Doped Specimens Research Articles

Effect of Sn or Ta doping on the microstructure and total conductivity of perovskite Li0.24La0.587TiO3 solid electrolyte

Perovskite-structured Sn- or Ta-doped Li0.24–(q–4)xLa0.587Ti1–xMxO3 (LLTMxO, M = Sn or Ta, q is equal to the valence of M, x = 0, 0.02, 0.04, 0.06, 0.08) solid electrolytes are prepared by the pressureless sintering method for Li ion batteries. The phase composition, microstructure and electrical performance as a function of the type of doping elements and the amounts corresponding are studied by XRD, Raman spectrometer, SEM and electrochemical impedance spectroscopy. The LLTMxO pellets sintered at 1350 °C for 12 h have high relative densities (96.2%–97.9%) and high conductivities, where the total conductivity of LLTTa0.04O and LLTSn0.02O reach 4.09 × 10−4 S cm−1 and 2.98 × 10−4 S cm−1 at room temperature (RT) respectively. Compared with the pure specimen (1.52 × 10−4 S cm−1), the total conductivities of the doped specimens are more than doubled. In addition, Sn or Ta doping can significantly reduce the activation energy, with LLTTa0.04O exhibiting the low activation energy of 0.31 eV. The improvement in the total conductivity is attributed to the expansion of the Li ion transmission channels, the improvement of the relative density and the rise in the Li ion vacancy concentration, which are all resulted from the effect of dopant.

Synthesis, characterization, and performance evaluation of pristine and cerium‐doped WO3 nanoparticles for photodegradation of methylene blue via solar irradiation

AbstractIn this study, an effective photodegrading properties of WO3 nanoparticles has been enhanced by doping with cerium. To achieve our goal pristine and Ce‐doped WO3 nanoparticles were prepared by a simple and cost effective co‐precipitation route. Characterization of all the specimens were conducted which showed that there were no noticeable structural changes. WO3 retained its monoclinic structure even after doping with (3%, 5%, 8%, 10%) cerium which was also confirmed with X‐ray diffraction (XRD) and Raman spectroscopy. In addition, XRD and Fourier transform infra‐red spectroscopy also confirm that no new phases were formed in doped specimens. XRD also depicts that minimum crystallite size is achieved at 3% cerium doping. Scanning electron microscope images show decrease in particle size initially at 3% cerium doping, that is, ~80 ± 2.5 nm. In contrast, further increase in doping percentage increases crystallite and particle sizes. Additionally, defect generation increased at lower doping percentage ~3%. In contrast, further increase in dopant (5%, 8%, 10%) caused defect annihilation process to dominate over defect generation. C/Co ratio and rate constant (KMB) values suggest that maximum degradation of methylene blue will occur at 3% cerium doping due to increase in crystalline defects. Ultraviolet visible Spectroscopy further validates C/Co ratio and degradation rate constant values by showing drastic decline in peak intensity at 3% cerium doping. Therefore, 3% cerium‐doped WO3 is more effective photocatalyst to degrade methylene blue in comparison to most of the previously used photocatalysts. The prepared cerium‐doped WO3 nanoparticles as a sun light driven photocatalyst, may be utilized for industrial wastewater purification.

Densification behavior and microstructure development in TiB2 ceramics doped with h-BN

This paper aims to study the impacts of h-BN additive on the microstructural features and sintering behavior of TiB2. For this objective, two different samples of monolithic TiB2 and TiB2-5 wt% h-BN were fabricated using spark plasma sintering (SPS) technique at 1900 °C. An external pressure of 40 MPa was exerted to the specimens during the sintering, and they were maintained at the maximum sintering temperature for 7 min. The characterization of as-fabricated ceramics was carried out using thermodynamical investigations, field emission SEM, and X-ray diffractometer. The thermodynamical and XRD studies revealed that the sintering process was non-reactive for both samples. However, introducing h-BN noticeably promoted the sinterability of TiB2 through activating the liquid phase sintering mechanism, and a near-fully dense composite was attained. The fractographical assessment manifested that the intergranular fracture was the dominant type in both monolithic and h-BN doped specimens. Finally, the quantitative image analysis indicated the role of h-BN in refining the microstructure of the doped TiB2 ceramic.

Behavioural response of cells and bacteria on single and multiple doped Sr and Ag S53P4 sol-gel bioglass

The aim of this study is to investigate the response of cells and bacteria on Sr, Ag, and Sr + Ag doped S53P4 sol-gel bioglass. In this study, 3 mol% of SrO and 1 mol% of Ag2O were selected as doping for single and multiple doped S53P4 sol-gel bioglass. These doped specimens were denoted as BG, BG-3S, BG-1A, and BG-3S1A throughout the study. Cell study showed that the BG-3S1A specimen exhibited the highest proliferation of MC3T3-E1 osteoblast-like cells, ALP activity, and bone nodule formation in comparison with other specimens. Meanwhile, antibacterial study of the BG-3S1A specimen showed relatively similar antibacterial responses towards Escherichia coli and Staphylococcus aureus in comparison with the BG-1A specimen. Therefore, these findings proved that by combining appropriate amount of Sr and Ag doping ions into S53P4 bioglass composition, cellular proliferation and antibacterial response could be stimulated, which could benefit patients who suffer from bacteria-infected bone defect diseases.

Influence of Y2O3 and Ta2O5 Co-doping on Microstructure and Thermal Conductivity of Gd2Zr2O7 Ceramics

Rare earth zirconates (RE2Zr2O7) are considered as a class of potential high-temperature structural materials. In this paper, a series of Y2O3 and Ta2O5 co-doped Gd2Zr2O7 [(Gd1−xYx)2(Zr1−xTax)2O7+x, x = 0, 0.1, 0.2, 0.3, 0.4] ceramics were prepared by solid-state reaction sintering in order to clarify the influence of Y2O3 and Ta2O5 co-doped on microstructure, Young’s modulus and thermal conductivity. The results showed that Y2O3 and Ta2O5 co-doped Gd2Zr2O7 exhibited a single pyrochlore structure, and a small amount of Y3+ ions were doped into the Zr4+ ions lattice. The Young’s moduli of doped Gd2Zr2O7 ceramics slightly change with the increase in Y2O3 and Ta2O5 doping concentration. The minimum thermal conductivities of the specimens were obtained at 800 °C. The thermal conductivity of doped Gd2Zr2O7 with x = 0.3 is lower than that of others among the doped specimens, which is around 1.41 W m−1 K−1 at 800 °C. In addition, (Gd0.7Y0.3)2(Zr0.7Ta0.3)2O7.3 ceramic exhibits excellent phase stability from room temperature to 1550 °C.

Pd Dopant for SnO2 Based Thick Film Gas Sensor for Detection of LPG using ANN Technique

In the present paper, studies that it has been made to investigate the sensitivity, response of SnO2 based different Pd-doped thick gas sensor for LPG detection using different non-linear ANN technique at temperature of 350° C. Thick film SnO2 sensor is fictitious on a 1” x 1” alumina substrate. It consists of a SnO2 doped hypersensitive gas layer including different Pd, a pair of electrodes bottom the gas sensing layer serving as a contact pad for sensor. In conjunction with a heater, element designed on the backside of the substrate was printed. The sensitivity of sensor has been studied at different Pd-doped concentration upon exposure LPG for finding the maximum sensitivity at a temperature at 350 c. on the pair of pure and pd doped specimen analysis of conductance and capacitance have been invented by fixed temperature at fixed gas concentration .the sensor sensitivity has been studied at different pd doped at constant temperature of 350° C upon exposure to LPG. The sensitivity and selectivity measurement of sensing ownership are carried out in the range 0- 5000 ppm at 350° C. The maximum response of 72.08% at 350° C was obtained under the explore of 0.5% of LPG. Practical sensitivity of LPG is used to measure the sensitivity of different Pd-doped SnO2 based thick film gas sensors by using ANN algorithm. The performance of ANN models with different non- linear algorithm is evaluated on practical sensitivity of sensor with different network transfer functions. Experimentally, we found that ANN model training algorithm is more suitable for the sensor and sensitivity. ANN as an effective tool in the area of SnO2 based thick film sensor design to find the sensitivity of the LPG gas.

Effect of doping on nanoindentation induced incipient plasticity in InP crystal

This article is concerned with incipient plasticity in an InP crystal studied by nanoindentation experiments and ab initio simulations. We consider dislocation-nucleation phenomena and pressure-induced phase transformation to be the alternative mechanisms that govern the elastic-plastic transition displayed by the InP crystal. The ab initio calculations have shown that S- and Zn-doping of the low-pressure zinc blende structure of InP decreases the pressure of phase transformation of the rock-salt structure. The nanoindentation examination of undoped as well as S- and Zn-doped crystals of (001) and (111) orientation revealed an increase in contact pressure at the onset of plastic behavior (pop-in) for doped specimens. As they are contrary to the outcomes of the ab initio simulations, the results of nanoindentation experiments point toward dislocation nucleation as an origin of InP incipient plasticity. Additional investigations were performed on an undoped as well as Si-doped GaAs crystal, which showed that the contact pressure at the pop-in event takes a lower value for the Si-doped sample than the undoped sample. This result is in contrast to the case of the InP crystal displaying phase transformation-steered incipient plasticity of GaAs. Our investigations exhibit the complexity of the semiconductor’s nanodeformation simultaneously providing a convenient way to identify its incipient plasticity mechanism.

Bulk Yttria as a Host for Lanthanides in Biomedical Applications: Influence of Concentration Gradients on Structural, Mechanical, Optical, and in Vitro Imaging Behavior

The biomedical application of yttria (Y2O3) as a bulk material to host a series of rare earth elements (RE3+) has been explored in the current investigation. Dy3+, Gd3+, Tb3+, Yb3+, Eu3+, and Nd3+ were chosen for this purpose, and their corresponding concentrations in Y2O3 have been varied to obtain five different combinations. The results ascertain the potential of Y2O3 to host different RE3+ to retain a discrete cubic yttria (c-Y2O3) devoid of significant structural distortion until 1400 °C. Depending upon the size of RE3+, either a contracted or expanded cubic Y2O3 unit cell has been determined from the XRD and Raman analyses. Other than the typical vibrational modes of c-Y2O3, Raman spectra also unveiled characteristic emission features of RE3+ that were dependent on the excitation laser used to record the spectra. The characteristic absorption and emission characteristics depending on the type of RE3+ substitutions were determined from the optical measurements. Pore free microstructures determined from the morphological analysis are reflected in the enhanced mechanical behavior of RE3+ doped Y2O3 specimens. Dy3+ and Yb3+ substituted Y2O3 unveiled computed tomography (CT) imaging features. Dy3+, Tb3+, and Nd3+ dopant compositions delivered T2 magnetic resonance imaging (MRI) contrast features, while the specimen comprising Gd3+ revealed both T1 and T2 MRI characteristics.

Up- and Downconversion Luminescence in Ho<sup>3+</sup>,Yb<sup>3+</sup>-Co-Doped Y<sub>2</sub>O<sub>3</sub> Transparent Ceramics Prepared by Spark Plasma Sintering

We employed spark plasma sintering (SPS) in the presence of sintering aids to fabricate highquality Ho3+,Yb3+-co-doped Y2O3 transparent ceramics suitable for use as a laser gain medium, and analyzed their microstructure and optical properties. Ho3+,Yb3+-co-doped Y2O3 transparent ceramics with different contents of Yb3+ were fabricated by SPS and exhibited high transparency in both near-infrared and visible regions. All specimens showed high transparency in both the near-infrared and visible-light regions, and sample microstructure was almost unaffected by the amount of doped Yb3+. The transmission spectra of 1 mol% Yb3+ doped specimens exhibited transmissivities of 73.4 and 81.0% at wavelengths of 700 and 1500 nm, respectively. Relatively high transmissivity was quickly achieved through the addition of a sintering aid (1 mol% La2O3) which accelerated mass transport during sintering. The effect of Yb3+ doping on the upconversion photoluminescence of Y2O3:Ho3+,Yb3+ was examined. Irradiation at 980 nm resulted in strong green photoluminescence (552 nm) and weak red photoluminescence (669 nm). Excitation at 447 and 980 nm resulted in strong green emission (5F4, 5S2 → 5I8) from Ho3+. The effects of Yb3+ content and laser input power on emission intensity and luminescence decay were investigated in detail. Under excitation at 980 nm, the presence of Yb3+ increased emission intensity over the entire range, while the opposite behavior was observed under excitation at 447 nm. (Received May 3, 2019; Accepted July 10, 2019)

Adsorption and Diffusion of Lithium in Doped Molybdenum Disulfide Single-Layer with Metal Substituted Sulfur Atom

Considering the S-vacancy defect in single-layer MoS2, the metal doped including Fe-, Co-, Cu-, Zn-, doped specimens in MoS2 single-layer and their effect of the adsorption and diffusion of Li on the MoS2 single-layer were investigated by Density Functional Theory (DFT). Under Mo-rich condition, the Fe-, Co-, Cu-, Zn-doped specimens by substitution of S atom have smaller formation energy than those under S-rich condition. For doped MoS2 single-layer, lithium donates electron to doped specimens, making the band level of the doped specimens downward into the valence band and the Fermi energy level further upward. The Li ion has positive charge, the ion adsorptive property was enhanced because of strong coulomb interaction. These are confirmed by the large adsorption energies (-1.11 ~ -0.44 eV). The diffusion energy barriers except for the path closest doped specimens by substitution of S atom are ~ 0.25, which are similar to that of pristine one. Above all, the metal doped by substitution of S atom MoS2 single-layer are promising anode materials of LIBs.

Destruction of multiferroicity in Tb2BaNiO5 by Sr-doping and its implication to magnetodielectric coupling

The Haldane spin-chain compound, Tb2BaNiO5, with two antiferromagnetic transitions, one at T1 = 63 K and the other at T2 = 25 K, has been recently shown to be an exotic multiferroic below T2. Here, we report the results of our investigation of Sr doping at the Ba site by magnetization, heat-capacity, magnetodielectric (MDE) and pyrocurrent measurements. An intriguing finding, which we stress, is that the ferroelectricity is lost even for a doping level of ten atomic percent, though magnetic ordering prevails. The doped specimens however retain significant MDE behaviour, but with reduced magnitudes and qualitative changes with respect to the behaviour of the parent compound. This implies that ferroelectric order is also crucial for the anomalously large MDE in the parent compound, in addition to the role of 4f single-ion anisotropy.

Synthesis and low temperature densification of (Zr0.8Sn0.2)TiO4 ceramics with improved dielectric properties

A conventional solid-stated reaction was used to synthesize the (Zr0.8Sn0.2)TiO4 powders with varying pre-sintering temperature parameters. Through evaluating the synthetical properties of sintered ceramics prepared by different calcining methods, R3 route with a soaking time of 1.5 h and cooling rate of 3 °C min−1 was determined as the optimal pre-sintering process. Subsequently, La2O3/CBS additives were added into ZST powders, leading to depression of sintering temperature and additional performance improvements, as long as the additive was supplemented in proper weight percent. Nevertheless, excessive additives deteriorated the microstructures of ZST samples, resulting in the decrease of dielectric properties. In this work, the phase contents, microstructures, sintered densities, dielectric performances, and sintering characteristics of ZST specimens were comprehensively studied. A near-zero τf = − 3.69 ppm °C−1 associated with optimal dielectric performances of er = 40.08, Q×f = 42600 GHz (f = 5.54 GHz) was achieved for doped specimen with 0.25 wt% La2O3 + 0.25 wt% CBS additions sintered at 1280 °C for 4 h.

Experimental analysis of tensile, flexural, and tribological properties of walnut shell powder/polyester composites

Polyester composite specimens with varying wt% of walnut shell powder (WSP) were prepared and characterized for their mechanical and tribological properties. The results of mechanical testing showed that the specific tensile modulus increased with an increase in WSP wt%, whereas the specific flexural modulus slightly decreased at 30 wt%. However, the specific tensile and flexural strength of neat polyester specimen were found to be more than the doped specimens. The specific tensile strength decreased with an increase in WSP wt%, whereas the flexural strength substantially varied with wt%. The tribo-properties were investigated using a wear and friction-monitoring apparatus. It was found from the tribo study that the doped specimens offered higher wear resistance than the neat polyester specimen at all the sliding conditions. The friction coefficient of the doped specimens also remained higher than the neat polyester specimen at most of the sliding conditions. Based on these favorable properties, i.e., increased stiffness, lower specific wear rate, and higher friction coefficient, the WSP can be used as a potential bio-filler in friction composites where such properties are highly desirable.

Optical property evaluation of thoria doped with heavier rare‐earth oxides LnO1.5 (Ln = Er3+, Ho3+, Tm3+, and Yb3+)

AbstractTo address the existing gap in the literature of upconversion studies involving thoria, samples of thoria doped with Ho3+‐Yb3+, Er3+‐Yb3+, and Tm3+‐Yb3+ were synthesized following epoxide gel method and were characterized. Fluorite structure of the doped samples was evident for the calcined samples from the corresponding xerogels as noticed in their powder X‐ray diffraction patterns. The presence of a sharp band near 460 cm−1 in the Raman spectra of all these samples supported the results from diffraction experiments. Intraconfigurational f‐f transitions of Ho3+, Er3+, and Tm3+ were present in the UV‐visible absorbance spectra of these samples. Both normal emission and upconversion emission from these samples have been studied. Emissions in all three basic colors were observed in the upconversion emission spectra. Two‐photon process was found to be responsible for the upconversion in these systems. Decay time measurements for these emissions were analyzed. This synthetic process was further extended to determine the extent of dissolution of heavier lanthanides and found that up to 50 mol% of Ho3+, Er3+ and 60 mol% of Tm3+, Yb3+ could be dissolved retaining fluorite structure. Creation of oxygen vacancies for these heavily doped specimens was quite encouraging and it could be useful as solid electrolytes in fuel cells.

Temperature–stable dielectrics based on Ni–doped Bi2Zn2/3Nb4/3O7 pyrochlore ceramics for low temperature co-fired ceramic

As an admirable candidate of thermostable LTCC materials, Bi2(Zn1-xNix)2/3Nb4/3O7 (0.0 ≤ x ≤ 0.5) ceramics with improved dielectric properties have been prepared via conventional mixed oxide route. Microstructure analysis manifests that the phase transition occurs from monoclinic zirconolite phase (β-BZN) to cubic phase (α-BZN) for Ni doped specimens. The crystal field theory supported the analysis of the initial phase transition processes. From the structure transformation and electrical properties test result, the Ni2+ substituted Zn2+ shows an effective method to restrain the grain growth and improve dielectric constant when sintered at 925 °C. The temperature coefficient of dielectric constant is controlled by phase composition and is found to be −6.4 ppm/°C at the two-phase coexistence region of the doping content x = 0.35. The dielectric properties of ε = 101.2, tanδ = 9.5 × 10−4 are obtained in this component. The features of the Bi2(Zn1-xNix)2/3Nb4/3O7 ceramics make them promising for use in high-frequency applications.

Sintering and electrical behavior of ZrP2O7–CeP2O7 solid solutions Zr1-xCexP2O7; x = 0–0.2 and (Zr0.92Y0.08)1-yCeyP2O7; y = 0–0.1 for application as electrolyte in intermediate temperature fuel cells

ZrP2O7-CeP2O7 solid solutions, Zr1-xCexP2O7; x = 0–0.2 and (Zr0.92Y0.08)1-yCeyP2O7; y = 0–0.1, were prepared by partially replacing Zr4+ with Ce4+ and its effect on the phase composition, sintering behavior, microstructure, and ionic conductivity is analyzed. Ce4+-doped specimens showed improved sintering behavior due to the partial reduction of Ce4+ to Ce3+, as confirmed by X-ray photoelectron spectroscopy (XPS). In unhumidified atmosphere, the electrical conductivity of Zr1-xCexP2O7 increased with increasing cerium content, which can be attributed to the increase in densification and formation of oxygen vacancies due to the partial reduction of Ce4+ to Ce3+. For (Zr0.92Y0.08)1-yCeyP2O7; y = 0–0.1 specimens, the electrical conductivity increased ≥ 4 orders of magnitude during humidification in air (pH2O = 0.12 atm). At 80 °C, specimen (Zr0.92Y0.08)0.9Ce0.1P2O7 (ZYCP10) showed a maximum of 1.72 × 10−2 S cm−1 which decreased sharply at 100 °C. Furthermore, Zr0.92Y0.08P2O7 (ZYP), (Zr0.92Y0.08)0.95Ce0.05P2O7 (ZYCP5), and ZYCP10 specimens humidified at 160 °C showed the maximum conductivity of 1.04 × 10−3, 1.32 × 10−3, and 8.09 × 10−3 S cm−1, respectively, at 190 °C.

The Effects of H2SO4 on the Mechanical Behavior and Microstructural Evolution of Polycrystalline Ice

AbstractThe Earth's large continental ice sheets contain a variety of naturally occurring impurities, both soluble and insoluble. Understanding how these impurities affect the rheology, intrinsic thermodynamic properties, and fate of these ice sheets is not well understood. To investigate the effects that trace amounts of H2SO4 have on the flow and ductility of polycrystalline ice, a series of mechanical tests were conducted at −6, −10, −12.5, and −20°C using laboratory‐prepared specimens of polycrystalline ice doped with 1–15 ppm of H2SO4. Parallel tests were performed on identical but undoped specimens of polycrystalline ice. Mechanical testing included constant‐load tensile creep tests at an initial stress of 0.75 MPa and compression tests at constant displacement rates with initial strain rates ranging from 1 × 10−6 to 1 × 10−4 s−1. It was found that H2SO4‐doped specimens of ice exhibited faster creep rates in tension and significantly lower peak stresses in compression, when compared to the undoped ice. Postmortem microstructural analyses were performed using cross‐polarized light thin section imaging, X‐ray computed microtomography, Raman spectroscopy, and electron backscatter diffraction. These analyses showed that H2SO4‐doped specimens had a larger grain size at strains ≤15%, and an earlier onset of microcracking at lower strain rates than the undoped ice. Strain‐induced grain boundary migration was found to be the predominant mechanism of recrystallization in both doped and undoped specimens. Further, an aqueous phase of H2SO4 was found to exist at the grain boundaries and triple junctions of the doped ice, which is thought to have significantly contributed toward its reduced viscosity.

Effect of Zirconium Doping on Oxidation of Single Crystal β-NiAl

Relatively new optical techniques are utilized to study the oxidation of low-index crystal faces of a zirconium doped single crystal β-NiAl. With these non-destructive techniques residual stress, phase composition and thickness of the scales were determined at various temperatures. The results are compared with the results obtained from an undoped counterpart. Interesting differences in scale stress, thickness and phase composition have been observed. The residual stress evolves rather differently than that on the undoped counterpart. Initial lower stress levels in the doped crystal convert to higher stresses at higher oxidation temperatures. The orientation dependence and a stress anomaly observed with the undoped single crystal β-NiAl are still present on the doped sample. Fluorescence and Raman results indicate a higher concentration of θ-Al2O3 on all crystallographic phases with Zr doping. The oxide scales are also thinner on the Zr doped specimen.

Structural and optical characteristic of chalcone doped ZnO nanoparticles

This work was conducted primarily to study the structural and optical properties of a chalcone doped ZnO nanoparticles. These nanomaterials were fabricated for the first time by means of a facile method. The X-ray diffraction, Scanning electron microscope, FTIR spectroscopy and diffuse reflection spectra have been used for characterization. The doped specimens showed hexagonal wurtzite structure with high purity phase, whereas the morphology of spherical ZnO was slightly distorted after doping. The vibration band of ZnO at 438.57 cm−1 was shifted to the higher wave number of 443.51 and 449.28 cm−1 for the dopant 0.5 and 1.5%, respectively. Loading the chalcone on ZnO has resulted in shifting the absorption edge of ZnO to the visible region and decreased the energy band gap.

Thermal history effect on the nucleation of oxygen precipitates in germanium doped Cz-silicon studied by high-energy X-ray diffraction

The oxygen (O) precipitate growth kinetics from moderate and high germanium (Ge) doped Czochralski-growth silicon (Cz-Si) are in-situ investigated at 1000°C utilizing high-energy X-ray diffraction and analyzed with respect to precipitate density within a diffusion-driven growth model. Distinct different precipitation kinetics are observed for high Ge doped specimens. From the comparison of three thermal treatments, it was found that even for a high Ge concentration the nucleation rate at 800°C is not influenced, however it facilitates larger grown-in precipitates of smaller amount as compared to the precipitates in undoped and moderately Ge doped samples. However, those grown-in O precipitates can be erased either by a direct annealing at 1200°C or 1000°C, but on the other hand stabilized by an annealing step at 800°C, which in this manner asa drift step of grown-in precipitates for the high Ge-doped samples. In comparison additional nuclei are formed at 800°C in the moderate and undoped cases.