In this work, a series of BaTiO3-based ceramic materials, Ba(Al0.5Nb0.5)xTi1-xO3 (x = 0, 0.04, 0.06, 0.08), were synthesized using a standard solid-state reaction technique. X-ray diffraction profiles indicated that the Al+Nb co-doping into BaTiO3 does not change the crystal structure significantly with a doping concentration up to 8 %. The doping ions exist in Al3+ and Nb5+ chemical states, as revealed by X-ray photoelectron spectroscopy. The frequencydependent complex dielectric properties and electric modulus were studied in the temperature range of 100~380 K. A colossal dielectric permittivity (>1.5 × 104) and low dielectric loss (<0.01) were demonstrated at the optimal dopant concentration x = 0.04. The observed dielectric behavior of Ba(Al0.5Nb0.5)xTi1-xO3 ceramics can be attributed to the Universal Dielectric Response. The complex electric modulus spectra indicated the grains exhibited a significant decrease in capacitance and permittivity with increasing co-doping concentration. Our results provide insight into the roles of donor and acceptor co-doping on the properties of BaTiO3-based ceramics, which is important for dielectric and energy storage applications.

New piezoelectric and triboelectric materials for energy harvesting are being widely researched to reduce their processing cost and complexity and to improve their energy conversion efficiency. In this study, BaTiO3 films of various thickness were deposited on Ni foams by R.F. magnetron sputtering to study the piezoelectric and triboelectric properties of the porous spongy structure materials. Then piezoelectric nanogenerators (PENGs) were prepared with spongy structured BaTiO3 and PDMS composite. The output performance exhibited a positive dependence on the thickness of the BaTiO3 film, pushing load, and poling. The PENG output voltage and current were 4.4 V and 0.453 μA at an applied stress of 120 N when poled with a 300 kV/cm electric field. The electrical properties of the fabricated PENG were stable even after 5,000 cycles of durability testing. The triboelectric nanogenerators (TENGs) were fabricated using spongy structured BaTiO3 and various polymer films as dielectrics and operated in a vertical contact separation mode. The maximum peak to peak voltage and current of the composite film-based triboelectric nanogenerator were 63.2 V and 6 μA, respectively. This study offers new insights into the design and fabrication of high output nanogenerators using spongy structured materials.

Piezoelectric technology, which converts mechanical energy into electrical energy, has recently attracted drawn considerable attention in the industry. Among the many kinds of piezoelectric materials, BaTiO3 nanotube arrays, which have outstanding uniformity and anisotropic orientation compared to nanowire-based arrays, can be fabricated using a simple synthesis process. In this study, we developed a flexible piezoelectric energy harvester (f-PEH) based on a composite film with PVDF-coated BaTiO3 nanotube arrays through sequential anodization and hydrothermal synthesis processes. The f-PEH fabricated using the piezoelectric composite film exhibited excellent piezoelectric performance and high flexibility compared to the previously reported BaTiO3 nanotube array-based energy harvester. These results demonstrate the possibility for widely application with high performance by our advanced f-PEH technique based on BaTiO3 nanotube arrays.

BaTiO3-Poly vinylidene fluoride (PVDF) solution was prepared by adding 0~25 wt% BaTiO3 nanopowder and 10 wt% PVDF powder in solvent. BaTiO3-PVDF film was fabricated by spreading the solution on a glass with a doctor blade. The output performance increased with increasing BaTiO3 concentration. When the BaTiO3 concentration was 20 wt%, the output voltage and current were 4.98 V and 1.03 μA at an applied force of 100 N. However, they decreased when the over 20 wt% BaTiO3 powder was added, due to the aggregation of particles. To enhance the output performance, the generator was poled with an electric field of 150~250 kV/cm at 100 °C for 12 h. The output performance increased with increasing electric field. The output voltage and current were 7.87 V and 2.5 μA when poled with a 200 kV/cm electric field. This result seems likely to be caused by the c-axis alignment of the BaTiO3 after poling treatment. XRD patterns of the poled BaTiO3-PVDF films showed that the intensity of the (002) peak increased under high electric field. However, when the generator was poled with 250 kV/cm, the output performance of the generator degraded due to breakdown of the BaTiO3-PVDF film. When the generator was matched with 800 Ω resistance, the power density of the generator reached 1.74 mW/m2. The generator was able to charge a 10 μF capacitor up to 1.11 V and turn on 10 red LEDs.

Single-atom Pd clusters anchored on t-BaTiO3 material was synthesized using hydrothermal and ultrasonic methods for the effective piezoelectric catalytic degradation of pollutants using vibration energy. XRD patterns of BaTiO3 loaded with monoatomic Pd were obtained before and after calcining, and showed typical cubic-phase BTO. TEM and HAADF-STEM images indicated single-atom Pd clusters were successfully introduced into the BaTiO3. The piezoelectric current density of the prepared Pd-BaTiO3 binary composite was significantly higher than that of the pristine BaTiO3. Under mechanical vibration, the nanomaterial exhibited a tetracycline decomposition rate of ~95 % within 7 h, which is much higher than the degradation rate of 56.7 % observed with pure BaTiO3. Many of the piezo-induced electrons escaped to the Pd-doped BaTiO3 interface because of Pd’s excellent conductivity. Single-atom Pd clusters help promote the separation of the piezo-induced electrons, thereby achieving synergistic catalysis. This work demonstrates the feasibility of combining ultrasonic technology with the piezoelectric effect and provides a promising strategy for the development of ultrasonic and piezoelectric materials.

One-dimensional (1D) piezoelectric nanostructures are attractive candidates for energy generation because of their excellent piezoelectric properties attributed to their high aspect ratios and large surface areas. Vertically grown BaTiO3 nanotube (NT) arrays on conducting substrates are intensively studied because they can be easily synthesized with excellent uniformity and anisotropic orientation. In this study, we demonstrate the synthesis of 1D BaTiO3 NT arrays on a conductive Ti substrate by electrochemical anodization and sequential hydrothermal reactions. Subsequently, we explore the effect of hydrothermal reaction conditions on the piezoelectric energy conversion efficiency of the BaTiO3 NT arrays. Vertically aligned TiO2 NT arrays, which act as the initial template, are converted into BaTiO3 NT arrays using hydrothermal reaction with various concentrations of the Ba source and reaction times. To validate the electrical output performance of the BaTiO3 NT arrays, we measure the electricity generated from each NT array packaged with a conductive metal foil and epoxy under mechanical pushings. The generated output voltage signals from the BaTiO3 NT arrays increase with increasing concentration of the Ba source and reaction time. These results provide a new strategy for fabricating advanced 1D piezoelectric nanostructures by demonstrating the correlation between hydrothermal reaction conditions and piezoelectric output performance.

Single crystals, which have complexed composition, are fabricated by solid state grain growth. However, it is hard to achieve stable properties in a single crystal due to trapped pores. Aerosol deposition (AD) is suitable for fabrication of single crystals with stable properties because this process can make a high density coating layer. Because of their unique features (nano sized grains, stress inner site), it is hard to fabricate single crystals, and so studies of grain growth behavior of AD film are essential. In this study, a BaTiO3 coating layer with ~ 9 μm thickness is fabricated using an aerosol deposition method on (100) and (110) cut SrTiO3 single crystal substrates, which are adopted as seeds for grain growth. Each specimen is heat-treated at various conditions (900, 1,100, and 1,300℃ for 5 h). BaTiO3 layer shows different growth behavior and X-ray diffraction depending on cutting direction of SrTiO3 seed. Rectangular pillars at SrTiO3 (100) and laminating thin plates at SrTiO3 (110), respectively, are observed.

목적 : 소다-라임-실리카 유리(soda-lime-silica glass,SG) 기판위에 Ti, Ba-naphthenates를 출발원료로 사용하고 졸겔법으로 나노 결정질 TiO2, BaTiO3 박막을 제조하였다. 박막의 특성을 분석하기 위하여 X-선 회절 분석, 전자현미경, UV스펙트럼을 이용하여 연구하였다. 방법 : 코팅용액을 soda-lime-silica glass 기판 위에 스핀코팅하고 공기분위기에서 500℃에서 열분해시켜 박막을 제조하였다. 제조된 TiO2, BaTiO3 박막의 결정화도는 고분해능 X-선 회절분석법으로 그리고 표면미세구조와 거칠기는 전계 방출 현미경과 원자간력 현미경으로 또 자외선(200〜380 nm), 가시광선(380〜750 nm), 적외선(750〜900 nm) 영역의 투과율은 UV-Visible-NIR 분광광도계로 측정되었다. 결과 : TiO2박막은 아나타제 상이 존재하였으며, BaTiO3 박막은 최고 피크가 확인되지 않았다. 열처리한 TiO2, BaTiO3 박막의 가시광선 투과율은 80% 이상의 투과율을 나타냈으며, BaTiO3 박막은 TiO2 박막보다 자외선 및 청광 차단율이 높았다. 결론 : BaTiO3 박막은 TiO2 보다 자외선 및 청광에 대해 더 높은 차단율이 나타냈으며, 가시광선 투과율은 제조된 모든 박막에서 80% 이상의 투과율이 측정되었다.

Piezoelectric energy harvesting technology is attracting attention, as it can be used to convert more accessible mechanical energy resources to periodic electricity. Recent developments in the field of piezoelectric energy harvesters (PEHs) are associated with nanocomposites made from inorganic piezoelectric nanomaterials and organic elastomers. Here, we used the BaTiO3 nanoparticles and piezoelectric poly(vinylidene fluoride) (PVDF) polymeric matrix to fabricate the nanocomposites-based PEH to improve the output performance of PEHs. The piezoelectric nanocomposite is produced by dispersing the inorganic piezo-ceramic nanoparticles inside an organic piezo-polymer and subsequently spin-coat it onto a metal plate. The fabricated organic-inorganic piezoelectric nanocomposite-based PEH harvested the output voltage of ~1.5 V and current signals of ~90 nA under repeated mechanical pushings: these values are compared to those of energy devices made from non-piezoelectric polydimethylsiloxane (PDMS) elastomers and supported by a multiphysics simulation software.

Lead free (1-x)(0.675BiFeO3-0.325BaTiO3)- xLiTaO3 (BFBTLT, x = 0, 0.01, 0.02, and 0.03, with 0.6 mol% MnO2 and 0.4 mol% CuO) were prepared by a solid state reaction method, followed by air quenching and their crystalline phase, morphology, dielectric, ferroelectric and piezoelectric properties were explored. An X-ray diffraction study indicates that lithium (Li) and tantalum (Ta) were fully incorporated in the BFBT materials with the absence of any secondary phases. Dense ceramic samples (> 92 %) with a wide range of grain sizes from 3.70 μm to 1.82 μm were obtained in the selected compositions (0 ≤ x ≤ 0.03) of BFBTLT system. The maximum temperatures (Tmax) were mostly higher than 420 oC in the studied composition range. The maximum values of maximum polarization (Pmax ≈ 31.01 μC/cm2), remnant polarization (Prem ≈ 22.82 μC/cm2) and static piezoelectric constant (d33 ≈ 145 pC/N) were obtained at BFBT-0.01LT composition with 0.6 mol% MnO2 and 0.4 mol% CuO. This study demonstrates that the high Tmax and d33 for BFBTLT ceramics are favorable for industrial applications.

Grain-growth behavior in the 95Na1/2Bi1/2TiO3-5BaTiO3 (mole fraction, NBT-5BT) system has been investigated with the addition of Na2CO3. When Na2CO3 is added to NBT-5BT, the growth rate is higher than desired and grains are already impinging each other during the initial stage of sintering. The grain size decreases as the sintering temperature increases. With the addition of Na2CO3, a liquid phase infiltrates the interfaces between grains during sintering. The interface structure can be changed to be more faceted and the interface migration rate can increase due to fast material transport through the liquid phase. As the sintering temperature increases, the impingement of abnormal grains increases because the number of abnormal grains increases. Therefore, the average grain size of abnormal grains can be decreased as the temperature increases. The phenomenon can provide evidence that grain coarsening in NBT-5BT with addition of Na2CO3 is governed by the growth of facet planes, which would occur via mixed control.

The structural formation of inorganic nanoparticles dispersed in polymer matrices is a key technology for producing advanced nanocomposites with a unique combination of optical, electrical, and mechanical properties. Barium titanate (BaTiO3) nanoparticles are attractive for increasing the refractive index and dielectric constant of polymer nanocomposites. Current synthesis processes for BaTiO3 nanoparticles require expensive precursors or organic solvents, complicated steps, and long reaction times. In this study, we demonstrate a simple and continuous approach for synthesizing BaTiO3 nanoparticles based on a salt-assisted ultrasonic spray pyrolysis method. This process allows the synthesis of BaTiO3 nanoparticles with diameters of 20-50 nm and a highly crystalline tetragonal structure. The optical properties and photocatalytic activities of the nanoparticles show that they are suitable for use as fillers in various nanocomposites.

The effects of an excess of Bi on the piezoelectric and dielectric properties of 0.60Bi1+xFeO3-0.40BaTiO3 (x = 0, 0.01, 0.03, 0.05, 0.07) were investigated. The ceramics were processed through a conventional solid state reaction method and then quenched after sintering at different temperatures in the range of 980~1070 oC. A single perovskite structure without any secondary phase was confirmed for all compositions and temperatures. It was found that excess Bi reduced the sintering temperatures, acted as a sintering aid and enhanced the properties in combination with quenching. Curie temperature (TC) was found to slightly increase due to the presence of excess Bi; electrical properties were also improved by quenching. At x = 0.03 and 1030 oC, remnant polarization (2Pr) was as high as 45.4 μC/cm2 and strain at 40 kV/cm was up to 0.176 %.

BaTiO3-coated Fe nanofibers are synthesized via a three-step process. α-Fe2O3 nanofibers with an average diameter of approximately 200 nm are first prepared using an electrospinning process followed by a calcination step. The BaTiO3 coating layer on the nanofiber is formed by a sol-gel process, and a thermal reduction process is then applied to the core-shell nanofiber to selectively reduce the α-Fe2O3 to Fe. The thickness of the BaTiO3 shell is controlled by varying the reaction time. To evaluate the electromagnetic (EM) wave-absorbing abilities of the BaTiO3@Fe nanofiber, epoxy-based composites containing the nanofibers are fabricated. The composites show excellent EM wave absorption properties where the power loss increases to the high frequency region without any degradation. Our results demonstrate that the BaTiO3@Fe nanofibers obtained in this work are attractive candidates for electromagnetic wave absorption applications.

Bi0.5Na0.5TiO3 (BNT) based ceramics are considered potential lead-free alternatives for Pb(Zr,Ti)O3(PZT) based ceramics in various applications such as sensors, actuators and transducers. However, BNT-based ceramics have lower electromechanical performance as compared with PZT based ceramics. Therefore, in this work, lead-free bulk 0.99[(Bi0.5Na0.5)0.935Ba0.065](1-x)LaxTiO3-0.01SrZO3 (BNBTLax-SZ, with x = 0, 0.01, 0.02) ceramics were synthesized by a conventional solid state reaction The crystal structure, dielectric response, degree of diffuseness and electric-field-induced strain properties were investigated as a function of different La concentrations. All samples were crystallized into a single phase perovskite structure. The temperature dependent dielectric response of La-modified BNBT-SZ ceramics showed lower dielectric response and improved field-induced strain response. The field induced strain increased from 0.17% for pure BNBT-SZ to 0.38 % for 1 mol.% La-modified BNBT-SZ ceramics at an applied electric field of 6 kV/mm. These results show that Lamodified BNBT-SZ ceramic system is expected to be a new candidate material for lead-free electronic devices.

분산된 유전입자를 가지는 OLED는 입자의 표면 상태에 의하여 새로운 부가적인 결과를 나타내게 된다. 본 논문에서는 유전입자가 분산된 Polyfluorene (PFO) 발광 층과 두 개의 전극을 가지는 간단한 구조의 PFO-base OLED를 제작하고 분산된 나노입자들이 분산을 위한 제작공정에서 필수적으로 발생하는 표면상태변화가 소자에 어떠한 영향을 미치는지 알아보았다. Spin-coating 공법으로 제작된 PFO-base OLED는 극소량 첨가된 유전입자의 고른 분산을 위한 공정이 필요하며 이 공정으로 인해 입자의 표면에서 scratch 가 증가 하고 , 또한 입자의 분쇄가 이루어 지기도 한다. 교반 시간의 증가는 표면 scratch와 입자의 분쇄를 증가시키게 되고, 이는 입자크기의 감소와 분쇄된 입 자끼리의 응집을 증가시켜 소자의 electrical conditioning을 변화시켰고 나아가 발광 특성에 영향을 주었다. 실험 결과 9시간 정도의 교반시간에서 입자의 표면전하로 인해 electrical conditioning이 개선되고 이로서 소자의 발광휘도가 최대 2.5배 이상 증가하였다. 반면에 교반시간이 증가하면 소자의 전반적인 휘도는 다소 감소하는 결과를 나타내었다. 이는 표면전하 증가와 함께 분산이 고르게 되지 않기 때문인 것으로 생각된다.

Polyfluorene (PFO) 발광 층과 두 개의 전극으로 이루어진 단순한 구조의 PFO polymer base OLED를 기본으로 강유전성의 BaTiO₃나노입자를 PFO 발광 층 내에 분산시킨 OLED 소자를 제작하여 분산된 강유전체 나노입자의 영향과 동작에 미치는 역할을 알아보았다. 140 nm 두께의 발광 층 내부에 대비 80 nm의 크기를 가지는 강유전성 BaTiO₃입자들은 OLED 동작 중에 인가전압에 의해 대전되어 전기쌍극자를 형성하고, PFO의 발광 층 내로 주입된 전자 및 정공들과 각각 coulomb force에 기인하는 상호작용을 하여 OLED 소자의 전류밀도가 증가하는 결과를 나타내었다. PFO의 질량대비 10 wt% 에 해당하는 소량을 첨가하였을 때에 OLED소자의 문턱전압이 약 2 V 감소하는 개선된 결과를 나타내었다. 또한 유전체가 첨가되지 않은 소자에 비하여 휘도가 약 2 배 증가한 결과를 나타내었다.

Flexible BaTiO3 films as dielectric materials for high energy density capacitors were deposited on polyethyleneterephthalate (PET) substrates by r.f. magnetron sputtering. The growth behavior, microstructure and electrical properties of theflexible BaTiO3 films were dependent on the sputtering pressure during sputtering. The RMS roughness and crystallite size ofthe BaTiO3 increased with increasing sputtering pressure. All BaTiO3 films had an amorphous structure, regardless of thesputtering pressures, due to the low PET substrate temperature. The composition of films showed an atomic ratio (Ba:Ti:O)of 0.9:1.1:3. The electrical properties of the BaTiO3 films were affected by the microstructure and roughness. The BaTiO3 filmsprepared at 100mTorr exhibited a dielectric constant of ~80 at 1kHz and a leakage current of 10−8A at 400kV/cm. Also, filmsshowed polarization of 8µC/cm2 at 100kV/cm and remnant polarization (Pr) of 2µC/cm2. This suggests that sputter depositedflexible BaTiO3 films are a promising dielectric that can be used in high energy density capacitors owing to their high dielectricconstant, low leakage current and stable preparation by sputtering.

In this study, BaTiO3 thin films were grown by RF-magnetron sputtering, and the effects of the thin film thickness on the structural characteristics of BaTiO3 thin films were systematically investigated. Instead of the oxide substrates generally used for the growth of BaTiO3 thin films, p-Si substrates which are widely used in the current semiconductor processing, were used in this study in order to pursue high efficiency in device integration processing. For the crystallization of the grown thin films, annealing was carried out in air, and the annealing temperature was varied from 700˚C. The changed thickness was within 200 nm~1200 nm. The XRD results showed that the best crystal quality was obtained for ample thicknesses 700 nm~1200 nm. The SEM analysis revealed that Si/BaTiO3 are good quality interface characteristics within 300 nm when observed thickness. And surface roughness observed of BaTiO3 thin films from AFM measurement are good quality surface characteristics within 300 nm. Depth-profiling analysis through GDS (glow discharge spectrometer) showed that the stoichiometric composition could be maintained. The results obtained in this study clearly revealed BaTiO3 thin films grown on a p-Si substrate such as thin film thickness. The optimum thickness was 300 nm, the thin film was found to have the characteristics of thin film with good electrical properties.

전도성 고분자 PFO(Polyfluorene)에 양전극 ITO와 음전극으로 AI 를 추가한 단순한 양극성 구조의 ITO/PFO/Al 소자를 제작하였다. PFO에 BaTIO₃나노세라믹스 분말을 중량비로 0wt%, 10wt%, 20wt% 와 30wt% 로 달리한 4종류의 시편에 만들고, Keithley 사의 2400 Sourcemeter를 이용하여 0V에서 21V까지 DC전압을 인가하면서 소자에 흐르는 전류량을 관찰하였다. 수 나노 크기의 BaTIO₃분말의 첨가는 PFO/AI 계면에서의 전위장벽을 감소시켜 Fowler-Nordheim Tunneling이 시작되는 전압이 BaTIO₃가 첨가되지 않은 시편의 경우에 비하여 7V에서 최대 10V가 낮아진 결과를 얻었다. 소자에 흐르는 최대 전류값은 인가 전압 DC21V일 때 BaTIO₃첨가량에 비례하여 4배에서 5.5배까지 증가하였다. BaTIO₃의 첨가효과는 20wt% 이상 첨가된 경우 효과가 포화되기 시작하여, 30wt%의 BaTIO₃를 첨가한 시편의 전류량은 오히려 감소하였고 전류주입도 어려워지는 상반된 결과를 얻었다. 이것은 첨가한 나노 분말의 표면전하가 만드는 미세전계의 영향이 인접한 거리에서 서로 중첩되어 전류의 흐름이 오히려 감소하는 결과를 보인 것을 판단된다. 이로서 강유전체가 첨가된 전도성 고분자/금속 계면의 I-V 특성은 나노 세라믹스 분말의 표면전하가 만드는 국소미세전계의 영향을 받아 Trap Charge Limited Current 모델에 부합하는 결과를 가짐을 알 수 있었다.