Substitution Of Rare-earth Ions Research Articles

Effect of rare earth ion substitution on phase decomposition of apatite structure.

The paper describes an investigation of phase decomposition of apatite lattice doped with rare earth ions (cerium, samarium, and holmium) at temperatures ranging from 25 to 1200 ºC. The rare-earth ion-doped apatite minerals were synthesized using sol-gel method. In situ high-temperature powder X-ray diffraction (XRD) was used to observe phase changes and the lattice parameters were analyzed to ascertain the crystallographic transformations. The expansion coefficient of the compounds was determined, and it was found that the c-axis was the most expandable due to relatively weak chemical bonds along the c-crystallographic axis. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to examine the decomposition properties of the materials. Due to rare earth ion doping, the produced materials had slightly variable decomposition behaviour. The cerium and samarium ions were present in multiple oxidation states (Ce3+, Ce4+, Sm3+, Sm2+), whereas only Ho3+ ions were observed. Rare earth ion substitution affects tri-calcium phosphate proportion during decomposition by regulating concentrations of vacancies. X-ray photoelectron spectroscopy (XPS) analysis indicated that cerium and samarium ion-doped apatite yielded only 25% tricalcium phosphate during decomposition. This finding advances our understanding of apatite structures, with implications for various high-temperature processes like calcination, sintering, hydrothermal processing, and plasma spraying.

Giant enhancement of photoluminescence in Mn4+-activated Ba2CaWO6 phosphors via heterovalent doping with rare-earth ions

Currently, Mn4+-activated phosphors have attracted extensive attention for their versatile applications in general lighting, display and plant cultivation. Owing to 3d3 electronic configuration of Mn4+ ion, modifying its local coordination environment emerges as a potent method to tailor its luminescence behavior. Herein, a heterovalent substitution strategy is reported to greatly enhance the photoluminescence (PL) of Ba2CaWO6:Mn4+. The effects of the substitution of rare-earth ions (Ln3+ = Lu3+, Y3+, Gd3+, La3+) for Ca2+ ions on the PL properties of the phosphor are studied in detail. The PL spectral change of Mn4+ induced by Ln3+ substitution is clarified in terms of the local structure of [WO6] octahedron and the valence state of Mn. By selection of Ln3+ ions and optimization of Ln3+ doping concentration, the emission intensity of Ba2Ca0.85Gd0.15WO6:0.25Mn4+ phosphor reaches up to 46.3 times as that of Ba2CaWO6:0.25Mn4+. Besides, the Ba2Ca0.85Gd0.15WO6:0.25Mn4+ phosphor exhibits an internal quantum yield of 56.9 % and a thermal stability of 72.6 %@423 K. Finally, Ba2Ca0.85Ln0.15WO6:Mn4+ based phosphor conversion LED devices are demonstrated, which can be potentially employed for indoor plant lighting.

Microstructure, ferromagnetic resonance, and electrical analysis of Ho-substituted Li-Ni nanoparticles

The substitution of rare earth ions is a novel approach to vary the dynamic magnetic properties of soft ferrites to such an extent that its electrical properties and ferromagnetic resonance (FMR) response can be set over a broad frequency range. In this work, a complete transmission electron microscopy (TEM), scanning electron microscopy (SEM), ferromagnetic resonance spectroscopy (FMR), X-ray photoelectron spectroscopy (XPS), and current-voltage (I-V) analysis of holmium (Ho) substituted lithium-nickel soft ferrites with composition Li1.2Ni0.4Fe2−xHoxO4 (x = 0, 0.03, 0.06, 0.09, 0.12, and 0.15) is carried out. TEM analysis reveals a spherical shape distribution of nanoparticles with a particle size of ∼ 50 nm. FMR study is carried out to check the role of Ho addition on magnetic energy losses, FMR line position, and shape. The shift in FMR line shape is mainly attributed to the anisotropy contribution, relaxation processes, and ferromagnetic interactions between the magnetic nanoparticles. XPS experiments confirm the presence of all compositional elements along their valence states. The Ho substitution increased the electrical resistivity, whereas the damping of A-B exchange interactions resulted in a decline of Curie temperature (Tc), which is required for high-frequency power applications.

Effects of Nonmagnetic Zn2+ Ion and RE Ion Substitution on the Magnetic Properties of Functional Nanomaterials Co1-yZnyRExFe2-xO4 (RE = La, Sm, Gd) by Sol-Gel.

Magnetic Functional Nanomaterials Co1-yZnyRExFe2-xO4 (RE (rare-earth) = La,Sm,Gd) were prepared using the sol-gel combustion method. XRD characterization confirms that the ferrite samples we synthesized are single-phase cubic structures. The variation in the average crystalline size and lattice parameter is related to RE ion doping. The Mössbauer spectra of CoRExFe2-xO4 are two sets of magnetic six-wire peaks that indicate the ferrimagnetic behavior of the sample. The calcination temperature greatly influences the absorption area of Mössbauer for CoFe2O4, indicating that the calcination temperature affects the iron ion content at the octahedral B and tetrahedral A sites. Additionally, scanning electron microscopy measurements of the substituted specimens reveal that the ferrite powders are nanoparticles. With an increase in RE ions, the coercivity increases, and the saturation magnetization changes obviously. The XRD characterization of Co0.7Zn0.3LaxFe2-xO4 shows that the main crystalline phase of the sample is the cubic spinel structure phase, and there are fewer secondary crystalline phases. The lattice parameter tends to decrease with the substitution of La3+ ions. The average grain size decreased significantly with the increase in La content. From ferrimagnetic state transition to relaxation behavior, the hyperfine magnetic field decreases in La concentration by room temperature Mössbauer spectra. With the substitution of La3+ ions, both the saturation magnetization and coercivity of the samples were reduced, and the coercivity of all samples was lower.

Large Difference in Nonlinear Optical Activity of Rare Earth Ion Substitution of Bi3+ in A3TeBO9 (A = Bi, La, Pr, Nd, Sm-Dy).

A series of oxides with high rare earth contents, RE3TeBO9 (RE = La, Pr, Nd, Sm-Dy), were synthesized, and they all crystallize in the noncentrosymmetric space group P63 resembling that of a previously reported Bi3TeBO9 (J. Am. Chem. Soc. 2016, 138, 14190-14193), which showed a very strong second harmonic generation (SHG) signal believed to come from all three structural units [BO3], [TeO6], and [BiO6]. Surprisingly, compared with the isostructural compound Bi3TeBO9, both theoretical calculations and powder SHG tests show that RE3TeBO9 has an abnormally small SHG effect (0.2 × KDP). Based on the group theory analysis, the possible reasons are attributed to the misalignments and lack of distortions of the [BO3], [TeO6], and [REO8] groups in the unit cell. The 21 symmetric operation (a subset operation of the 63-screw axis) of the [TeO6], [BO3], and [REO8] groups leads to complete cancellation of their contributions to the xy directions, while the absence of lone pair electrons in RE3+ and Te6+ results in small distortion in the c axis, hence small contributions to the SHG coefficients dijk involving the z axis. Diffuse reflectance spectra of RE3TeBO9 (RE = La, Pr, Nd, Sm-Dy) show typical absorption of different RE3+, and the similarity of their infrared spectra is due to the same crystal structure and same structural units of the [TeO6] and [BO3] groups. The strong fluorescence intensities of Eu3TeBO9 and Tb3TeBO9 show the characteristic emissions of Eu3+ and Tb3+, which may serve as luminescence materials with proper doping.

Effect of rare earth ions (RE = La3+, Sm3+, Nd3+, and Gd3+) substitution on structural, magnetic properties, and dc electrical resistivity of Co0.5Ni0.5Fe2O4 ferrite

Effect of rare earth ions (RE = La3+, Sm3+, Nd3+, and Gd3+) substitution on structural, magnetic properties, and dc electrical resistivity of Co0.5Ni0.5Fe2O4 ferrite

Comparison of rare earths doping (neodymium and samarium) on structural and magnetic properties of Ni–Zn–Bi nanoferrites

Excellent magnetic properties in ferrites are required for high-frequency applications and for wastewater treatment. Thus, the present study shows the comparison of magnetic and structural properties of Nd and Sm substituted Ni–Zn–Bi ferrites with the series Ni0.5Zn0.5Bi0.04NdxFe1.96–xO4 (with step size 0.002) and Ni0.5Zn0.5Bi0.04SmxFe1.96–xO4 (with step size 0.02) prepared using citrate precursor method. The impact of the substitution of rare earth ions (Nd and Sm) on magnetic properties of the synthesized samples is observed using a vibrating sample magnetometer (VSM). The saturation magnetization values enhance considerably from 52 to 58 emu/g for Nd3+ ions and 39 to 57 emu/g for Sm3+ ions, thus, making these materials magnetically hard. Further, the higher value of coercivity is also observed ranging from 133 to 167 Oe for Nd3+ ions and 81 to 155 Oe for Sm3+ ions. The shape of hysteresis loops indicates a super paramagnetic and ferromagnetic behavior in the obtained samples. The squareness ratio value is <0.5, suggesting the uniaxial anisotropy of particles and hence, these ferrites are suitable for microwave-absorbing and in permanent magnetic materials. The X-ray diffraction (XRD) pattern shows the formation of pure cubic crystallites, where, lattice parameters range from 0.840 to 0.839 nm and from 0.838 to 0.839 nm for Nd3+ and Sm3+ ions substitution, respectively. The crystallite size ranges between 28.63 to 29.89 nm and 18.33 to 26.23 nm, for substitution of Nd3+ and Sm3+ ions, respectively. Field emission scanning electron microscopy (FESEM) shows the formation of homogeneous grains, whereas, energy dispersive spectrometer (EDS) counts describe the purity of the samples. The Sm concentration x = 0.10 has the maximum surface area with value of 42.6 m2/g which proves to be having good data storage application due to high surface area. The zero-field cooled (ZFC) and field cooled (FC) data show that Nd-doped Ni–Zn–Bi nanoferrites show superparamagnetic behaviour in the room temperature range which makes them suitable for practical applications.

A novel reddish-orange-emitting phosphor Ca3Gd7(PO4)(SiO4)5O2: Sm3+ for white light-emitting diodes

Phosphor is the decisive material in white light-emitting diodes (WLED), affecting light quality. Silica phosphate has good stability, low cost and environmentally friendly features, so it has great application potential. In this paper, a self-activated reddish-orange phosphor Ca3Gd7(PO4)(SiO4)5O2: xSm3+ was prepared by the high-temperature solid-phase method. The phase purity of the sample was verified by X-ray diffraction (XRD). The Rietveld refinement method was used to resolve further the sample structure and the location of the substitution of rare earth ions. The photoluminescence properties were studied in detail using fluorescence spectra, temperature-dependent emission spectra and other characterization methods. The electron transition and energy transfer processes of Gd3+ in Ca3Gd7(PO4)(SiO4)5O2 were analyzed. The fluorescence decay curve of the sample was obtained, which belongs to the double exponential curve, and the decay lifetime depending on the Sm3+ doping concentration was calculated. Furthermore, a WLED device was assembled, and warm white light was obtained, with a spectrum showing characteristic red emission, proving to complement the missing red component of commercial WLEDs. These results indicate that Ca3Gd7(PO4)(SiO4)5O2: xSm3+ phosphor has great potential for application.

A comparative study on structural, magnetic and optical properties of rare earth ions substituted Bi1−x R x FeO3 (R: Ce3+, Sm3+ and Dy3+) nanoparticles

Abstract A comparative study on the manifestation of rare earth ions substitution induced alteration in structure, magnetic and optical properties of BiFeO3 nanoparticles was done. Sol-gel technique was employed to synthesize Bi1−x R x FeO3 (x = 0.05 and 0.10; R: Ce3+, Sm3+ and Dy3+) nanoparticles. X-ray diffraction patterns and Raman spectra analysis confirmed substitution driven structural phase transformation from distorted rhombohedral structure to orthorhombic structure for x = 0.10 samples. The enhanced magnetic properties with weak ferromagnetic behaviour were observed with increasing concentration of rare earth ions in BiFeO3 nanoparticles. The improved magnetic characteristics are attributed to many factors such as the uncompensated surface spins in nanoparticles, breaking of spin cycloid with R 3+ ions substitution and super exchange interaction between R 3+ and Fe3+ ions. The maximum magnetization values of 1.77 emu g−1, 1.87 emu g−1 and 5.5 emu g−1 were observed for x = 0.10 samples with Ce3+, Sm3+ and Dy3+ substitution, respectively. The magnetization increased with increasing difference in ionic radii of host Bi3+ (1.17 Å) ion and dopant Ce3+ (1.14 Å), Sm3+ (1.08 Å) and Dy3+ (1.03 Å) ions. UV–Visible diffuse reflectance spectra showed a sharp absorption in visible region and energy band gap values variation in the range 2.2 eV–2.33 eV.

Possible structural quantum criticality tuned by rare-earth ion substitution in infinite-layer nickelates

Materials with competing phases that have similar ground state energies often exhibit a complex phase diagram. Cuprates are a paradigmatic example of such a system that show competition between charge, magnetic, and superconducting orders. The infinite-layer nickelates have recently been revealed to feature similar characteristics. In this paper, I show that these nickelates are additionally near a structural quantum critical point by mapping the energetics of their structural instabilities using first-principles calculations. I first confirm previous results that show a phonon instability in the $P4/mmm$ phase leading to the $I4/mcm$ structure for $R\mathrm{Ni}{\mathrm{O}}_{2}$ with $R$ = Sm--Lu. I then study the non-spin-polarized phonon dispersions of the $I4/mcm$ phase and find that they exhibit rare-earth size-dependent instabilities at the $X$ and $M$ points for materials with $R$ = Eu--Lu. Group-theoretical analysis was used to enumerate all the isotropy subgroups due to these instabilities, and the distorted structures corresponding to their order parameters were generated using the eigenvectors of the unstable phonons. These structures were then fully relaxed by minimizing both the atomic forces and lattice stresses. I was able to stabilize only five out of the twelve possible distortions. The $Pbcn$ isotropy subgroup with the ${M}_{5}^{+}(a,a)$ order parameter shows noticeable energy gain relative to other distortions for the compounds with late rare-earth ions. However, the order parameter of the lowest-energy phase switches first to ${X}_{2}^{\ensuremath{-}}(0,a)+{M}_{5}^{+}(b,0)$ and then to ${X}_{2}^{\ensuremath{-}}(0,a)$ as the size of the rare-earth ion is progressively increased. Additionally, several distorted structures lie close in energy for the early members of this series. These features of the structural energetics persist even when antiferromagnetism is allowed. Such a competition between different order parameters that can be tuned by rare-earth ion substitution suggests that any structural transition that could arise from the phonon instabilities present in these materials can be suppressed to 0 K.

Fortified relaxor ferroelectricity of rare earth substituted 4-layered BaBi3.9RE0.1Ti4O15 (RE = La, Pr, Nd, and Sm) Aurivillius compounds

In this report, the effect of rare-earth (RE3+) ion substitution on structural, microstructural, and electrical properties in barium bismuth titanate (BaBi4Ti4O15) (BBTO) Aurivillius ceramics has been investigated. The Rietveld refinements on X-ray diffraction (XRD) patterns confirm that all the samples have an orthorhombic crystal system with A21am space group. Meanwhile, temperature dependent synchrotron XRD patterns reveal that the existence of dual phase in higher temperature region. The randomly oriented plate-like grains are experimentally strived to confirm the distinctive feature of bismuth layered Aurivillius ceramics. The broad band dielectric spectroscopic investigation signifies a shifting of ferroelectric phase transition (Tm) towards low temperature region with a decrease of the RE3+-ionic radii in BBTO ceramics. The origin of diffuse ferroelectric phase transitions followed by stabilization of the relaxor ferroelectric nature at high frequency region is explained using suitable standard models. The temperature dependent ac and dc conductivity results indicate the presence of double ionized oxygen vacancies in BBTO ceramics, whereas the dominance of single ionized oxygen vacancies is observed in RE-substituted BBTO ceramics. The room temperature polarization vs. electric field (P–E) hysteresis loops are shown to be well-shaped symmetric for BBTO ceramics, whereas slim asymmetric ferroelectric characteristics developed at RE-substituted BBTO ceramics.

Microwave absorption properties of rare earth (RE) ions doped Mn–Ni–Zn nanoferrites (RE = Dy, Sm, Ce, Er) to shield electromagnetic interference (EMI) in X-band frequency

Sol-gel auto combustion technique has been adopted to prepare RE doped Mn–Ni–Zn ferrite systems following the stoichiometry Mn0.1Ni0.7Zn0.2RE0.5Fe1.5O4 (RE = Dy, Ce, Sm and Er). The XRD patterns confirm the cubic spinel phase with the Fd3m space group and the lattice parameter and crystallite size were found to be in the range of 8.3874–8.4066 Å and 28.6–33.2 nm. The M − H data indicates the soft magnetic behaviour of present ferrite systems. The substitution of rare-earth ions in the spinel structure influences the superexchange interaction and in turn, affects the magnetic behaviour of present ferrite systems. The highest value of saturation magnetization equal to 41.2 emu/g was observed for the sample with a composition of Mn0.1Ni0.7Zn0.2Ce0.5Fe1.5O4. For all the ferrite systems studied here the real part (ε′) of complex permittivity is increasing with an increase in frequency while oscillatory nature can be found in the imaginary part (ε″). The value of ε′ found in the range of 5.421–5.856 at 8.2 GHz and it is 5.538–6.066 at 12.4 GHz. The value of ε″ is in the range of 0.092–0.104 at 8.2 GHz while it is in between 0.042 and 0.105 at 12.4 GHz. A wavy nature can be seen in the real part (μ′) of complex permeability whereas the imaginary part (μ″) is decreasing for all compositions with the increase in frequency, but shows a weak resonance peak between 9 and 10 GHz. The value of μ′ is in the range of 0.869–0.958 at 8.2 GHz and it is 0.903–0.925 at 12.4 GHz. The value of μ″ fall in between 0.269 and 0.334 at 8.2 GHz and it is in the range of 0.059–0.068 at 12.4 GHz. The shielding studies for EMI revealed that the present systems are working as microwave absorbers. The total effective shielding for all ferrite systems is in the range of 33.31–36.09 dB 8.2 GHz while it is in between 32.74 and 34.98 dB at 12.4 GHz. Under the investigation of shielding performance, it is observed that all the RE doped Mn–Ni–Zn ferrites systems studied here can effectively suppress the electromagnetic interference in X-band frequency. The ferrite system with composition Mn0.1Ni0.7Zn0.2Ce0.5Fe1.5O4 has shown a potential microwave absorber in X-band frequency.

Study of cation distribution in La3+ and Eu3+ substituted cobalt ferrite and its effect on magnetic properties

The rare-earth metal ion substitution in the spinel ferrites significantly alters its cation distribution, leading to changes in their structural and magnetic properties. Herein, we have studied the structural and magnetic behaviour of rare-earth (RE = La3+ and Eu3+) substituted cobalt ferrites (CoFe2-xRExO4; x = 0.03 per f.u.) synthesized using the conventional solid-state route. Both the samples possess a cubic structure with Fd3¯m space group. Substituting La3+ and Eu3+ creates a structural distortion and compresses the lattice parameter and unit cell volume of CoFe2O4 due to their large ionic radii compared to Fe3+. Raman spectroscopy pattern confirms the cubic structure of the samples; however, the variation in the intensity of A1g modes suggests the occurrence of cation redistributions. The inversion parameter (i) value calculated using the Mössbauer spectroscopy is 0.78, suggesting that pristine CoFe2O4 has a mixed spinel state. Furthermore, the ‘i’ value decreased to 0.69 and 0.66, respectively, upon incorporating La3+ and Eu3+ cations, confirming the occurrence of cation redistributions in the samples. Besides, the decreased probability of super-exchange interaction and reduction in the magnetic behaviour are caused by the migration of Co2+ cation from the octahedral-[B] site to the tetrahedral-(A) site and partial replacement of Fe3+ ion by RE3+ elements.

Symmetry evolution and modulation of multiferroic characteristics in Bi1−xLaxFeO3 ceramics

The substitution of rare-earth ions has been recognized as an effective way to modify the multiferroic properties, especially to realize the electric field-controlled magnetism in BiFeO3 ceramics, in which the symmetry modulation of R3c/Pna21 and the unlocked ferromagnetism through breaking the cycloidal spin structure are the key issues. Here, the enhancement of ferroelectric polarization and weak ferromagnetism are investigated in Bi1−xLaxFeO3 ceramics together with the magnetoelectric coupling coefficient αME with the development of the Pna21 phase. The expected electric field-controlled magnetism is achieved at the phase boundary through the electric field-induced transition of Pna21/R3c, where the variation of magnetization reaches 34.18 emu/mol (58.95%) at x = 0.18 after poling.

Solution-combustion synthesized highly luminescent CaTiO3:Gd2O3:Eu3+ perovskite nanophosphors for WLED applications

A series of Ca (1- x - y ) TiO 3 : x Gd 3+ , y Eu 3+ perovskite nanophosphors were synthesized by the solution combustion employing metal-citrate complexation method. The luminescence enhancement of seven times and the color purity of 97.4% were observed when 5 mol% of Gd 3+ ions were substituted in the Ca 0.93 TiO 3 :0.07Eu 3+ phosphor. The occupancy of Gd 3+ and Eu 3+ ions at Ca 2+ sites were detected by Rietveld refinements and XPS spectroscopy. The characteristic binding energy peaks of Europium and Gadolinium ions evidenced their 3+ oxidation state. Raman shifts observed for these phosphors affirmed the phase purity and the appearance of localized vibrational modes at 803 cm −1 signifying the substitution of rare earth ions in the crystal. The TEM analysis confirmed a high degree of crystallinity. The single exponential nature of the luminescence decay curves vindicated the substitution of the activator ions at a unique site. The thermal activation energy of 0.31 eV obtained for Ca 0.88 Gd 0.05 TiO 3 :0.07Eu 3+ suggested an appreciable stability against thermal quenching due to the cross-over process. The color parameters, luminescence lifetime, Judd–Ofelt parameters and radiative properties have been fairly discussed. • Ca (1-x-y) TiO 3 :xGd 3+ , yEu 3+ nanophosphors were synthesized by solution combustion synthesis. • The optimum doping of Gd 3+ ions in Ca 0.93 TiO 3 :0.07Eu 3+ enhanced luminescence seven times. • The increase in the local asymmetry was denoted by color purity of 97.4% and enhancement of Judd–Ofelt parameter, Ω 2 . • The occupancy of dopants at Ca 2+ sites were detected by Rietveld refinements and XPS spectroscopy. • Raman shifts observed for these phosphors affirmed the phase purity.

Evaluation of the microstructure, optical properties and hopping conduction mechanism of rare earth doped Ba0.85Ca0.12RE0.03Ti0.90Zr0.04Nb0.042O3 ceramics (RE = Ce3+ and Pr3+).

The current research work examines the impact of Rare Earth (RE3+) ion substitution on the structural, optical and conduction properties of a Ba0.85Ca0.12RE0.03Ti0.90Zr0.04Nb0.042O3 (BCRETZN) (RE = Ce, Pr) ceramic compound produced via a solid-state route. The Rietveld method of the X-ray data revealed a tetragonal (P4mm) structure at room temperature for our ceramic compound. The morphology of the compound was explored using Scanning Electron Microscopy (SEM) as well as optical response and conduction behavior. The photoluminescence properties revealed that the BCPrTZN sample results in green and red photoemissions under laser excitation at 450 nm at RT. Furthermore, for the BCCeTZN sample, the photoluminescence data demonstrated that strong violet emission bands were acquired, at RT upon an excitation at 350 nm. The electrical conduction process was verified via the correlated barrier Hopping method. The scaling behavior suggests that the electrical conduction mechanism is independent of temperature. The existence of Ce3+ and Pr3+ ions in these materials could have important technological potential in new multifunctional devices.

Enhancing the magnetization, dielectric loss and photocatalytic activity of Co–Cu ferrite nanoparticles via the substitution of rare earth ions

This study reports the impact of lanthanum (La) substituted Co–Cu ferrite nanoparticles on the rhodamine (RhB) dye disposal. Moreover, a complete investigation for the structural, magnetic and optical properties for Co0.5Cu0.5LaxFe2-xO4 (CCL) nanoferrites was executed. These nanocrystals were synthesized via a combustion approach with a peculiar lattice parameter behavior; which discussed through three hypotheses. The scanning transmission electron microscope - energy dispersive X-ray analysis (STEM-EDX) micrographs of some selective samples confirm the nanocrystalline nature with presence of all constituents’ chemical elements CCL nanoferrites. The saturation magnetization of CCL nanoferrites was tuned with La3+ ions substitution. Contrary to the expected results, anisotropy constant introduced a decrement behavior with La/Fe substitution process. The microwave frequency (ωM) values for all CCL nanoparticles are in the range 11.87–9.46 GHz. The band gap has a peculiar behavior; a red shift and followed by a blue one. Through photodegradation testing, we explicate the RhB degradation mechanisms over our CCL nanoferrites. The nanoferrite Co0.5Cu0.5La0.15Fe1.85O4 has a moderate saturation magnetization, highest coercivity, and lowest loss, which is a suitable candidate for data recording applications, furthermore can be utilized as a photocatalyst for RhB effluents removal with degradation efficiency 94.50% at 180 min solar radiation.

Synthesis, structural and thermal expansion investigation of La, Ce and Eu substituted Bi4(SiO4)3

A series of selected rare earth ions substituted bismuth silicates of the chemical formula Bi 4-x RE x (SiO 4 ) 3 (RE = La, Ce and Eu: X = 0.1, 0.2, 0.3) was synthesized by the solution method. Rietveld refinement study revealed that the compounds Bi 4 (SiO 4 ) 3 , Bi 3.9 La 0.1 (SiO 4 ) 3 , Bi 3.8 La 0.2 (SiO 4 ) 3 , Bi 3.7 La 0.3 (SiO 4 ) 3 , Bi 3.9 Ce 0.1 (SiO 4 ) 3 and Bi 3.9 Eu 0.1 (SiO 4 ) 3 were crystallized in cubic structure with I - 43d space group. Scanning electron microscopic images indicated that the larger and rod shaped particles were transformed into smaller and agglomerated ones when the rare earth ions were substituted for Bi ion in the octahedral site. UV–visible diffuse reflectance spectra displayed a shift in absorption edge upon rare earth ion substitution due to the overlapping of s-p transition band with Ln 3+ -O 2- charge transfer band. Bulk thermal expansion of the pure phases was tested using push rod dilatometer. The average coefficients of thermal expansion for Bi 4 (SiO 4 ) 3 , Bi 3.9 La 0.1 (SiO 4 ) 3 , Bi 3.9 Ce 0.1 (SiO 4 ) 3 and Bi 3.9 Eu 0.1 (SiO 4 ) 3 were found to be 5.19 x 10 −6 / ° C, 5.59 x 10 −6 / ° C, 7.10 x 10 −6 / ° C and 7.94 x 10 −6 / ° C, respectively. The effect of rare earth ionic substitution in thermal expansion behavior was investigated. • New rare earth substituted eulytite type ceramics were prepared by solution method. • Rietveld refinement study proved the formation of cubic phases with I - 43d space group. • The effect of rare earth ionic substitution was observed from SEM and UV-DRS. • Average thermal expansion coefficients the compounds were found to be in the range of 5.19–7.94 x 10 −6 /°C. • Heating and cooling cycles of thermal expansion showed different amounts of hysteresis.

Influence of rare earth ions (Sm3+, Dy3+) substitution on magnetic and microwave performance of magnesium ferrite

The nano-crystalline rare earth (Sm3+, Dy3+) substituted MgFe2O4 with composition Mg[(Sm)0.6(Dy)0.4]xFe2-xO4 [x varies from 0.0 to 0.3 in steps of 0.05] have been prepared by chemical combustion route. X-ray diffraction analysis confirmed the formation of the spinel cubic phase as a major phase along with the perovskite ortho-ferrite phase as a minor phase in all the samples except MgFe2O4. The room temperature magnetic properties of these samples have been investigated. It has been observed that with an increase in substitution of rare-earth ions (Sm3+, Dy3+), for iron in MgFe2O4, initial permeability increases, attain peak value for the composition with x = 0.15, and decreases for higher substitution concentrations. The microwave absorption performance of the Mg[(Sm)0.6(Dy)0.4]xFe2-xO4 systems have been investigated. The reflection coefficients are found to be higher as compared to MgFe2O4 whereas Voltage Standing Wave Ratio (VSWR) found to be lower. Overall investigations indicate Mg[(Sm)0.6(Dy)0.4]0.15Fe1.85O4 is a promising candidate for microwave device fabrication.

Chemical pressure exerted by rare earth substitution in BiFeO3: Effect on crystal symmetry, band structure and magnetism

Single phase BiFeO3 (BFO) is difficult to synthesize due to the volatile nature of Bi and the formation of impurity phases which restrict its use in commercial applications. Presence of free charge carriers in the system due to the formation of oxygen vacancies leads to an increase in the leakage current and suppresses intrinsic ferroelectric response of the system. In this paper, we present a detailed study of the structural phase transformation triggered by the substitution of rare-earth (RE) ions at A-site of BFO. We report that the chemical pressure induced by the substitutional ions stabilizes lower symmetry polymorphs. A detailed phase diagram showing connection between chemical pressure, ionic radii mismatch, dopant concentration and rare ions is also extracted on the basis of the structural analysis. Change in peak position and intensity of Raman vibrational modes and transformation of structure from rhombohedral to orthorhombic phase are identified to be a function of the concentration of RE ions substituted at the A-site. Five electronic transitions, two d-d and three charge transfer (CT) transitions, are observed in optical measurement within the spectral range of 1–5 eV. Shifts in d-d and CT transitions as a function of substitution are also observed. Dependence of the direct band gap on the concentration of substituent ion is also studied. Presence of spin spiral structure results in net cancellation of magnetic moments in BFO and, as a result, antiferromagnetic hysteresis loop is observed. Substitution of RE ions at A-sites induces chemical pressure which affects Fe-O-Fe bond angle and results in the destruction of spiral spin structure. Consequently, weak ferromagnetism is observed beyond certain concentration of RE in BFO.