sintered, and poled under 2-, 4-, 6-, 10-, 14-, and 15-kV/mm electric fields for 30 min. The 10-kV/mm electric field produced the highest d33 × g33 without mechanically damaging the sample. Further, samples were sintered at 950, 1000, and 1020 C and subsequently poled at 10 kV/mm (previously determined as the magnitude of the optimal poling electric field) for 15, 30, 60, 120, and 240 min to investigate how the poling time affected the piezoelectric ceramic’s microstructure. The optimal poling time for all the sintered samples was 60 min. Further, the piezoelectric ceramics composed of small grains and poled longer than 60 min showed higher dielectric constants. However, those composed of large grains and poled for times shorter than 60 min showed higher dielectric constants because the element mobility of the piezoelectric ceramics increased with increasing poling time.
송다니엘,우민식,안정환,성태현,김경범 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.12
We investigated how the viscosities of piezoelectric lead zirconate titanate/lead zirconate nickelniobate (PZT-PZNN) slurry samples affect the laminated-film densities based on various conditionsof degassing time for 0, 30, and 60 min. PZT-PZNN slurries with different viscosities were tapecasted into green sheets by adjusting the comma blade height to 100, 200, 300, 400, and 500μm. As a result the slurry viscosity linearly increased with increasing slurry degassing time, andthe thickness of the green sheet increased with increasing comma blade height. The density andthe dielectric properties of piezoelectric ceramic films with the same thicknesses, but composed ofdifferent numbers of layers, were compared. The laminated-film density and the dielectric propertyd33 × g33 increased with decreasing number of laminated layers. However, when the viscosity of theslurry was too high (degassing time > 60 min) and the comma blade height was too high (commablade height > 300 μm), the tape-casted green sheet was too thick to have enough time to dry. Bycontrolling the slurry viscosity by adjusting the degassing time and the comma blade height, wewere able to optimize the thickness of the green sheet in a tape-casting. The optimal green sheetthickness was < 70 μm, and the number of sheets laminated should be minimized to increase thefilm’s density and dielectric constant.
안정환,우민식,송다니엘,Seong Kwang,Ki Hwan Baek,황성주,성태현 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.11
Two models were developed a pre-stress model and a no-pre-stress model for considering the effectsof a tip mass with and without pre-stress induced by gravity, respectively. Three tip masses−6,18, and 30 g−were used in experiments, and four cases were considered: the above three tip massesand a 0 g case, corresponding to no tip mass. Two prominent effects of the tip mass were theoreticallypredicted and experimentally verified. We established an evaluation standard and ananalysis technique for efficiently analyzing these two effects of the tip mass on the output power ofa piezoelectric energy-harvesting system. For both models, a higher output power was obtained ina system with a tip mass than in a system without a tip mass. Results of the experiments and of acritical voltage analysis demonstrated that the developed tip mass method successfully augmentedthe output power of the system.
Designing and manufacturing a piezoelectric tile for harvesting energy from footsteps
황성주,정현준,김정훈,안정환,송다니엘,송예원,이희락,문성필,박현수,성태현 한국물리학회 2015 Current Applied Physics Vol.15 No.6
The objective of this research is to design a piezoelectric tile for harvesting energy from footsteps and to optimize the system for harvesting maximum energy. Because piezoelectric modules easily break when directly subjected to energy generated by human movements, we designed a tile that employs indirect energy transmission using springs and a tip mass. We aimed at matching the mechanical resonance frequency of the tile with that of the piezoelectric modules. The resonance frequency of a piezoelectric module with a 10-g tip mass was almost similar to the vibration frequency of the tile at 22.5 Hz when we dropped an 80-g steel ball from a 1-m height. We performed impedance matching and realized a matching value of 15 kU. Under these optimal mechanical and electrical conditions, we harvested 770- ΩW RMS and 55-μW peak output power.