Rashed Adnan Islam

Realization of high-energy density polycrystalline piezoelectric ceramics

This letter reports a high energy density piezoelectric material in the system given as: Pb[(Zr0.52Ti0.48)O3]1−x[(Zn1∕3Nb2∕3)O3]x+yMnCO3, where x=0.1 and y varies from 0.5to0.9wt%. A piezoelectric material with high energy density is characterized by a high product of piezoelectric voltage constant (g) and piezoelectric strain constant (d). The condition for obtaining large magnitude of g constant was derived to be as ∣d∣=en, where e is the permittivity of the material and n is constant having lower bound of 0.5. It was found that for all practical polycrystalline piezoelectric ceramic materials the magnitude of n lies in the range of 1.1–1.30 and as the magnitude of n decreases towards unity a giant enhancement in the magnitude of g was obtained. A two step sintering process was developed to optimize a polycrystalline ceramic composition with low magnitude of n. For the optimized composition the value of g33 and d33 was found to be 55.56×10−3m2∕C and 291×10−12C∕N, respectively, yielding the magnitude pro...

Giant magnetoelectric effect in sintered multilayered composite structures

Trilayer composites consisting of 0.9Pb(Zr0.52Ti0.48)O3–0.1Pb(Zn1/3Nb2/3)O3 (0.9 PZT-0.1 PZN) and Ni0.6Cu0.2Zn0.2Fe2O4 (NCZF) in the configuration NCZF-(0.9 PZT-0.1 PZN)-NCZF were synthesized using pressure assisted sintering. Composites with optimized magnetostrictive to piezoelectric thickness ratio showed a high magnetoelectric (ME) coefficient of 525 mV/cm Oe. Further enhancement in the magnitude of ME coefficient was obtained (595 mV/cm Oe) when the angle of applied dc magnetic field was changed to 45°. Changing the intermediate piezoelectric layer from single to trilayer stack geometry configuration leads to the realization of giant ME response of 782 mV/cm Oe in sintered composites.

Characterization of Mechanical and Electrical Properties of Epoxy-Glass Microballoon Syntactic Composites

The density of hollow particle (microballoon) filled composites called syntactic foams can be varied by two methods. The first method is the variation in microballoon volume fraction and the second method is the variation in the microballoon wall thickness, while keeping their volume fraction the same. A comparison of compressive properties of syntactic foams having microballoons of four different wall thicknesses in five volume fraction each is presented here. It is found that the compressive strength and modulus vary linearly with respect to the foam density. Dielectric constant, dielectric loss and electrical impedance are measured for four syntactic foam compositions with respect to temperature and frequency. Dielectric constant and loss are found to decrease with increase in frequency and with decrease in temperature in the range of 40–140°C.

Magnetoelectric properties of the lead–free cofired BaTiO3–(Ni0.8Zn0.2)Fe2O4 bilayer composite

In this letter the authors report the ferroelectric and magnetoelectric (ME) properties of the cofired bilayer composite targeting low cost lead-free magnetic field sensor. The ME response was characterized as a function of the magnetic field direction and as a function of the dc bias. It was found that when the ac magnetic field is applied at 90° to the ferroelectric polarization axis of the sample, a ME response of 72mV∕cmOe was obtained without any dc bias. The magnitude of the ME coefficient reached the saturation at dc bias of 1000Oe having magnitude of 152mV∕cmOe. The scanning electron microscopy analysis showed the presence of clear interface boundary between the strained BaTiO3∕(Ni0.8Zn0.2)Fe2O4 region.

Laser-machined piezoelectric cantilevers for mechanical energy harvesting

In this study, we report results on a piezoelectric- material-based mechanical energy-harvesting device that was fabricated by combining laser machining with microelectronics packaging technology. It was found that the laser-machining process did not have significant effect on the electrical properties of piezoelectric material. The fabricated device was tested in the low-frequency regime of 50 to 1000 Hz at constant force of 8 g (where g = 9.8 m/s2). The device was found to generate continuous power of 1.13 muW at 870 Hz across a 288.5 kOmega load with a power density of 301.3 muW/cm3.

Electric energy generator

This study reports an extremely cost-effective mechanism for converting wind energy into electric energy using piezoelectric bimorph actuators at small scale. The total dimensions of the electric energy generator are 5.08 times 11.6 times 7.7 cm3. The rectangular, box-shaped body of the overall structure is made using 3.2-mm thick plastic. Slits are made on two opposite faces of the box so that two columns and six rows of bimorph actuators can be inserted. Each row of bimorph actuators is separated from each other by a gap of 6 mm, and the two columns of bimorphs are separated from each other by a gap of 6.35 mm. In between the two columns, a cylindrical rod is inserted consisting of six rectangular hooks. The hooks are positioned in such a way that each of them just touches the two bimorphs on either side in a particular row. As the wind flows across the generator, it creates a rotary motion on the attached fan that is converted into vertical motion of the cylindrical rod using the cam-shaft mechanism. This vertical motion of the cylindrical rod creates oscillating stress on the bimorphs due to attached hooks. The bimorphs produce output voltage proportional to the applied oscillating stress through piezoelectric effect. The prototype fabricated in this study was found to generate 1.2 mW power at a wind speed of 12 mph across the load of 1.7 kOmega

Annealing and Aging Effect in 0.95 Pb(Zr0.52Ti0.48)O3–0.05 NiFe1.9Mn0.1O4 Particulate Magnetoelectric Composites

The results in this letter show the possibility of realizing a high magnetoelectric (ME) coefficient material by synthesizing the particulate composites of ferroelectric and ferromagnetic components using the annealing and aging treatment. The ME composites were fabricated using a combination of conventional mixed oxide sintering and thermal treatment. The thermal treatment constituted of annealing at temperature closer to calcination temperature (~800°C) followed by aging at lower temperatures (300–400°C). Microstructure of the fabricated samples was analyzed using the X-ray mapping in scanning electron microscopy (SEM) and it was found that NiFe1.9Mn0.1O4 (NFM) is distributed inside the Pb(Zr0.52Ti0.48)O3 (PZT) grains on the length scales of 100 nm. The magnitude of piezoelectric constant (d33) and the dielectric constant exhibited significant variation with aging time and temperature. It was found that the magnitude of ME coefficient for PZT–5NFM sample increased from 37 to 56 mV/cmOe after thermal treatment, an enhancement of ~50%.

Magnetoelectric properties of core-shell particulate nanocomposites

In this study, we report results on magnetoelectric (ME) core-shell Pb(Zr,Ti)O3 (PZT)-NiFe2O4 (NF) particulate nanocomposites. NF particles forming the shell had size in range of 20–30 nm. The grain size of sintered nanocomposites was found to be in the range of 500–800 nm. The sintered nanocomposite exhibited piezoelectric coefficient (d33) of 60 pC/N, dielectric constant of 865, and ME coefficient of 195 mV/cm Oe. High ME coefficient was observed for wide range of dc bias magnetic field. This approach of fabricating layered composite has a promise to provide large ME coefficients in particulate sintered structures.

Progress in Dual (Piezoelectric-Magnetostrictive) Phase Magnetoelectric Sintered Composites

The primary aims of this review article are (a) to develop the fundamental understanding of ME behavior in perovskite piezoelectric-spinel magnetostrictive composite systems, (b) to identify the role of composition, microstructural variables, phase transformations, composite geometry, and postsintering heat treatment on ME coefficient, and (c) to synthesize, characterize, and utilize the high ME coefficient composite. The desired range of ME coefficient in the sintered composite is 0.5–1 V/cm⋅Oe. The studies showed that the soft piezoelectric phase quantified by smaller elastic modulus, large grain size of piezoelectric phase (~1 μm), and layered structures yields higher magnitude of ME coefficient. It is also found that postsintering thermal treatment such as annealing and aging alters the magnitude of magnetization providing an increase in the magnitude of ME coefficient. A trilayer composite was synthesized using pressure-assisted sintering with soft phase [0.9 PZT–0.1 PZN] having grain size larger than 1 μm and soft ferromagnetic phase of composition Ni0.8Cu0.2Zn0.2Fe2O4 [NCZF]. The composite showed a high ME coefficient of 412 and 494 mV/cm⋅Oe after sintering and annealing, respectively. Optimized ferrite to PZT thickness ratio was found to be 5.33, providing ME coefficient of 525 mV/cm⋅Oe. The ME coefficient exhibited orientation dependence with respect to applied magnetic field. Multilayering the PZT layer increased the magnitude of ME coefficient to 782 mV/cm⋅Oe. Piezoelectric grain texturing and nanoparticulate assembly techniques were incorporated with the layered geometry. It was found that with moderate texturing, d33 and ME coefficient reached up to 325 pC/N and 878 mV/cm⋅Oe, respectively. Nanoparticulate core shell assembly shows the promise for achieving large ME coefficient in the sintered composites. A systematic relationship between composition, microstructure, geometry, and properties is presented which will lead to development of high-performance magnetoelectric materials.

Piezoelectric transformer based ultrahigh sensitivity magnetic field sensor

Magnetoelectric particulate composites with varying ferrite content (3–20mol%) were synthesized in the system Pb(Zr0.52Ti0.48)O3 (PZT)–Ni0.8Zn0.2Fe2O4 (NZF) and it was found that 0.8PZT-0.2NZF composite material exhibited high response of the order of 450mV∕cmOe at the low frequency of 1kHz with 600Oe dc bias. This is one of the highest magnitudes reported for the sintered particulate composite materials. This material was used to fabricate a magnetic field sensor which utilizes the piezoelectric transformer structure with ring/dot electrode pattern. The size of the magnetic field sensor was ϕ20×1.5mm2. The sensor was characterized for the changes in the output voltage and resonance frequency shift under constant current condition. A dramatic change in the magnitude of the output voltage and frequency shift was observed on application of the magnetic field. The sensor design presented in this letter clearly shows the possibility of fabricating an extremely cost-effective magnetometer.