Effect of the addition of Ca2+ on the structure, microstructure and ferroelectric properties of (Pb1 − y Ca y )(Zr0.8Ti0.2)O3 system with y = 0.0, 0.02, 0.05 and 0.1

This work studies the relationship between ferroelectric properties and structural features of the (Pb_{1 – y} Ca _y )(Zr_0.8Ti_0.2)O₃ system with y = 0.0, 0.02, 0.05 and 0.1. All of the samples were prepared by hot-pressing of PZT calcined powder, prepared by conventional ceramic route. Single phase compositions of rhombohedral (RH) structure were observed for the whole series of the samples studied in this work. However, a linear decrease of RH lattice constant a _p is seen with increasing the Ca²⁺ concentration with a subsequent decrease of lattice strain expressed by (90 – _p). Further, a sharp decline is also observed in the magnitudes of saturation polarization (P _s) of the samples doped with 2 mol% Ca²⁺. However, the rate of decrease slows down for Ca²⁺ concentrations above this level. A diffuse phase transition was observed in the case of 10 mol% Ca²⁺-doped PZT(0.8) which is believed to be possibly due to the distribution in coupling strengths created from a random compositional fluctuations of Ca²⁺ and Pb^2– ions on A-sites. The results are interpreted on crystal-chemical grounds. It is proposed that the long range coupling of (Zr/Ti)O₆ coordination octahedra and Pb²⁺ ions, due to the covalency of the Pb–O bond, is interrupted by the incorporation of Ca²⁺. By considering the effect of calcium on coupling strength and coupling distribution, the observed dielectric response for the above compositions is qualitatively explained.     

Effect of the addition of Y2O3 on the structure, microstructure and piezoelectric properties of PZT(53/47)

In this work, an attempt is made to study system with x=0.0125, 0.025, 0.050, 0.075 and 0.1. It was shown that there is limited solid solubility (0.625 mol %) of or 1.25 mol % of in PZT(53/47). For higher levels of dopant, mainly two other extra second phases were detected. The first was a Zr-rich phase in which some and small amounts of was dissolved. The second one was a Pb solid solution composed of mainly PbO, and which was initially also seen in calcined samples. The formation of Zr-rich phase is thought possibly to originate due to the sublimation of Pb from source during the sintering process. For higher x values, a structural shift towards Ti-rich region of PZT's phase diagram is seen. All piezoelectric parameters of the doped samples such as , are seen to decline sharply compared to that of undoped samples. Increasing the level of dopant gave rise to the increase of conductivity and dielectric loss of sintered samples. The formation of non-ferroelectric extra phases, and the Zr/Ti change of the main formed phase is believed to be responsible for this behavior.     

Electrocatalytic and simultaneous determination of isoproterenol, uric acid and folic acid at molybdenum (VI) complex-carbon nanotube paste electrode

This paper describes the development, electrochemical characterization and utilization of a novel modified molybdenum (VI) complex-carbon nanotube paste electrode for the electrocatalytic determination of isoproterenol (IP). The electrochemical profile of the proposed modified electrode was analyzed by cyclic voltammetry (CV) that showed a shift of the oxidation peak potential of IP at 175 mV to less positive value, compared with an unmodified carbon paste electrode. Differential pulse voltammetry (DPV) in 0.1 M phosphate buffer solution (PBS) at pH 7.0 was performed to determine IP in the range from 0.7 to 600.0 μM, with a detection limit of 35.0 nM. Then the modified electrode was used to determine IP in an excess of uric acid (UA) and folic acid (FA) by DPV. Finally, this method was used for the determination of IP in some real samples.     

Effect of sintering temperature on the microstructure and high-frequency magnetic properties of Ni0.467Zn0.07Co0.015Fe0.511O4 ferrite

In this work, an attempt is made to study the effects of sintering temperature on the microstructure and high-frequency (HF) magnetic properties of a nickel zinc ferrite compound of very low ZnO content of Ni_0.467Zn_0.07Co_0.015Fe_0.511O₄ composition. Samples were prepared by a conventional ceramic route and sintered for 2 h at 1150, 1200, 1250, and 1300 °C. It was shown that the higher the sintering temperature the higher the saturation magnetization and the measured initial permeabilities, and the lower was the H _c of the samples. This was related to the increased sintered densities and grain sizes. The magnitudes of the electrical resistivity of the samples sintered at 1300 °C compared to those of the samples sintered at 1150 °C and 1200 °C showed four orders decrease. This is thought to be due to the grain-size increase and possibly the formation of higher Fe²⁺/Fe³⁺ concentration. The lowest measured quality factor (Q-factor) obtained in the range of 60–210 MHz, corresponds to the samples sintered at 1300 °C. The highest Q-value in the frequency range of 125–210 MHz was obtained for the samples sintered at 1150 °C, which has also shown the highest electrical resistivity.     

A voltammetric sensor for the detection of 2-aminophenol in the presence of bisphenol A using a carbon paste electrode modified with N-doped reduced graphene oxide/CuO nanocomposite and ionic liquid

Journal of Materials Science: Materials in Electronics - In present work, a novel and facile electrode was constructed using the modification of carbon paste electrode (CPE) with N-doped reduced...     

Fe2MoO4 magnetic nanocomposite modified screen printed graphite electrode as a voltammetric sensor for simultaneous determination of nalbuphine and diclofenac

Journal of Materials Science: Materials in Electronics - This study applied screen printed graphite electrode (SPGE) modified with the Fe2MoO4 magnetic nanocomposite for simultaneously determining...     

Electrochemical sensor for selective determination of N-acetylcysteine in the presence of folic acid using a modified carbon nanotube paste electrode

In the present paper, a novel benzoylferrocene (BF) modified carbon nanotube paste electrode (BFCNPE) was prepared. The modified electrode was further used for the successful determination of N-acetylcysteine (NAC), and it showed an excellent electrocatalytic oxidation activity toward NAC with a lower overvoltage, pronounced current response, and good sensitivity. Under the optimized experimental conditions, the proposed electrochemical NAC sensor exhibited a linear calibration plot that ranged from 3.0 × 10^? 7 to 7.0 × 10^? 4 M with a detection limit of 9.0 × 10^? 8 M. Also, Square wave voltammetry (SWV) was used for simultaneous determination of NAC and folic acid (FA) at the modified electrode. Finally, the proposed method was applied to the determination of NAC in NAC tablets.     

Selective voltammetric determination of norepinephrine in the presence of acetaminophen and tryptophan on the surface of a modified carbon nanotube paste electrode

A new electrochemical sensor for the determination of norepinephrine (NE), acetaminophen (AC) and tryptophan (TRP) is described. The sensor is based on carbon paste electrode (CPE) modified with 5-mino-3′,4′-dimethyl-biphenyl-2-ol (5ADB) and takes the advantages of carbon nanotubes (CNTs), which makes the modified electrode highly sensitive for the electrochemical detection of these compounds. Under the optimum pH of 7.0, the oxidation of NE occurs at a potential about 170 mV less positive than that of the unmodified CPE. Also, square wave voltammetry (SWV) was used for the simultaneous determination of NE, AC and TRP at the modified electrode.     

An electrochemical sensor based on 1-benzyl-4-ferrocenyl-1H-[1,2,3]-triazole/carbon nanotube; detection of D-penicillamine in the presence of tryptophan

A glassy carbon electrode modified with 1-benzyl-4-ferrocenyl-1H-[1,2,3]-triazole (BFT) and carbon nanotubes have been applied to the electrocatalytic oxidation of D-penicillamine (D-PA) which reduced the overpotential by about 470 mV with obviously increase the current response. Due to its strong electrocatalytic activity towards D-PA, the modified electrode can resolve the overlapped voltammetric waves of D-PA and tryptophan (TRP) into two well-defined voltammetric peaks with peak-to-peak separation in potentials of about 270 mV. This property allows to selective determination of D-PA in the presence of TRP. The transfer coefficient (a) for the electrocatalytic oxidation of D-PA and diffusion coefficient of this substance under the experimental conditions were also investigated. In phosphate buffer solution (PBS) of pH 8.0, the oxidation current increased linearly with two concentration intervals of D-PA, one is 1.0 to 10.0 μM and, the other is 10.0 to 800.0 μM. The detection limit (3σ) obtained by square wave voltammetry (SWV) was 0.1 μM. The proposed method was successfully applied to the determination of D-PA, and TRP in real samples.     

Voltammetric determination of norepinephrine in the presence of acetaminophen using a novel ionic liquid/multiwall carbon nanotubes paste electrode

A novel multiwall carbon nanotubes (MWCNTs) modified carbon ionic liquid electrode (CILE) was fabricated and used to investigate the electrochemical behavior of norepinephrine (NP). MWCNTs/CILE was prepared by mixing hydrophilic ionic liquid, 1-methyl-3-butylimidazolium bromide (MBIDZBr), with graphite powder, MWCNTs, and liquid paraffin. The fabricated MWCNTs/CILE showed great electrocatalytic ability to the oxidation of NE. The electron transfer coefficient, diffusion coefficient, and charge transfer resistant (R_ct) of NE at the modified electrode were calculated. Differential pulse voltammetry of NE at the modified electrode exhibited two linear dynamic ranges with slopes of 0.0841 and 0.0231 μA/μM in the concentration ranges of 0.3 to 30.0 μM and 30.0 to 450.0 μM, respectively. The detection limit (3σ) of 0.09 μM NP was achieved. This modified electrode exhibited a good ability for well separated oxidation peaks of NE and acetaminophen (AC) in a buffer solution, pH 7.0. The proposed sensor was successfully applied for the determination of NE in human urine, pharmaceutical, and serum samples.