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Natthaphon Bunnak,Pitak Laoratanakul,Amar S. Bhalla,Hathaikarn Manuspiya 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.3
Significant improvements in dielectric properties of poly(vinylidene difluoride) (PVDF) can be achieved by adding small amounts of barium-modified porous clay heterostructure (Ba-PCH). In this article, composite films of PVDF with various amounts of Ba-PCH were fabricated by the compression method. SEM images indicated good dispersion of Ba-PCH in the PVDF matrix, as island-like particles caused improvement in the mechanical and thermal properties in the composite films. The films were highly heat resistant between 446°C and 452°C, depending on the amount of Ba-PCH added. The addition of Ba-PCH in the PVDF matrix reduced the non-polar phase, α-phase, of the PVDF, which resulted in the presence of a polar-phase, β-phase. There was a decrement of the non-polar phase of PVDF after adding small amounts of Ba-PCH,the dielectric constant (at 1 kHz) was dramatically increased from 6.0 of the neat compressed PVDF film to 34.1, 44.8, 47.1, and 56.0 of the compressed PVDF film with 3 wt. %, 5 wt. %, 7 wt. %, and 10 wt. %of Ba-PCH in the PVDF matrix, respectively.
Jong Kuk Kim,Sang su Kim,Amar S. Bhalla,Eun Jin Choi,Tae Kwon Song,Won Jeong Kim 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.III
Undoped and Mn-doped BiFeO3 (BFO) thin films were deposited on Pt(200)/TiO2/SiO2/Si(100) substrates by a chemical solution deposition method. The coated films were annealed in the temperature range of 450 550 C for 30 min under nitrogen atmosphere. It was found that Mn-doped BFO thin films exhibited good ferroelectric properties, such as improved leakage current density and P-E hysteresis characteristics. The leakage current density of 3.5 × 10.6 A/cm2 for the 1.5-mol% Mn-doped BFO thin film annealed at 525 C is about four orders of magnitude lower than that of undoped BFO thin film at an external electric field of 100 kV/cm. They exhibited a well-saturated hysteresis loop with a remanent polarization (Pr) of 36 μC/cm2 at room temperature. The reason for the improved leakage current and ferroelectric properties in Mn-doped BFO thin films can be attributed to the Mn doping, that may be responsible for a reduction in oxygen vacancies.
Dielectric and impedance measurements on (1-x)Ba(Fe1/2Ta1/2) O3-xBa(Zn1/3Ta2/3)O3 ceramics
Thanatep Phatungthane,Gobwute Rujijanagul,Kamonpan Pengpat,Sukum Eitssayeam,Tawee Tunkasiri,Luiz F. Cotica,Ruyan Guo,Amar S. Bhalla 한국물리학회 2014 Current Applied Physics Vol.14 No.12
In this work, ((1x)Ba(Fe1/2Ta1/2)O3-xBa(Zn1/3Ta2/3)O3), ((1x)BFT-xBZT) ceramics with x ¼ 0.00e0.12 were synthesized by the solidestate reaction method. X-ray diffraction data revealed that both the powders and ceramics were of a pure-phase cubic perovskite structure. All ceramics showed large dielectric constants. For the x ¼ 0.12 sample, a very high dielectric constant (>20,600) was observed. A lowering in the dielectric loss compared to pure BFT ceramics was observed with the BZT addition. The impedance measurements indicated that BZT has a strong effect on the bulk grain and grain boundary resistance of BFT ceramics. These results are in agreement with the measured dielectric properties. Based on dielectric and impedance results, (1x)BFT-xBZT ceramics could be of great interest for high performance dielectric materials applications due their giant dielectric constant behavior.
Ivair A. Santos,Jaciele M. Rosso,Luiz F. Cotica,Taiana G.M. Bonadio,Valdirlei F. Freitas,Ruyan Guo,Amar S. Bhalla 한국물리학회 2016 Current Applied Physics Vol.16 No.11
In this contribution, a promising environmentally friendly lead-free ferroelectric/polymer 0-3 composite, using polyvinylidene fluoride and barium sodium titanate niobate compounds, was synthesized and structurally and dielectrically characterized. The results suggest the complete formation of a 0-3 connected composite with enhanced dielectric properties, reaching a relative permittivity of 32 and a dissipation loss of 4%, at 1 kHz and 300 K, respectively. These dielectric features are associated with the intimate contact between the polymer and ceramic fraction in the composite that lead to the increase of the polar b-phase amount in the polymer fraction, at room temperature.
Taiana G.M. Bonadio,Valdirlei F. Freitas,T^ania T. Tominaga,Ricardo Y. Miyahara,Jaciele M. Rosso,Luiz F. C otica,Mauro L. Baesso,Wilson R. Weinandb,,Ivair A. Santos,Ruyan Guo,Amar S. Bhalla 한국물리학회 2017 Current Applied Physics Vol.17 No.5
Bioactive ferroelectric composites based on polyvinylidene fluoride, hydroxyapatite and b-tricalcium phosphate have been synthesized and their structural, microstructural, bioactive, and ferroelectric properties are characterized. Structural and FTIR investigations showed the presence of the polar polyvinylidene fluoride (b2) phase, while ferroelectric characterizations revealed remnant polarizations and coercive field, around 0.04 mC/cm2 and 28 kV/cm, respectively, for these biocompatible samples. Structural and microstructural analysis of samples previously immersed in simulated body fluid for 7 days revealed a large apatite phase growth (1.45 mm) on the composites' surfaces as a strong indication of their elevated bioactivity and potentialities for bone tissue engineering.