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Photorefractive Materials
Published in Marvin J. Weber, and TECHNOLOGY, 2020
Carolina Medrano, Peter Günter
Potassium niobate and barium niobate are ferroelectrics with the perovskite structure. The diverse, strongly first-order phase transitions that occur between melting and room temperatures in KNbO3 and BaTiO3 make the preparation of large single-domain samples more difficult than for LiNbO3. Both crystals have enhanced photorefractive effects when iron is incorporated as an impurity in the melt. The charge transport parameters of these crystals are given in Table 11.1. In the case of KNbO3 the sensitivity of photovoltaic recording is several times larger than in a similarly doped crystals of LiNbO3. It can be seen from Table 11.1, that reduced KNbO3 yields an extremely large sensitivity for photoconductive recording. The dark conductivities σd are relatively large 10−9 < 10−13 (Ω cm)−1. These large ■ values cannot be explained by the Fe2+ concentration only. In oxidized samples, ionic conductivity may also have an important contribution.66 In slightly reduced crystals diffusion, photoconductivity, and the photovoltaic effect contribute similarly to the photorefractive effect in KNbO3 and their relative importance can be controlled by the fringe spacing or the applied electric field.67
Ceramic Capacitor Technology
Published in Lionel M. Levinson, Electronic Ceramics, 2020
Manfred Kahn, Darnall P. Burks, Ian Burn, Walter A. Schulze
In addition, the system Pb(Fe1/2Nb1/2)O3-Pb(Fe2/3W1/3)O3 with 3035 mol% lead iron tungstate has dielectric constants at 25°C of about 21,000 and sintering temperatures as low as 920°C (43). Addition of lead manganese niobate to this system decreases the dielectric losses. Excess niobium oxide improves its mechanical strength, and added lead zinc niobate aids densification. An even higher dielectric constant (34,000) has been reported for lead iron niobate with 18 mol% lead iron tungstate and 2% barium copper tungstate (44); the firing temperature was 900°C.
Polymer Nanogenerators for Biomedical Applications
Published in Inamuddin, Mohd Imran Ahamed, Rajender Boddula, Tariq Altalhi, Nanogenerators, 2023
Jaison Jeevanandam, Sharadwata Pan, Michael K. Danquah
Recently, Roy et al. (2019) developed a pyroelectric breathing sensor using a graphene oxide interfaced poly(vinylidene fluoride) nanofibers via electrospinning approach. The sensor possesses 4.3 V/kPa of high sensitivity to identify considerably low pressure (10 Pa), where the pyroelectric nanogenerator generates a maximum of ∼1.2 nW/m2 output power density to be beneficial for the fabrication of wearable sensors (Roy et al. 2019). Similarly, Ko et al. (2016) produced a hybrid piezoelectric-pyroelectric nanogenerator using a flexible film, made up of perovskite oxide of lead, zirconium, and titanium with nickel-chromium metal foil flexible substrate alongside lithium niobite (conductive), as the bottom electrode. The resultant nanogenerator exhibited 50 nC/cm2K and 140 pC/N of pyroelectric and piezoelectric coefficient, respectively, at room temperature. Furthermore, the nanogenerator generated stable electricity at a raised temperature of 100°C, 70% RH, and a stronger resistance for base and water even at a high Curie temperature (Ko et al. 2016). Likewise, Yang, Jung, et al. (2012) synthesized tunable pyroelectric nanogenerators via an amalgamated configuration of potassium niobate (devoid of lead) nanowires. In this study, the direction poling process was used for manufacturing the nanowires (devoid of lead) alongside a sing crystalline structure, and formed as a composite with polydimethylsiloxane polymer to be beneficial as a potential pyroelectric nanogenerator. The study emphasized that the resultant nanogenerator can utilize electric field for controlling the voltage or the current output, which can be eventually increased by the alterations in temperature (Yang, Jung, et al. 2012). Thus, it is apparent that several novel synthesis approaches are utilized for the fabrication of pyroelectric and hybrid nanogenerators with pyroelectric properties.
Controllable antimicrobial properties of silver ion-exchanged niobate and tantalate compounds
Published in Journal of Asian Ceramic Societies, 2022
Withanage Isuru Udakara Withanage, Kuda Durayalage Sulasa Devi Ariyapala, Nobuhiro Kumada, Takahiro Takei, Mayu Ueda, Mamoru Aizawa
The variety of techniques, such as wet chemical methods, sol-gel methods, thermal or cold spraying techniques, ion-exchange methods, and doping or loading methods, are used to synthesize Ag-containing antibacterial materials [20–22]. Among these methods, the ion-exchange method has been proven to be a simple way to regulate the amount of silver content in potassium tantalate (KT) and potassium niobate (KN) with the pyrochlore-type structure [23]. Although many studies have focused on Ag-containing antibacterial materials, to the best of our knowledge, there have been no studies on the antibacterial properties of Ag-incorporated pyrochlore-type niobate and tantalate compounds. In this study, Ag ions were incorporated into KN and KT structures using small molar ratios and gradually increased to obtain completely ion-exchanged samples. Our aim was to obtain controllable antibacterial properties employing these different ion-exchanged compounds and compare their efficiency against E. coli and S. aureus using the colony count method and inhibition zone method.
Studies on the combined effects of titania and silicon carbide on the phase developments and properties of carbon-clay based ceramic composite
Published in Cogent Engineering, 2019
Fatai Olufemi Aramide, O. D. Adepoju, Adeolu Adesoji Adediran, Abimbola Patricia Popoola
Ebadzadeh and Ghasemi (Ebadzadeh & Ghasemi, 2002) produced zirconia mullite composites from α-alumina, aluminium nitrate, zircon powder with TiO2 additive. Aramide et al. (Aramide, Alaneme, Olubambi, & Borode, 2014) synthesized mullite-yttria stabilized zirconia composites. Chandra et al. (Chandra, Das, Sengupta, & Maitra, 2013) synthesized zirconia-toughened ceramics with a mullite matrix based on the quaternary system ZrO2–Al2O3–SiO2–TiO2 in the temperature range 1450–1550°C using zircon-alumina-titania mixtures. Aramide and Popoola (Aramide & Popoola, 2017) investigated the effects of niobium oxide additive on phase development and physico-mechanical properties of zirconia-clay based ceramic composite. They discovered that niobium oxide additive inhibits mullite formation in preference to aluminium niobate and sillimanite.
Wave propagation analysis of smart inhomogeneous piezoelectric nanosize beams rested on an elastic medium
Published in Waves in Random and Complex Media, 2022
In this paper, wave dispersion responses of sigmoid FGP nanobeam resting on an elastic medium are investigated for the first time. Zinc oxide and Lithium niobate are assumed to be constituent materials of sigmoid FGP nanobeam. Moreover, small-scale effect is considered by using ENET. Electromechanical properties of nanobeam vary continuously through the thickness direction and also the effective properties are computed via sigmoid law. In order to attain the nonlocal governing equations, classic beam theory and Hamiltonian approach are exerted. Eventually, the effect of various variants that is indicated can be observed in detail.