Increasing Tb Content Research Articles

Photocatalytic, antibacterial and optoelectronic applications of Terbium doped Zinc oxide nanoparticles prepared via chemical co-precipitation method

This work demonstrates facile synthesis of Tb-doped ZnO nanoparticles and investigates their structural, optical, electrochemical, photocatalytic, and antibacterial performance. XRD patterns of undoped and doped ZnO nanoparticles confirm a hexagonal wurtzite structure. TEM and SAED reveals that the particle size is 14–38 nm. SEM images show that ZnO and Tb-doped ZnO nanoparticles have smooth surfaces, and elemental composition was confirmed by EDX analysis. UV–Visible spectrophotometry studies, reveals that the band gap narrows with increasing Tb concentration. Photoluminescence spectra at room temperature showed a band at 538 nm, indicating zinc vacancies and green emission. Tb-doped ZnO with x = 0.075 exhibited the highest photocatalytic activity for degrading Rose Bengal dye compared to other photocatalysts. The electrochemical behaviour of Catechol (CC), Hydroquinone (HQ), and Bisphenol-A (BPA) at Tb–ZnO/MCPE was studied. The modified electrode process for CC and BPA was adsorption-controlled, and simultaneous recognition of CC, HQ, and BPA was achieved, showing an increase in current. Electro polymerization of poly (Congo red) on Tb–ZnO/MCPE confirmed clean deposition on the surface, enhancing electrocatalytic activity. The antibacterial efficacy was tested using the traditional disc diffusion method, showing effective inactivation of bacterial strains, including pathogens such as S. aureus (G+) and E. coli (G-).

The effect of Tb substitution for Ni on microstructure, martensitic transformation and cyclic stability of elastocaloric effect in Ni–Mn–Sn magnetic shape memory alloys

Cyclic stability of elastocaloric effect is the key factor that restricts the elastocaloric cooling application of Ni–Mn–Sn alloys fabricated by the conventional melting technique. Element doping is an effective way to enhance the performance of materials. In this work, the effect of Tb substitution for Ni on martensitic transformation (MT) temperature, microstructure, mechanical properties and cyclic stability of elastocaloric effect in the Ni43.5–xTbxMn45.5Sn11 (x = 0, 0.6, 1.2 and 1.8) magnetic shape memory alloys has been investigated. MT temperatures increase with increasing x from 0 to 1.2 and then decrease with further increasing x to 1.8. The substitution of Tb for Ni introduces γ phase (Tb-rich second phase in Tb-doping alloys). The volume fraction of γ phase increases with increasing Tb content and thus the mechanical properties and the cyclic stability of elastocaloric effect increase with the increase of Tb content. Among these alloys, Ni42.3Tb1.2Mn45.5Sn11 alloy shows a large adiabatic temperature change of 10.0 K induced by applying the uniaxial stress of 550 MPa. In addition, a constant temperature change of 6.5 K shows no apparent degradation under the compressive stress of 350 MPa during 1000 cycles for this alloy. The excellent elastocaloric properties make this alloy a promising candidate for the room-temperature elastocaloric cooling application. The underlying mechanism of the enhanced cyclability of elastocaloric effect and mechanical properties is also revealed.

Room temperature ferromagnetism in dilute magnetic semiconducting ZnO nanoparticles co-doped with Tb and Fe

Room temperature ferromagnetism with the doping of magnetic ions in the semiconducting host is the fundamental criterion for the potential use of spintronics material. In the present study, pure and (Fe, Tb) co-doped ZnO nanoparticles were well-prepared via the co-precipitation method, and corresponding microstructural, magnetic, and optical properties were investigated. The formation of Wurtzite hexagonal crystal structure of pure and doped ZnO was confirmed by X-ray diffraction (XRD) studies. No secondary phase was detected in all samples. Microstructural analysis reveals the spherical morphology of synthesized particles with the average size in the nanometer range. Fourier transforms infrared spectra show Tb–Zn–O stretching at 550 cm−1. Optical absorption spectra show that the bandgap decreases and the absorption band slightly shift toward the visible region with increasing Tb doping, which may be due to the transfer of charge between the Tb ion 4f level and ZnO valance band. The photoluminescence (PL) spectrum exhibits a strong emission in the visible range, and PL emission intensity decreases with increasing Tb concentration and is anticipated to be due to the low recombination rate of electron–hole pairs. Most importantly, the room temperature ferromagnetism (RTFM) was observed in the doped ZnO nanoparticles, ascribed to the bound magnetic polaron (BMP) mechanism. The optical and magnetic outcome demonstrates that prepared (Fe, Tb) co-doped ZnO based dilute magnetic semiconducting (DMS) material are potential candidates for spintronics applications.

Role of element-specific damping in ultrafast, helicity-independent, all-optical switching dynamics in amorphous (Gd,Tb)Co thin films

Ultrafast control of the magnetization in ps timescales by fs laser pulses offers an attractive avenue for applications such as fast magnetic devices for logic and memory. However, ultrafast helicity-independent all-optical switching (HI-AOS) of the magnetization has thus far only been observed in Gd-based, ferrimagnetic amorphous (\textit{a}-) rare earth-transition metal (\textit{a}-RE-TM) systems, and a comprehensive understanding of the reversal mechanism remains elusive. Here, we report HI-AOS in ferrimagnetic \textit{a}-Gd$_{22-x}$Tb$_x$Co$_{78}$ thin films, from x = 0 to x = 18, and elucidate the role of Gd in HI-AOS in \textit{a}-RE-TM alloys and multilayers. Increasing Tb content results in increasing perpendicular magnetic anisotropy and coercivity, without modifying magnetization density, and slower remagnetization rates and higher critical fluences for switching but still shows picosecond HI-AOS. Simulations of the atomistic spin dynamics based on the two-temperature model reproduce these results qualitatively and predict that the lower damping on the RE sublattice arising from the small spin-orbit coupling of Gd (with $L = 0$) is instrumental for the faster dynamics and lower critical fluences of the Gd-rich alloys. Annealing \textit{a}-Gd$_{10}$Tb$_{12}$Co$_{78}$ leads to slower dynamics which we argue is due to an increase in damping. These simulations strongly indicate that acounting for element-specific damping is crucial in understanding HI-AOS phenomena. The results suggest that engineering the element specific damping of materials can open up new classes of materials that exhibit low-energy, ultrafast HI-AOS.

Electrochemical synthesis, structure characterization and magnetic properties of TbxFe7Co3 (x=0, 0.6, 0.8) nanowires

Highly ordered TbxFe7Co3 (x = 0, 0.6, 0.8) nanowires were synthesized in alumina templates by electrochemical deposition method. Here, the effects of Tb content and annealing treatment on the phase composition, morphology, crystalline structure and magnetic properties were investigated. The as-deposited Tb0Fe7Co3 nanowires comprise Fe7Co3 phase. While after adding Tb, the diffraction peaks slightly shift left, indicating the infiltration of Tb atoms into Fe7Co3 phase. After annealing, Tb0Fe7Co3 nanowires still consist of Fe7Co3 phase with a slight enhancement on coercivity. While the annealed nanowires with Tb doped present a complex phase composition containing Fe3Tb, Fe2Tb, Co3Tb, Co17Tb2, TbFeO3 and Fe2O3 phases distribute in the central portion, and Co0.72Fe0.28 at the nanowire outer walls. The annealed TbxFe7Co3 (x = 0.6, 0.8) nanowires show higher magnetic performance owing to the formation of hard magnetic phases, the interfacial elastic coupling between hard and soft phases and the coherent Fe3Tb/Co3Tb interface which restrain the domain wall motion. To be specific, the coercivity and remanence ratio of TbxFe7Co3 (x = 0.6, 0.8) nanowires significantly enhance with increasing Tb content.

Tailoring the properties of nebulizer spray pyrolysis coated FTO thin films through rare earth element terbium for optoelectronic applications

In optoelectronic device, transparent conducting oxide (TCO) acts as an electrode. In this work the rare earth element terbium (Tb) was doped with FTO by simple and inexpensive nebulizer spray pyrolysis (NSP) technique. Structural, optical end electrical properties were investigated for all the synthesized films. X-Ray diffraction (XRD) analysis confirmed that all the prepared films exhibited polycrystalline nature with tetragonal crystal structure and size of the crystalline reduced with increasing Tb concentration. Raman active doubly degenerate mode (Eg), IR active mode (Eu) and vibration mode (B2g) were found from Raman analysis. Atomic force microscope (AFM) images visualises the granular sized particle and the roughness of the Tb doped films. Elememental analysis spectrum exhibited Sn, O, F and Tb elements for 1.5 wt.% Tb doped thin film. Photoluminacence (PL) analysis revealed that UV, blue and green (visible) emission and UV emission intensity was reduced systamatically for the doped films. From UV–Vis analysis, highest optical transmittace were deduced for 1.5 wt.% Tb doped film. Reflectance, absorbance and band gap also been observed for the prepared films. Refractive index, extinction coefficient and dielectric constant values were decreased with increasing Tb doping concentration. High electrical conductivity and carrier concentration were measured using four probe hall effect system. Figure of merit value for the 1.5 wt.% Tb doped film is 1.5 × 10−3 Ω-1 and therefore the prepared film suits to be an electrode in optoelectronic devices.

Tunable Magnetocaloric Properties of Gd-Based Alloys by Adding Tb and Doping Fe Elements.

In this paper, the magnetocaloric properties of Gd1−xTbx alloys were studied and the optimum composition was determined to be Gd0.73Tb0.27. On the basis of Gd0.73Tb0.27, the influence of different Fe-doping content was discussed and the effect of heat treatment was also investigated. The adiabatic temperature change (ΔTad) obtained by the direct measurement method (under a low magnetic field of 1.2 T) and specific heat capacity calculation method (indirect measurement) was used to characterize the magnetocaloric properties of Gd1−xTbx(x = 0~0.4) and (Gd0.73Tb0.27)1−yFey (y = 0~0.15), and the isothermal magnetic entropy (ΔSM) was also used as a reference parameter for evaluating the magnetocaloric properties of samples together with ΔTad. In Gd1−xTbx alloys, the Curie temperature (Tc) decreased from 293 K (x = 0) to 257 K (x = 0.4) with increasing Tb content, and the Gd0.73Tb0.27 alloy obtained the best adiabatic temperature change, which was ~3.5 K in a magnetic field up to 1.2 T (Tc = 276 K). When the doping content of Fe increased from y = 0 to y = 0.15, the Tc of (Gd0.73Tb0.27)1−yFey (y = 0~0.15) alloys increased significantly from 276 K (y = 0) to 281 K (y = 0.15), and a good magnetocaloric effect was maintained. The annealing of alloys (Gd0.73Tb0.27)1−yFey (y = 0~0.15) at 1073 K for 10 h resulted in an average increase of 0.3 K in the maximum adiabatic temperature change and a slight increase in Tc. This study is of great significance for the study of magnetic refrigeration materials with adjustable Curie temperature in a low magnetic field.

Structural and magnetic properties of FePt-Tb alloy thin films

We have studied structural and magnetic properties of ${(\mathrm{FePt})}_{1\ensuremath{-}x}\mathrm{T}{\mathrm{b}}_{x}$ thin films grown at elevated temperatures on MgO(100) substrates. The incorporation of Tb into the chemically ordered $\mathrm{L}{1}_{0}$ FePt lattice gives rise to considerable changes in the structural and magnetic properties, depending on the Tb content and the deposition temperature. When grown at $770{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$, pronounced $L{1}_{0}$ ordering of the initial FePt phase is present. It vanishes gradually with Tb addition, thereby forming additional crystalline Tb-Pt phases at higher Tb content. These structural changes are accompanied by a strong reduction of the perpendicular magnetic anisotropy with increasing Tb content, finally resulting in a soft magnetic material with in-plane easy-axis magnetization. Extended x-ray absorption fine-structure measurements were performed to examine the possible incorporation of Tb into the FePt lattice. Based on the number of Pt first neighbors, the transformation from the initial tetragonal $L{1}_{0}$ structure to the chemically disordered fcc ($A$1) phase with increasing Tb content could be firmly concluded. In a further sample series, FePt was grown at a lower temperature of 530 \ifmmode^\circ\else\textdegree\fi{}C, which leads to reduced initial $L{1}_{0}$ chemical ordering. Adding Tb results in strong elastic stress in the lattice, eventually causing full amorphization of the film. Interestingly, in this case, a spin-reorientation transition from in-plane to out-of-plane magnetic easy axis is found at low temperatures, which is associated with an anisotropic chemical short-range order present in the amorphous phase. Furthermore, x-ray magnetic circular dichroism studies at the $\mathrm{Fe}\phantom{\rule{0.28em}{0ex}}{L}_{3,2}$ and Tb ${M}_{5,4}$ edges for all samples reveal strong antiferromagnetic coupling between Fe and Tb, resulting in a reduction of the net magnetization of the film.

Effect of Tb-doped Concentration Variation on the Electrical and Dielectric Properties of CaF₂ Nanoparticles.

Calcium fluoride (CaF2) nanoparticles with various terbium (Tb) doping concentrations were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), and alternating current (AC) impedance measurement. The original shape and structure of CaF2 nanoparticles were retained after doping. In all the samples, the dominant charge carriers were electrons, and the F− ion transference number increased with increasing Tb concentration. The defects in the grain region considerably contributed to the electron transportation process. When the Tb concentration was less than 3%, the effect of the ionic radius variation dominated and led to the diffusion of the F− ions and facilitated electron transportation. When the Tb concentration was greater than 3%, the increasing deformation potential scattering dominated, impeding F− ion diffusion and electron transportation. The substitution of Ca2+ by Tb3+ enables the electron and ion hopping in CaF2 nanocrystals, resulting in increased permittivity.

Structural, optical and X-ray attenuation properties of Tb3+:BaxCe1-xF3-x (x = 0.18-0.48) nanospheres synthesized in polyol medium.

Uniform Ba0.18Ce0.82F2.82 nanospheres have been obtained after aging a solution of barium and cerium nitrates and sodium tetrafluoroborate in a mixture of ethylene glycol and water at 120 °C for 20 hours. The diameter of the spheres could be tailored from 65 nm to 80 nm by varying the NaBF4 concentration while maintaining their colloidal stability in aqueous suspension. Increasing the aging temperature led to a phase transformation from hexagonal to cubic symmetry and to a concomitant increase of the Ba/Ce ratio, which reached a value close to the nominal one (50/50) at 240 °C. The same method was successful in obtaining Tb3+-doped nanospheres with homogeneous cation distribution and the same morphological features as the undoped material. An intense green emission was observed after the excitation of the Tb3+-doped samples through the Ce3+-Tb3+ energy transfer (ET) band. The ET efficiency increased with increasing Tb content, the maximum emission being observed for the 10% Tb-doped nanospheres. Aqueous suspensions of the latter sample showed excellent X-ray attenuation values that were superior to those of an iodine-based clinically approved contrast agent. Their fluorescence and X-ray attenuation properties make this material a potential dual bioprobe for luminescence bioimaging and X-ray computed tomography.

Effect of Tb and Al substitution within the rare earth and cobalt sublattices on magnetothermal properties of Dy0.5Ho0.5Co2

The effect of Tb and Al substitution within the rare earth and cobalt sublattices on structural and magnetothermal properties of Dy0.5Ho0.5Co2 has been studied. Multicomponent Laves phase alloys Tbx(Dy0.5Ho0.5)1−xCo2−yAly (x=0, 0.3, 0.4, 0.5; y=0, 0.25) synthesized using high-purity metals have been studied using X-ray diffraction analysis, heat capacity and magnetocaloric measurements. Dy0.5Ho0.5Co2 has a first order phase transition at the Curie temperature TC≈110K. Both Tb and Al substitution leads to increase of the TC. The increasing Tb content leads to the decreases slightly the MCE and all the transitions near the Curie temperature are of the first order. As for the Al-containing compounds, MCE measurements show that the phase transition type changes from the first to the second-order. The advantage of Tbx(Dy0.5Ho0.5)1−xCo1.75Al0.25 as compared with Al-free alloys is ‘table-like’ behavior of MCE.

Influence of Tb on easy magnetization direction and magnetostriction of ferromagnetic Laves phase GdFe2 compounds* *Project supported by the National Basic Research Program of China (Grant No. 2012CB619401).

The crystal structure, magnetization, and spontaneous magnetostriction of ferromagnetic Laves phase GdFe2 compound have been investigated. High resolution synchrotron x-ray diffraction (XRD) analysis shows that GdFe2 has a lower cubic symmetry with easy magnetization direction (EMD) along [100] below Curie temperature T C. The replacement of Gd with a small amount of Tb changes the EMD to [111]. The Curie temperature decreases while the field dependence of the saturation magnetization (M s) measured in temperature range 5–300 K varies with increasing Tb concentration. Coercivity H c increases with increasing Tb concentration and decays exponentially as temperature increases. The anisotropy in GdFe2 is so weak that some of the rare-earth substitution plays an important role in determining the easy direction of magnetization in GdFe2. The calculated magnetostrictive constant λ 100 shows a small value of 37×10−6. This value agrees well with experimental data 30×10−6. Under a relatively small magnetic field, GdFe2 exhibits a V-shaped positive magnetostriction curve. When the field is further increased, the crystal exhibits a negative magnetostriction curve. This phenomenon has been discussed in term of magnetic domain switching. Furthermore, magnetostriction increases with increasing Tb concentration. Our work leads to a simple and unified mesoscopic explanation for magnetostriction in ferromagnets. It may also provide insight for developing novel functional materials.

Oxygen Uptake of Tb–CeO2: Analysis of Ce3+ and Oxygen Vacancies

In response to concerns about the world’s generation of greenhouse gases, there are incentives to develop lower energy alternatives to cryogenic air separation. Oxygen sorbents are one such alternative in which high oxygen uptakes are achieved through engineering materials with a high number of oxygen vacancy defects. For a series of Tb–CeO2 mixed oxides, the oxygen uptake was determined using thermogravimetric analysis (TGA). Electron energy loss spectroscopy (EELS) was used to investigate the relative oxygen vacancy concentration and complement those findings obtained using TGA. Gas switching experiments conducted at 700 °C show that a higher oxygen uptake was obtained when 30% Tb was incorporated into the lattice (76 μmol·g–1) in comparison to when 10% Tb was introduced (21 μmol·g–1). The O IB/IC ratio, indicative of oxygen vacancies, was found to increase with increasing Tb content, and Raman spectroscopy demonstrated that these defects were introduced with the addition of Tb. The increase in oxygen u...

Magneto-structural transition and magnetocaloric effect of melt spinning Ni50Mn29Ga21−xTbx (x = 0-1) ribbons

Ni50Mn29Ga21−xTbx (x=0-1) ribbons with the solid solution of Tb element were synthesized by the melt spinning method. The phase transformation, magnetic properties and magnetocaloric effect were investigated. With the increasing Tb content the martensitic transformation temperatures were gradually increased while the Curie temperature was monotonously decreased. According to the detected phase transition temperatures, a phase diagram was established to describe the dependence of the magneto-structural transition on the Tb content. Three types of magneto-structural transitions were observed. Especially, the martensitic transformation was coincided with the magnetic transition in the single phase alloy with x = 0.1, giving rise to the coupled magneto-structural transition from ferromagnetic martensite to paramagnetic austenite. Sizable magnetic entropy change of 4.31 J/KgK was induced from the coupled magneto-structural transition by the application of magnetic field of 50 kOe at 349.5 K.

Martensitic transformation, shape memory effect and mechanical properties of dual-phase Ni50−xTbxMn30Ga20 (x=0–1) alloys

The addition of rare earth elements (RE) is an effective way to improve the mechanical properties of Ni–Mn–Ga alloys. Unlike previous investigations which were completely focused on the N–Mn–(Ga,RE) alloys, in this work Ni50−xTbxMn30Ga20 (x=0–1) alloys in the form of (Ni,RE)–Mn–Ga were systematically studied with the microstructure, martensitic transformation, shape memory effect and mechanical properties. Dual-phase microstructure containing body-centered tetragonal martensite and Tb-rich hexagonal precipitates were formed. With the increasing Tb content, the volume fraction of the precipitates was also increased. Yet stable martensitic transformation occurring at about 80°C was observed over the whole composition range. Both the transformation temperatures and hysteresis (∼11°C) were quite insensitive to the composition variation. Sizable shape memory effect is obtained in all the polycrytalline alloys. Shape memory effect of 2.68% was detected for the alloy x=1 with large amount of precipitate. With the increasing volume fraction of precipitates both the compressive strength and strain were well increased for x≤0.2 and gradually decreased for 0.2≤x≤1. The transition of fracture mode from intergranular fracture to transgranular fracture and then to interphase fracture was revealed to contribute to the evolution of the mechanical properties.

Optimization on magnetic anisotropy and magnetostriction in TbxHo0.8−xPr0.2(Fe0.8Co0.2)1.93 compounds

The structure, magnetocrystalline anisotropy compensation, magnetic properties, and magnetostriction of TbxHo0.8–xPr0.2(Fe0.8Co0.2)1.93 (0≤x≤0.30) polycrystalline alloys have been investigated. X-ray diffraction (XRD) analysis shows that all the alloys stabilize in the single Laves phase with a MgCu2-type cubic structure. The lattice parameter, Curie temperature and saturation magnetization monotonically increase with increasing Tb content. The easy magnetization direction (EMD) at room temperature is detected rotating from the <100> axis (x≤0.10) to the <111> axis (x≥0.15), accompanied by a rhombohedral distortion with large spontaneous magnetostriction coefficients λ111. The analysis of XRD, EMD and magnetostriction shows that TbxHo0.8–xPr0.2(Fe0.8Co0.2)1.93 is an anisotropy compensation system, and the critical compensation point is realized around x=0.15, which shifts to the Tb-poor side compared with the Pr-free counterpart. An optimized effect on magnetostriction especially at a relatively low field (λS~445ppm, λa~510ppm/3kOe) was obtained in Tb0.15Ho0.65Pr0.2(Fe0.8Co0.2)1.93 compound, which is much larger than that of the Pr-free counterpart Tb0.15Ho0.85(Fe0.8Co0.2)1.93 (λS~300ppm) and the Tb0.15Ho0.85Fe2 (λS~325ppm), due to the 20at% Pr introduction. Low content of heavy rare earth Tb, low anisotropy, high saturation magnetostriction and large low-field magnetostriction are obtained in Tb0.15Ho0.65Pr0.2(Fe0.8Co0.2)1.93 compound, which may make it a promising magnetostrictive material.

Influence of Tb doping on structure and multiferroic properties of BiFeO3 films prepared by pulsed laser deposition

Tb-doped bismuth ferrite (Bi1−xTbxFeO3, 0≤x≤0.15) films were prepared on Pt(111)/Ti/SiO2/Si substrates using a pulsed laser deposition method, so as to modify the multiferroic properties of BiFeO3 films by appropriate Tb doping. The effects of Tb concentration on the crystallographic structure, surface morphology as well as the dielectric, ferroelectric and ferromagnetic properties of the films were investigated. Single-phased Bi1−xTbxFeO3 films were obtained at x=0.05–0.15, and the structural transition from tetragonal or orthorhombic to rhombohedral occurred as increasing Tb concentration, with the decreasing in grain size. The addition of Tb improved the ferromagnetic property of BiFeO3 films although the ferroelectric polarization was slightly degraded, showing obvious magnetic hysteresis loops and typical antiferromagnetic characters. The coexistence of ferroelectric property and ferromagnetic property was realized at room temperature in the Bi1−xTbxFeO3 films by appropriate Tb doping.

Effect of Tb substitution on structural, optical, electrical and magnetic properties of BiFeO3

Tb substituted BiFeO3 [Bi1−xTbxFeO3 (x = 0.05, 0.10, 0.15)] have been synthesized by a low temperature assisted Co-precipitation method. Rietveld-refinement of the X-ray diffraction data reveals a transition from rhombohedral (R3c) to orthorhombic (Pnma) phase, i.e. polar to non-polar phase with Tb substitution. The crystallite sizes of Bi1−xTbxFeO3 (x = 0.05, 0.1 and 0.15) are found to be approximately 30, 21 and 15 nm calculated using Debye–Scherrer equation. From transmission electron microscopy analysis, the particle sizes are found to be between 35–40, 30–35, and 25–30 nm, respectively for Bi1−xTbxFeO3 (x = 0.05, 0.10 and 0.15) samples. UV–Vis diffuse reflectance spectra show a decrease of band gap with increase in Tb concentration. 4A1 and 7E Raman modes have been observed in the range 100–650 cm−1 and two phonon modes centred around 1150–1450 cm−1 have also been observed. The changes in Raman modes such as prominent frequency shift, line broadening and intensity reveals the existence of substitution induced structural changes as supported by the Rietveld refinement. Temperature dependent dielectric measurements on the samples show magnetoelectric coupling in terms of a dielectric anomaly near the Neel temperature (TN). An enhancement of magnetization with increasing Tb concentration in BFO has been observed from room temperature magnetization studies. The leakage current density is found to be reduced with the increase of Tb concentration. Further, P–E hysteresis loop studies show a decrease of remnant polarization (Pr) with the increase in Tb concentration predicting a transition from ferroelectric (polar) to paraelectric (non-polar) phase as inferred from X-ray diffraction analysis.

Enhanced temperature stability in Tb-doped (Ba0.99Ca0.01)(Ti0.98Zr0.02)O3 lead free ceramics

Lead-free (Ba0.99Ca0.01)(Ti0.98Zr0.02)O3 (BCZT)+xmol% Tb (x=0–0.6) ceramics were prepared using a solid-state reaction technique. Phase structure, dielectric constant, ferroelectricity and temperature-dependent piezoelectric coefficient were explored. With an increasing Tb content, the orthorhombic–tetragonal phase transition temperature (TO–T) shifted to lower temperature while its Curie temperature (Tc) remained at 130°C. The temperature stability of piezoelectric coefficient (d33) could be enhanced from 30 to 120°C in Tb-doped BCZT ceramics. A piezoelectric coefficient of d33=542pm/V was obtained at x=0.2 with low temperature-dependent degradation from 30 to 120°C. The results indicated that Tb-doped BCZT ceramics could be a promising candidate for commercial purposes.

Structural, magnetic and magnetostrictive properties of Laves-phase compounds TbxHo0.9−xNd0.1Fe1.93 (0 ≤ x ≤ 0.40)

The structural, magnetic and magnetostrictive properties of TbxHo0.9−xNd0.1Fe1.93 (0 ≤ x ≤ 0.40) alloys have been investigated by means of X-ray diffraction (XRD), a vibrating sample magnetometer and a standard strain technique. Single Laves phase (Tb,Ho,Nd)Fe2 compounds with a cubic MgCu2-type structure have been synthesized at equilibrium conditions with ambient pressure. The lattice parameter of the Laves phase increases linearly with increasing Tb content and obeys the linear Vegard's law. The easy magnetization direction (EMD) at room temperature rotates continuously from <100> for x = 0.10 to <111> for x = 0.25 through an intermediate direction <110> around x = 0.15, subjected to the anisotropy compensation between Tb3+ and Ho3+ ions. The splitting of (440) XRD peak accompanied by the spontaneous magnetostriction-induced rhombohedral distortion is observed for the compounds of x ≥ 0.2, and the spontaneous magnetostriction coefficient λ111 is found to increase with increasing Tb content. The analysis of XRD, EMD, magnetization and magnetostriction shows that the pseudobinary system TbxHo0.9−xNd0.1Fe1.93 is an anisotropy compensation system and the compensation point is realized around x = 0.25. The Nd-containing Tb0.25Ho0.65Nd0.1Fe1.93 Laves-phase compound has good magnetostrictive properties, that is, a large saturation magnetostriction (λS∼585 ppm) and a low magnetocrystalline anisotropy at room temperature, which may make it technological interest for magnetostriction applications.