Improved Multilayered (Bi,Sc)O3-(Pb,Ti)O3 Piezoelectric Energy Harvesters Based on Impedance Matching Technique.

As a piezoelectric material, (Bi,Sc)O3-(Pb,Ti)O3 ceramics have been tested and analyzed for sensors and energy harvester applications owing to their relatively high Curie temperature and high piezoelectric coefficient. In this work, we prepared optimized (Bi,Sc)O3-(Pb,Ti)O3 piezoelectric materials through the conventional ceramic process. To increase the output energy, a multilayered structure was proposed and designed, and to obtain the maximum output energy, impedance matching techniques were considered and tested. By varying and measuring the energy harvesting system, we confirmed that the output energies were optimized by varying the load resistance. As the load resistance increased, the output voltage became saturated. Then, we calculated the optimized output power using the electric energy formula. Consequently, we identified the highest output energy of 5.93 µW/cm2 at 3 MΩ for the quadruple-layer harvester and load resistor using the impedance matching system. We characterized and improved the electrical properties of the piezoelectric energy harvesters by introducing impedance matching and performing the modeling of the energy harvesting component. Modeling was conducted for the piezoelectric generator component by introducing the mechanical force dependent voltage sources and load resistors and piezoelectric capacitor connected in parallel. Moreover, the generated output voltages were simulated by introducing an impedance matching technique. This work is designed to explain the modeling of piezoelectric energy harvesters. In this model, the relationship between applied mechanical force and output energy was discussed by employing experimental results and simulation.

AC Conductivity and Dielectric Properties of (1-x)(0.94Bi0.5Na0.5TiO3-0.06BaTiO3)-xTa Lead Free Ceramics.

Piezoelectric ceramics such as Pb(Zr,Ti)O3 (PZT) are currently used by electronic devices because of their superb properties. Lead-based ceramics has caused a lot of environmental problems due to their toxicity. So, lead-free ceramics have been studied as an alternative method due to the toxicity of lead-based ceramics. Lead-free energy harvesting application (Bi0.5N0.5)TiO3-BaTiO3 (BNT-BT), is famous for its excellent piezoelectric and electrical properties. The substitution of BNT-BT and Ta5+ also is very effective in improving the relative dielectric permittivity and electrical properties. Because of the device performance depends on the relative dielectric permittivity, temperature and frequency of ceramic are very important condition. In this study, the electrical and relative dielectric permittivity of substitution of BNT-BT with Ta will be analyzed and AC conductivity depending on temperature and frequency will be shown. Also, it will calculate and analyze activation energy in different ranges of frequency.

Energy Harvesting Through Wasted Thermal Energy by Light Grid Sources.

In this study, emitted light energy and the recycling of thermal energy from the arrays of a light emitting diode system were investigated. A light grid system is composed of the array of high power LED chips, thermoelement and heat sink. High power LED source has an advantage of high luminous efficiency, which combined with wasted thermal energy. Thermal energy loss can be regarded wasted energy. However, this wasting thermal energy can be effectively converted to the electrical energy from thermoelement and heat sink of a light grid system. By introducing the light grid system, the optical energy and thermal energy can be more effectively managed. In particular, we have intensively studied energy conversion efficiency of light grid system and energy harvesting characteristic through thermal energy.

Flexible Energy Harvester Based on Poly(vinylidene fluoride) Composite Films.

In these days, we are facing emerging energy crisis due to depletion of fossil fuels. Therefore, renewable energy which is based on wind energy, mechanical force energy, microwave energy and vibrations energy have attracted a lot of attentions. Piezoelectric energy harvesting is one of the promising renewable energy sources. As the use portable electronic devices increases, the need for portable renewable energy sources further increases. Especially, piezoelectric materials can be the best selection due to their robust properties. In this research, piezoelectric composites were prepared and investigated for piezoelectric energy harvesting applications. In this study, two types of flexible energy harvesters, 0.36BS-0.64PT-PVDF composite and PVDF film, were prepared and analyzed. Due to its high Curie temperature and low lead content, BS-PT is expected to be a substitute for PZT in the near future. The composite materials based on the PVDF and 0.36BS-0.64PT film showed higher open circuit voltage (0.73 V) than PVDF film (0.49 V). Also, the stored voltage of 0.36BS-0.64PT-PVDF composite film was 330 nJ which is 5.68 times higher than 58 nJ for PVDF films. By introducing the piezoelectric BS-PT ceramics, 0.36BS-0.64PT-PVDF composite film shows the enhanced performance such as open circuit voltage, energy and dielectric constant compared with those of PVDF materials. It seems that 0.36BS-0.64PT-PVDF composite film is more suitable for flexible energy device.

Spring-Based Active Shock Absorber Systems with Piezoelectric Energy Harvesters.

In this research, energy harvesters with different types of spring-based shock absorbers were invested for the active shock absorber applications. Two different types of spring-based shock absorbers were prepared for the comparison, coil type spring-based shock absorbers and specially designed slice type spring-based shock absorbers. Shock absorbers have been widely employed to protect the complicated main system by cancelling the applied mechanical forces from outsides. Therefore, in the classical points of view, shock absorber can be prepared by the elastic materials to store and release the applied mechanical energy with sequentially in the form of elastic energy, thermal energy, and sound energy. However, in recently, there are strong demands to replace this classical shock absorber to the energy harvesters, which can collect the wasted energy in the form of electrical energy. Therefore, in this research, alternative two different types of spring-based advanced shock absorber will be presented and discussed. To combine with the spring-based shock absorber, multilayered piezoelectric energy harvesters were attached to collect the applied mechanical energy.

Relaxation-Related Piezoelectric and Dielectric Behavior of Bi(Mg,Ti)O3⁻PbTiO3 Ceramic.

Piezoelectric and dielectric materials have attracted much attention for their functional device applications. Despite its excellent piezoelectric properties, the content of lead in piezoelectric materials should be restricted to prevent future environmental problems. Therefore, reduced lead content in piezoelectric materials with similar piezoelectric properties is favorable. In our research, piezoelectric materials with decreased lead content will be studied and discussed. Even though the lead content is decreased in Bi(Mg0.5Ti0.5)O3-PbTiO3 ceramics, they show piezoelectric properties similar to that of lead zirconate titanate (PZT)-based materials. We believe this high piezoelectric behavior is related to the relaxation behavior of Bi(Mg0.5Ti0.5)O3-PbTiO3 (BMT-PT) ceramics. In this study, 0.62Bi(Mg0.5Ti0.5)O3-0.38PbTiO3 ceramics were prepared by the conventional sintering process. These piezoelectric ceramics were sintered at varying temperatures of 975-1100 °C. Crystallinity and structural properties were analyzed and discussed. X-ray diffraction pattern analysis demonstrated that the optimal sintering temperature was around 1075 °C. A very high Curie temperature of 447 °C was recorded for 0.62BMT-0.38PT ceramics sintered at 1075 °C. For the first time, we found that the origin of the high Curie temperature, d33, and the dielectric constant is the relaxation behavior of different dipoles in 0.62BMT-0.38PT ceramics.

Pyroelectric and Piezoelectric Properties of (1-x)Na0.5K0.5NbO3-xBiScO3 Lead-Free Ceramics.

In this research, the pyroelectric and piezoelectric properties of (1 - x)Na0.5K0.5NbO3-xBiScO3 ceramics were investigated and analyzed. (Na, K)NbO3 based (1 - x)Na0.5K0.5NbO3-xBiScO3 ceramics were prepared by a conventional mixed oxide method. As the substituent, BiScO3 material enhanced the sintering mechanism of NKN ceramic, which improved the density, pyroelectric and piezoelectric properties, without any structural distortion. In this study, the structural dependent improved piezoelectric properties of (1 - x)Na0.5K0.5NbO3-xBiScO3 ceramics were investigated with various sintering temperatures. Also, the pyroelectric properties of (1 - x)Na0.5K0.5NbO3-xBiScO3 ceramics were observed up to 200 °C for the devices applications. The crystalline structures of the (1-x)Na0.5K0.5NbO3-x BiScO3 ceramics were measured by X-ray diffraction (XRD). The microstructure was examined by field emission scanning electron microscopy (FE-SEM). In addition, piezo-electric charge coefficient d33 and pyroelectric coefficient will be discussed.

Angle Dependent 3-D Directional Patterning of Flexible Films by Infrared Laser.

Laser direct patterning (LDP) technology has attracted great attention due to its process simplification and environmental friendliness. It is replacing the existing photo-lithography technology. Infrared (IR) laser equipment also has advantages such as low cost and long duration, although it is difficult to implement fine line width compared to ultraviolet (UV) or excimer laser. Therefore, it is very important to realize 3-D patterning system based on cheap infrared laser system. In this paper, 3-D infrared laser direct patterning system was designed by introducing an etching process on Ag paste/ITO/PET flexible film. Such 3-D patterned Ag paste/ITO/PET flexible films showed feasibility and effectiveness of 3-D laser directional patterning technologies. Etch ratio of the fabricated Ag paste/ITO/PET flexible film after 3-D infrared laser direct patterning was then systematically investigated.

Recycled Thermal Energy from High Power Light Emitting Diode Light Source.

In this research, the recycled electrical energy from wasted thermal energy in high power Light Emitting Diode (LED) system will be investigated. The luminous efficiency of lights has been improved in recent years by employing the high power LED system, therefore energy efficiency was improved compared with that of typical lighting sources. To increase energy efficiency of high power LED system further, wasted thermal energy should be re-considered. Therefore, wasted thermal energy was collected and re-used them as electrical energy. The increased electrical efficiency of high power LED devices was accomplished by considering the recycled heat energy, which is wasted thermal energy from the LED. In this work, increased electrical efficiency will be considered and investigated by employing the high power LED system, which has high thermal loss during the operating time. For this research, well designed thermoelement with heat radiation system was employed to enhance the collecting thermal energy from the LED system, and then convert it as recycled electrical energy.

P-Type ZnO Films Made by Atomic Layer Deposition and Ion Implantation.

Zinc oxide (ZnO) is a wide bandgap semiconductor that holds significant potential for various applications. However, most of the native point defects in ZnO like Zn interstitials typically cause an n-type conductivity. Consequently, achieving p-type doping in ZnO is challenging but crucial for comprehensive applications in the field of optoelectronics. In this work, we investigated the electrical and optical properties of ex situ doped p-type ZnO films. The p-type conductivity has been realized by ion implantation of group V elements followed by rapid thermal annealing (RTA) for 60 s or flash lamp annealing (FLA) on the millisecond time scale in nitrogen or oxygen ambience. The phosphorus (P)-doped ZnO films exhibit stable p-type doping with a hole concentration in the range of 1014 to 1018 cm-3, while antimony (Sb) implantation produces only n-type layers independently of the annealing procedure. Microstructural studies of Sb-doped ZnO show the formation of metallic clusters after ms range annealing and SbZn-oxides after RTA.

Navigating the future of solid oxide fuel cell: Comprehensive insights into fuel electrode related degradation mechanisms and mitigation strategies.

Solid Oxide Fuel Cells (SOFCs) have proven to be highly efficient and one of the cleanest electrochemical energy conversion devices. However, the commercialization of this technology is hampered by issues related to electrode performance degradation. This article provides a comprehensive review of the various degradation mechanisms that affect the performance and long-term stability of the SOFC anode caused by the interplay of physical, chemical, and electrochemical processes. In SOFCs, the most used anode material is nickel-yttria stabilized zirconia (Ni-YSZ) due to its advantages of high electronic conductivity and high catalytic activity for H2 fuel. However, various factors affecting the long-term stability of the Ni-YSZ anode, such as redox cycling, carbon coking, sulfur poisoning, and the reduction of the triple phase boundary length due to Ni particle coarsening, are thoroughly investigated. In response, the article summarizes the state-of-the-art diagnostic tools and mitigation strategies aimed at improving the long-term stability of the Ni-YSZ anode.

Optical and structural properties of Al-doped ZnO thin films by sol gel process.

Transparent conducting oxide (TCO) materials with high transmittance and good electrical conductivity have been attracted much attention due to the development of electronic display and devices such as organic light emitting diodes (OLEDs), and dye-sensitized solar cells (DSSCs). Aluminum doped zinc oxide thin films (AZO) have been well known for their use as TCO materials due to its stability, cost-effectiveness, good optical transmittance and electrical properties. Especially, AZO thin film, which have low resistivity of 2-4 x 10(-4) omega x cm which is similar to that of ITO films with wide band gap semiconductors. The AZO thin films were deposited on glass substrates by sol-gel spin-coating process. As a starting material, zinc acetate dihydrate (Zn(CH3COO)2 x 2H2O) and aluminum chloride hexahydrate (AlCl3 6H2O) were used. 2-methoxyethanol and monoethanolamine (MEA) were used as solvent and stabilizer, respectively. After deposited, the films were preheated at 300 degrees C on a hotplate and post-heated at 650 degrees C for 1.5 hrs in the furnace. We have studied the structural and optical properties as a function of Al concentration (0-2.5 mol.%).

Micro-fabrication of Piezo-composite materials on the flexible substrates.

In this study, we have presented micro-scaled flexible energy harvesters fabricated by the Micro-electromechanical systems (MEMS) process. The flexible energy harvesters were prepared by a pillar structure with a diameter size of 100-500 microm. We will describe a micro-pattern of fine scale ceramic structures utilizing an SU-8 negative photoresist by standard UV lithography. SU-8 processing was developed to implement low-stress SU-8 structures as permanent and functional material incorporated with silicon-on-insulator technologies. The micro-patterns of fine scale (Pb, Zr) TiO3 ceramics of the pillar shape were prepared by this MEMS method. We have studied the micro-pattern of fine scale PZT pillar structures through scanning electron microscope (SEM) analysis and several analysis methods.

Near infrared ray annealing effects on the properties of Al-doped ZnO thin films prepared by spin-coating method.

In this research, we will present Al doped ZnO thin films for transparent conducting oxide applications. Aluminum doped zinc oxide (AZO) thin films have been deposited on the glass substrates by sol-gel spin-coating method using zinc acetate dehydrate (Zn(CH3COO)2 2H2O) and aluminum chloride hexahydrate (AlCl3 x 6H2O) as cation sources. In this study, we investigated the effects of near infrared ray (NIR) annealing on the structural, optical and electrical characteristics of the AZO thin films. The experimental results showed that AZO thin films have a hexagonal wurtzite crystal structure and had a good transmittance higher than 85% within the visible wavelength region. It was also found that the additional energy of NIR helps to improve the electrical properties of Al doped ZnO transparent conducting oxides.

Rosen-Type Piezoelectric Transformers Based on 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 Ceramic and Doped with Sb2O3.

In this study, the characteristics in the lead-free piezoelectric ceramic 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (0.5BZT-0.5BCT) were investigated to assess its potential for Rosen-type piezoelectric transformers. This piezoelectric ceramic has a piezoelectric charge coefficient d33 of 430 pC/N, an electromechanical coupling factor kp of 49%, a dielectric constant εr of 2836, a remnant polarization Pr of 4.98 µC/cm2, and a coercive electric field Ec of 2.41 kV/cm. Sb2O3 was soft doped with 0.05, 0.1, 0.15, and 0.2 mol%, respectively, and exhibited excellent physical properties at 0.1 mol%. Based on this, a piezoelectric transformer was fabricated and measured, and it showed better output characteristics than pure 0.5BZT-0.5BCT. The amplification ratio (Vout/Vin) was optimized based on the device geometry and properties of the piezoelectric material. Moreover, the output characteristics of the Rosen-type piezoelectric transformer were simulated with the PSpice program. Output values of the fabricated and simulated piezoelectric transformers for the r vibrational frequency were compared and analyzed. Accordingly, the step-up amplification ratios Vout/Vin of the fabricated and simulated devices at the vibrational frequency were compared as well. This piezoelectric transformer could replace silicon steel transformers and be used for the creation of black light and for laptop chargers.

Effect of Contents on the Electrical and Piezoelectric Properties of (1 - x)(Bi, Na)TiO3-x(Ba, Sr)TiO3 Lead-Free Piezoelectric Ceramics.

In this study, the composition of lead-free piezoelectric ceramics (1 - x)(Bi0.5Na0.5)TiO3-x(Ba0.5Sr0.5)TiO3 with excellent piezoelectric properties was investigated. Crystal analysis and electrical and piezoelectric properties were analyzed according to the content of the BST composition. A phase change from rhombohedral to tetragonal structure was observed in 0.12 BST, and the densest and most uniform microstructure was confirmed in this composition. The dielectric constant increased from 905 to 1692 as the composition of BST increased to 0.12 BST. Afterward, as the composition of BST increased, the permittivity tended to decrease. Additionally, at 0.12 BST, Pr was the highest at 23.34 µC/cm2. The piezoelectric charge constant (d33) and the electromechanical coupling coefficient (kp) were 152 pC/N and 0.37, respectively, and showed the highest values at 0.12 BST. Curie temperature (Tm) was analyzed 242 °C at 0.12 BST, the optimal composition. It was confirmed that the characteristics of 0.12 BST were excellent in all conditions. Therefore, it was confirmed that 0.12 BST is the optimal composition for (1 - x)BNT-xBST piezoelectric ceramics.

Synthesis of a nitrogen doped reduced graphene oxide based ceramic polymer composite nanofiber film for wearable device applications.

In this study, piezoelectric composite nanofiber films were fabricated by introducing nitrogen-doped-reduced-graphene-oxide as a conductive material to a P(VDF-TrFE) polymer and a BiScO3-PbTiO3 ceramic composite employing an electrospinning process. Nitrogen was doped/substituted into rGO to remove or compensate defects formed during the reduction process. Electro-spinning process was employed to extract piezoelectric composite nanofiber films under self-poling condition. Interdigital electrodes was employed to make planner type energy harvesters to collect electro-mechanical energy applied to the flexible energy harvester. From the piezoelectric composite with interdigital electrode, the effective dielectric permittivity extracted from the conformal mapping method. By introducing BS-PT ceramics and N-rGO conductors to the P(VDF-TrFE) piezoelectric composite nanofiber films, the effective dielectric permittivity was improved from 8.2 to 15.5. This improved effective dielectric constant probably come from the increased electric flux density due to the increased conductivity. Fabricated interdigital electrode using this thin composite nanofiber film was designed and tested for wearable device applications. An external mechanical force of 350 N was applied to the composite nanofiber-based energy harvester with interdigital electrodes at a rate of 0.6 Hz, the peak voltage and current were 13 V and 1.25 µA, respectively. By optimizing the device fabrication, the open-circuit voltage, stored voltage, and generated output power obtained were 12.4 V, 3.78 V, and 6.3 µW, respectively.

Modeling of Optimized Lattice Mismatch by Carbon-Dioxide Laser Annealing on (In, Ga) Co-Doped ZnO Multi-Deposition Thin Films Introducing Designed Bottom Layers.

In this study, modeling of optimized lattice mismatch by carbon-dioxide annealing on (In, Ga) co-doped ZnO multi-deposition thin films was investigated with crystallography and optical analysis. (In, Ga) co-doped ZnO multi-deposition thin films with various types of bottom layers were fabricated on sapphire substrates by solution synthesis, the spin coating process, and carbon-dioxide laser irradiation with post annealing. (In, Ga) co-doped ZnO multi-deposition thin films with Ga-doped ZnO as the bottom layer showed the lowest mismatch ratio between the substrate and the bottom layer of the film. The carbon-dioxide laser annealing process can improve electrical properties by reducing lattice mismatch. After applying the carbon-dioxide laser annealing process to the (In, Ga) co-doped ZnO multi-deposition thin films with Ga-doped ZnO as the bottom layer, an optimized sheet resistance of 34.5 kΩ/sq and a high transparency rate of nearly 90% in the visible light wavelength region were obtained.

Enhanced Energy Efficiency of Light Grid System with Optimized System Design and Recycling with Thermoelectric Platform.

In this work, a light grid system with a high-power LED chip was manufactured and employed to analyze the energy efficiency of output optical energy. The high-power LED system based on thermoelectric modules, a heat dissipation structure and optical transmission system with an optical fiber were optimally combined and designed, which increased the efficiency of light grid system. Additionally, by introducing an effective design for the heat dissipation structure, the output optical energy and recycled electrical energy were increased. The recycled energy through optimized heat dissipation structure was 1.94 W, and the system efficiency of designed light grid system is more than 50%. In this research, we intensively studied the energy efficiency of a light grid system as well as the recycling of thermal energy through thermoelectric modules.

Improvement of Figure of Merit Pb(Zr,Ti)O3-Pb(Zn,Ni,Nb)O3-Pb(In,Nb)O3 Piezoelectric Ceramics.

Figure of merit the product of piezoelectric charge constant and the piezoelectric voltage constant-d33 × g33 in piezoelectric energy harvesting systems are critical measures in energy harvester applications. It is difficult to achieve high figure of merit because of the interdependence of d33 and the relative dielectric constant, εr. Until now, the prohibitive amount of effort required to solve this problem has led to it being considered an unsolvable issue. Lead zirconate titanate ceramic, Pb(Zr,Ti)O3, has been reported to exhibit high values of d33 and εr. However, to be employed as piezoelectric energy harvester, a candidate material is required to exhibit both high piezoelectric charge coefficient and high piezoelectric electric voltage coefficient simultaneously. To enhance the figure of merit of Pb(Zr,Ti)O3-based materials, dopants have also been considered. Pb(Zn,Ni,Nb)O3- added Pb(Zr,Ti)O3, Pb(Zr,Ti)O3-Pb(Zn,Ni,Nb)O3 ceramic has been reported to exhibit a high d33 value of 561 pC/N. It's dielectric constant has also been reported to be low at 1898. In this study, Pb(Zr,Ti)O3-Pb(Zn,Ni,Nb)O3-Pb(In,Nb)O3 was investigated in the context of enhancing the figure of merit of Pb(Zr,Ti)O3-based materials. During the proposed process, we increased the corresponding figure of merit by adding Pb(In,Nb)O3 material. Besides exhibiting a low dielectric constant, the Pb(In,Nb)O3 material was also observed to exhibit high d33 × g33 as the proposed doping increased the value of d33 greatly, while maintaining the dielectric constant (Yan, J., et al., 2019. Large engancement of trans coefficient in PZT-PZN energy harvesting system through introducing low εrPIN relaxor. Journal of the European Ceramic Society, 39, pp.2666-2672). Further, we conducted an optimization experiment by controlling the doping concentration and the sintering temperature.