In this study, we report the solid-state reaction synthesis of yttrium vanadate (YVO4)-based undoped and lanthanum (La)-doped powders. The photocatalytic performances, structural, morphological, and optical analyzes are presented. The X-ray diffraction analysis of samples indicates the crystalline tetragonal type crystal structure of YVO4 and no other lanthanum related impurity and/or secondary phases were detected. Photoluminescence analysis of samples show combined white light emission peaks that appeared at 478, 571 and 613 nm. To examine the photocatalytic activities, the degradation of methylene blue (MB) dye was monitored in the presence of these photocatalysts under the ultraviolet light irradiation. Pseudo-first-order reaction rate constant (k) of YVO4:La3+ (0.00846 min−1) is determined 66% greater than undoped one (0.00287 min−1). These results are compatible with the absorption spectra, as the energy band gap of the undoped photocatalyst was 3.8 eV while that of the doped one decreased to 3.54 eV.

In this research, phosphorescent SrAl 2 O 4 :Eu 2+ , Dy 3+ fibers were produced by electrospinning and coated with atomic layer deposition (ALD) technique to enhance the photoluminescence (PL) properties, and water & thermal resistance. Particle form of Eu 2+ -activated strontium aluminate phosphors possess many remarkable features that have been reported over and over, for example, nontoxic, stable, efficient. PL enhancement and stability in water of these particles were provided by nano encapsulation process by ALD that has just been published in our previous paper. In this study, for the first time, SrAl 2 O 4 based long persistence phosphor fibers were coated with the ALD method to both improve their PL and provide water & thermal resistance property. In this successfully carried out study, luminescence, optic, chemical and structural properties of phosphor in fiber form were investigated in detail. These improved submicron afterglow fibers which are SrAl 2 O 4 :Eu 2+ , Dy 3+ based are promising materials for applications such as solar cells, luminescent labels for bioimaging, mechanoluminescence sensor, etc.

In this study, piezoelectric based compressive type accelerometer has been de-signed by using PZT-5A ceramics with bellewasher type spring. FEA analysis were carried out by using COMSOL. According to COMSOL simulation, reso-nance frequency is nearly 42500 Hz. Sensitivity of the designed sensors were measured and compared each other. Frequency spectrum was between 100Hz-10 kHz. The effects of piezodisk thickness, stiffness of the spring and seismic mass on the sensitivity of the designed sensor were investigated. Voltage output is in-creasing from 4.1 mV/g to 12.7 mV/g while seismic mass is raised from 3 gr to 10 gr. Linearity depending on the frequency of the designed accelerometer was dis-torted above 5.5 kHz like commercial accelerometer. In addition, real-time tests were performed using a calibrated accelerometer and a designed accelerometer on the internal combustion engine and drivetrain. Vibration profiles were carried out randomly. According to the results obtained here, it is observed that all the peaks were matched with a coefficient about 1.3.

In the use of piezocermic applications, piezoceramic compositions have high d33 (>500 pC/N) and Kt (2000) such as PZT-5H. However, these ceramics can be sintered at high temperatures up to 1200˚C). Since these require the use of Ag-Pd inner electrodes with higher Pd ratio, multilayer ceramics are not preferred due to their high costs. In this study, it was aimed to reduce the sintering temperature without dramatically losing the electrical properties of the PZT-5H ceramics with high d33, kp and dielectric constant values. In this context, the PZT-5H composition was modified with different proportions of Li2CO3 and sintered for 2-4 hours at different sintering temperatures such as 875˚C-1250˚C depending on the ratio of additions. The piezoelectric and ferroelectric properties of the ceramics were investigated and obtained values were compared with undoped PZT-5H. It was observed that the d33 values of the different amount of Li2CO3 added compositions sintered at optimum sintering temperature are close that the composition without additives. In this way, it is predicted that 9/1 Ag/Pd and Ag inner electrode materials can be used in multilayer production and their costs can be reduced.

© 2020. The Author(s). This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (CC BY-NC 4.0, https://creativecommons.org/licenses/by-nc/4.0/deed.en which permits the use, redistribution of the material in any medium or format, transforming and building upon the material, provided that the article is properly cited, the use is noncommercial, and no modifications or adaptations are made. Arch. Metall. Mater. 65 (2020), 2, 609-614

In this study, lead-free 94Bi0,5Na0,5TiO3 -6BaTiO3 (94NBT-6BT) ceramics were fabricated by solidstate synthesis method at ambient atmosphere.Glassy phase and rounded particles in 94NBT-6BT was observed with increasing Mn content.The effects of doping manganese on the ferroelectric properties of 94NBT-6BT bulk ceramics were evaluated.From the XRD results of the calcined powders, peaks were slightly changed to higher 2 theta value while increasing manganese ratio.Multivalence additive Mn ions act as acceptor dopant in 94NBT-6BT structure at ambient atmosphere.Samples were sintered from 1075°C to 1175°C for 2 hours to obtain highest piezoelectric values.SEM results show that glassy phase and rounded particles in 94NBT-6BT was observed with increasing Mn content so, bulk density was enhanced up to 1125C.From the results, 0.3 wt% manganese doped 94NBT-6BT samples have highest electromechanical coupling factor about 0.23, mechanical coupling factor (Qm) 150 and d33 110 pC/N respectively.Further work, 94NBT-6BT and Mn-doped 94NBT-6BT multilayer actuators were manufactured by water-based tape casting technique.The active area was 49 mm 2 MLA and was fabricated by using Ag-Pd internal electrode without Pd-Bi reaction at the electrode-ceramic interface.Hysterisis loop measurements of manufactured lead free actuators were done by using Aixacct CMA module.Remnant polarization values of Mn-doped 94NBT-6BT MLA for a layer were higher than 6 µC/cm 2 .

Musculoskeletal disorders is one of most important health problems human population is facing includes. Approximately 310 thousand of hip protheses have been used in 45 years and older patients in ...

This study proposed a unique wideband energy harvester with a spiral metal plate design which has the potential to harvest vibrational energy over a broad range of ambient frequencies. In this design, metal shim with various length was integrated with piezoceramic rings in a spiral form as the cochlea. Spiral form metal shims with various radius leaves were integrated with piezoelectric ceramic. Each metal leaves has its resonance frequency that is slightly different than its neighboring ones. Parametric studies such as split structure, the radius of the metal shim, brass thickness, and tip mass and clamped area were performed to investigate the energy harvester structure. From the results, the buzzer form energy harvesting unit is designed to split leaf form, resonance frequency shifts to lower frequency. In split structure design for various leaf radius, every leaf keeps their resonance frequencies. This designed structure was resonated on the broader frequency range. Radius difference for neighbor leaves provided wider effective energy harvesting frequency range. Thicker brass shim led to higher stress on piezoelectric ceramic, more significant peak to peak output voltage at own resonance frequency.

A series of M2SiO4-based phosphors (M: alkaline-earth metal), (Ba,Ca)2SiO4: xEu, yMn, and zDy were synthesized by the solid-state reaction method. The XRD results showed all diffraction peaks of samples comply well with the T-phase (Ba,Ca)2SiO4, JCPDS#36-1449. Moreover, there were no obvious shifting of peaks or other impurity phases detected except that only higher levels of activator Eu-ion doping or Dy3+ co-doping among the current doping levels. The excitation spectrum of all samples shows a broad band and implies that these phosphors can be excited by the range UV region to 500 nm and may be recommended for white LEDs. The strong emission peaks observed in the red region, excited by 360 or 421 nm, corresponding to the 4T-6A forbidden transition of Mn2+ ions and weak peak of the blue to green broad emission bands observed at 466 nm is due to f-d transitions of Eu2+ ions. Also, it was proved that Dy3+ co-doping in different concentrations enhances the photoluminescence intensities.

Zr doped NBT-BZT(94Na 0.5 Bi 0.5 TiO 3 -6BaZr x T 1-x O 3 ) (x=0.1) powder was synthesis with solid-state method. The sintering process was carried out at between 1035 to 1180°C in air for 2h. The crystal phase and microstructure of the ceramics were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The influence of Zr content on the piezoelectric and energy harvesting performance were investigated and compared with PZT4, PZT5H. Ferroelectric and piezoelectric properties of NBT-BZT ceramics were obtained with impedance/gain phase analyzer. The results showed that, the best electrical properties were obtained at 1150°C. Also, energy harvesting potential of cymbal form of NBT-BZT materials were greater than disc (bulk) form.

Some of the piezoelectric devices work more efficiently around the resonance frequencies. Piezoelectric structures have the highest displacement and charge generation closer to the resonance conditions. In this study, a wide band energy harvester with a spiral metal plate was designed. Metal shim with various length were integrated with piezo ceramic rings in a spiral form. Each metal shim has its own resonance frequencies. Neighboring metal shim has also its own resonance frequency. Intriguingly, resonance frequency of each shim is close to each other to trigger each other vibration. With such a structure it will be possible to scavenge energy in vibrating structure with a wider frequency range. Resonance frequency of piezoelectric structures is depend on mass of piezoelectric ceramics and clamped metal shim geometry. Parametric studies were performed to investigate the optimal condition of such a structure.