Standard Solid-state Reaction Method Research Articles

Magnetic and optical properties of Ti doped ZnO prepared by solid state reaction method

The substitution of transition metal ions on zinc oxide as host lattice may lead to some interesting behavioural changes in magnetic and optical properties. The present work discusses the effect of Ti dopant in zinc oxide Zn1−xTixO (x=0.02 and 0.03) on the optical and magnetic properties. For that, Ti doped zinc-oxide (ZnO) was prepared by standard solid state reaction method in a high temperature furnace. The magnetic properties were analysed using vibrating sample magnetometry. The morphology of the samples was studied by SEM micrographs. The effect of the dopant on the semiconducting nature of the host ZnO was investigated by UV–vis studies.

Structural, optical, and magnetic properties of Fe doped In2O3 powders

Iron doped indium oxide dilute magnetic semiconductor (In1−xFex)2O3 (x=0.00, 0.03, 0.05, and 0.07) powders were synthesized by standard solid state reaction method followed by vacuum annealing. The effect of Fe concentration on structural, optical, and magnetic properties of the (In1−xFex)2O3 powders have been systematically studied. X-ray diffraction patterns confirmed the polycrystalline cubic structure of all the samples. An optical band gap increases from 3.12eV to 3.16eV while Fe concentration varying from 0.03 to 0.07. Magnetic studies reveal that virgin/undoped In2O3 is diamagnetic. However, all the Fe-doped In2O3 samples are ferromagnetic. The saturation magnetization (Ms) of ferromagnetic (In1−xFex)2O3 (x=0.03, 0.05, and 0.07) samples increases from 11.56memu/g to 148.64memu/g with x=0.03–0.07. The observed ferromagnetism in these samples was attributed to magnetic nature of the dopant (Fe) as well as defects created in the samples during vacuum annealing.

Effect of Annealing Temperature and Boron Addition on Magnetic Properties of Hexaferrites Synthesized by Standard Ceramic Method

The barium and strontium hexaferrites (BaM and SrM) were successfully prepared by the standard solid-state reaction method. To inhibit crystal growth, 1 wt % B2O3 was added into the initial mixture. The structural and magnetic properties of pure hexaferrites were compared with the samples prepared with boron addition. Powders were annealed at temperatures between 800 and 1200 ∘C. The crystal structure, morphology, and magnetic properties of hexaferrites were investigated with X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM). BaM was synthesized at temperatures as low as 800 ∘C with boron addition having saturation magnetization of ∼50 emu/g and coercivity of ∼3 kOe. At the same temperature, pure sample has very low magnetization about 1.3 emu/g. Moreover, at higher sintering temperatures, boron-containing samples have higher magnetization values compared to pure BaM. The optimal Fe/Ba ratio was determined as 10.5 for boron-containing samples, while it is 11.5 for the pure one. The coercivity started to decrease at 1100 ∘C indicating that single to multi-domain transition occurs. The saturation magnetization values are nearly equal in pure- and boron-containing SrM samples in the whole temperature range. However, maximal coercivities occurred at different temperatures for boron-containing and the pure samples as 1000 and 1100 ∘C, respectively. Magnetic interactions deduced from the Stoner–Wohlfarth model using the isothermal magnetization and demagnetization measurements showed that boron addition suppresses the destructive (demagnetizing-like) interactions among domains in both SrM and BaM samples, and thus, stabilizes the remanence.

Effects of A1 site occupation on dielectric and ferroelectric properties of Sr4CaRTi3Nb7O30 (R = Ce, Eu) tungsten bronze ceramics

Sr4CaRTi3Nb7O30 (R = Ce, Eu) tungsten bronze ceramics are prepared by a standard solid state reaction method. The effects of A1 site occupation on the dielectric and ferroelectric properties of Sr4CaRTi3Nb7O30 (R = Ce, Eu) tetragonal tungsten bronzes are investigated. The Sr4CaCeTi3Nb7O30 shows a normal transition behavior due to the closer size ion occupation in A1 sites, which could suppress the distortion of B2 octahedra effectively. Sr4CaEuTi3Nb7O30 ceramic exhibits two dielectric anomalies, which might be related to the fact that the large radius difference between Ca2+ and Eu3+ could lead to the uneven distribution of Ca2+ and Eu3+ in A1 sites and form two slightly different kinds of compositions with different transition temperatures in the structure. Our results indicate that the ionic radius difference in A1 sites plays an important role in determining the dielectric and ferroelectric natures of the filled tungsten bronze ceramics. Polarization—electric field (P—E) curves are evaluated at room temperature and both of them show hysteresis loops. Sr4CaCeTi3Nb7O30 shows a fat hysteresis loop, indicating the long-range ferroelectric order in the ceramic. The current density—electric field (J—E) curves are measured at room temperature with a largest leakage current density of ∼ 10−6 A/cm2, indicating that their leakage currents are rather low.

Photoluminescent properties of Sr2CeO4 : Eu3+ and Sr2CeO4 : Eu2+ phosphors suitable for near ultraviolet excitation

Powder phosphors of 1 mol% Eu3+- and Eu2+-doped strontium cerium oxide (Sr2CeO4) were synthesized by standard solid-state reaction method. Eu3+- and Eu2+-doped Sr2CeO4 phosphors fired at 1100 °C for 2 h were analysed by X-ray diffraction (XRD) and photoluminescence (PL) techniques. The XRD patterns confirm that the obtained phosphors are a single phase of Sr2CeO4 composed of orthorhombic structure. Room temperature PL excitation spectrum of air-heated Sr2CeO4 : Eu phosphor has exhibited bands at 260, 280 and 350 nm. Whereas the excitation spectrum of Sr2CeO4 : Eu phosphor heated under reducing (carbon) atmosphere exhibited single broadband range from 260 to 390 nm. The (PL) emission peaks of both the phosphors at 467 (blue), 537 (green) and 616 nm (red) generate white light under 260, 280 and 350 nm excitation wavelengths. The Commission International de l’Eclairage (CIE) colour coordinates conforms that these phosphors emitting white light. The results reveal that these phosphors are multifunctional phosphors which emit white light under these excitations that they could be used as white components for display and lamp devices and as well as possible good light-conversion phosphor LEDs under near-ultraviolet (nUV) chip.

Study of magnetic and magnetocaloric properties of La0.6Pr0.1Ba0.3MnO3 and La0.6Pr0.1Ba0.3Mn0.9Fe0.1O3 perovskite-type manganese oxides

The compositional dependence of the magnetic and magnetocaloric properties of La0.6Pr0.1Ba0.3MnO3 (LPBMO) and La0.6Pr0.1Ba0.3Mn0.9Fe0.1O3 (LPBMFO) were investigated. Polycrystalline samples were prepared by the standard solid-state reaction method. Temperature-dependent magnetization measurements and Arrott analysis reveal second-order ferromagnetic transitions in both samples with Curie temperature increasing with doping iron from 94 K for LPBMO to 277 K for LPBMFO. Magnetic entropy change $$ | {\Delta S_{\text{M}} } | $$ was calculated by applying the thermodynamic Maxwell equation to a series of isothermal field-dependent magnetization curves. However, the analysis of the magnetocaloric effect (MCE) using Landau theory of phase transition shows that the contributions to the free energy from the presence of ferromagnetic clusters are strongly influencing the MCE by coupling with the order parameter around the Curie temperature.

Microstructure and dielectric properties of (Nb + In) co-doped rutile TiO2 ceramics

The (Nb + In) co-doped TiO2 ceramics recently attracted considerable attention due to their colossal dielectric permittivity (CP) (∼100,000) and low dielectric loss (∼0.05). In this research, the 0.5 mol. % In-only, 0.5 mol. % Nb-only, and 0.5–7 mol. % (Nb + In) co-doped TiO2 ceramics were synthesized by standard conventional solid-state reaction method. Microstructure studies showed that all samples were in pure rutile phase. The Nb and In ions were homogeneously distributed in the grain and grain boundary. Impedance spectroscopy and I-V behavior analysis demonstrated that the ceramics may compose of semiconducting grains and insulating grain boundaries. The high conductivity of grain was associated with the reduction of Ti4+ ions to Ti3+ ions, while the migration of oxygen vacancy may account for the conductivity of grain boundary. The effects of annealing treatment and bias filed on electrical properties were investigated for co-doped TiO2 ceramics, where the electric behaviors of samples were found to be susceptible to the annealing treatment and bias field. The internal-barrier-layer-capacitance mechanism was used to explain the CP phenomenon, the effect of annealing treatment and nonlinear I-V behavior for co-doped rutile TiO2 ceramics. Compared with CaCu3Ti4O12 ceramics, the high activation energy of co-doped rutile TiO2 (3.05 eV for grain boundary) was thought to be responsible for the low dielectric loss.

Physical properties of the new multiferroic perovskite-like material [formula omitted

We report the study of the structural, magnetic and electrical properties of the multiferroic material with perovskite structure HoMn1−xFexO3 (x=0; 0.1 and 0.2) synthesized by the standard solid state reaction method. Structural analysis by X-ray diffraction (XRD) experiments shows the coexistence between two phases with the same chemical formula and with polyhedral distortions (MnO3), a phase with hexagonal symmetry (P63cm # 185) which is characteristic of the non-doped material HoMnO3 and other perovskite phase with orthorhombic symmetry (Pbnm # 62). Rietveld refinements of the experimental patterns show that the weight percentage of each phase (hexagonal or orthorhombic symmetry) depends on the degree of substitution of Fe in the Mn crystallographic sites. Measurements of polarization as a function of applied voltage at room temperature confirm a ferroelectric character for non-doped material with relative permittivity of 215.1. These measurements show that the ferroelectric behavior is deteriorated by the introduction of Fe, since in the configuration with x=0.1 (HoMn0.9Fe0.1O3) we can see ferroelectric loops with dielectric losses to small values of applied voltage and finally in the configuration with x=0.2 (HoMn0.8Fe0.2O3) the behavior is totally resistive at room temperature. Curves of magnetization as a function of temperature were carried out between 300K and 860K show an antiferromagnetic behavior in the three configurations of the HoMn1−xFexO3 material.

The effect of Ca-substitution in La-site on the magnetic properties of La2CoMnO6

Double perovskite La2-xCaxCoMnO6 (x = 0, 0.1, 0.2, 0.5) ceramics samples were synthesized by the standard solid-state reaction method. The crystal structures have been confirmed to be monoclinic perovskite structure with space group of P21/n at room temperature by the powder x-ray diffraction (Cu-Kα). The grains of the samples are relatively dense and distribute in random directions from the scanning electron microscope patterns. Holes are doped into La2CoMnO6 with the substitution of the Ca2+ ions in La-site, and further lead to the valences of Mn ions and Co ions transforming from Mn4+ and Co2+ to Mn3+ and Co3+, respectively. Ferromagnetic coupling of Mn4+-O2–-Co2+ and antiferromagnetic coupling of Mn3+-O2–-Co3+ are coexistent in La2-xCaxCoMnO6 system, which correspond to two transitions existed in field-cooling magnetization versus temperature curves. Curie temperature of La2-xCaxCoMnO6 system decreases with the increasing of Ca-substitution amount. The coexistence of different magnetic phases leads to the exchange bias effect.

Effects of La Doping on the Structural and Dielectric Properties of Barium Titanate Ceramics

Polycrystalline samples of Ba1-xLaxTiO3 (x = 0.0, 0.002, 0.004) were prepared by a standard high-temperature solid-state reaction method. XRD studies confirmed the formation of a polycrystalline compound with a tetragonal crystal structure. SEM images suggested the presence of a polycrystalline microstructure with certain degree of porosity, and the grains appeared to be distributed inhomogeneously throughout the pallet samples. Dielectric studies indicated a ferroelectric–paraelectric phase transition with a clear shift in the Curie temperature (Tc) of BaTiO3 towards a lower temperature upon doping. The brick-layer model was used to study the potential barrier and the structure of the grain-boundary region of the Ba9.998La0.002TiO3 and Ba9.996La0.004TiO3 ceramics. These ceramics exhibited good density and a homogeneous distribution of the grains. The thickness of the grain-boundary region was calculated to be approximately 200 nm.

Magnetic properties of Cu3.9Fe3.4V6O24 with a lyonsite structure

Magnetic properties of the lyonsite-type phase, Cu3.9Fe3.4V6O24, that has been synthesized by a standard solid-state reaction method, were investigated by dc magnetization and electron paramagnetic resonance (EPR) techniques. Complex magnetic behavior and transition to the antiferromagnetic phase at liquid helium temperature have been revealed by measurements of dc susceptibility in ZFC and FC modes in the 2–300 K temperature range as well as static magnetization in magnetic fields up to 70 kOe. Strong antiferromagnetic interactions in clusters or chains of magnetic ions even at high temperatures has been deduced from the obtained value of the effective magnetic moment that was significantly smaller than expected for nominal valences of iron and copper ions. The presence of antiferromagnetic iron dimers in the high-temperature range, critical slowing down of spin fluctuations on approaching Neel temperature and the existence of magnetically isolated iron ions in the antiferromagnetic phase has been suggested from the temperature dependence of EPR parameters (g-factor, linewidth, integrated intensity) obtained by fitting the experimental spectrum with Lorentzian lineshape.

Structure and microwave dielectric characteristics of (Sr1−xCax)Nd2Al2O7 ceramics

(Sr1−xCax)Nd2Al2O7 (x = 0, 0.1, 0.3, 0.5) ceramics were synthesized by a standard solid state reaction method. Their microwave dielectric properties were investigated together with the structural evolution. X-ray diffraction analysis indicated that Ruddlesden–Popper solid solutions with n = 2 were obtained for all the compositions investigated here. Ca-substitution significantly improved the densification behavior which was associated with the variation of εr. More importantly, with increasing the content of Ca, τf value was generally improved towards near-zero, and the significantly improved Qf value was obtained at x = 0.5. The stacking fault and distorted lattice fringe in the ceramics were confirmed by TEM observation, and these defects were deeply concerned with the microwave dielectric loss. The best combination of microwave dielectric characteristics was achieved for the composition of x = 0.5: εr = 21.1, Qf = 68,200 GHz and τf = −0.5 ppm/°C.

Effect of (Ta/Nb) co-doping on the magnetoresistivity and flux pinning energy of the BPSCCO superconductors

In the present work, the effect of co-doping of Ta and Nb with nominal composition of (BiPb)2TaxSr2Ca3Cu4−yNbyO12+δ where x = 0.1 and y = 0.0, 0.025, 0.05, 0.075, and 0.1 were investigated. The samples were prepared by using the well-known conventional standard solid-state reaction method. The magnetoresistance measurements were studied for different values of the applied magnetic field. The activation energies, irreversibility fields (H irr ), upper critical fields (H c2 ) and coherence lengths at 0 K (ζ(0)) were calculated from the resistivity versus temperature (ρ-T) curves, under DC magnetic fields up to 6 T. The thermally activated flux flow (TAFF) model has been applied in order to calculate the flux pinning energies. The results have shown that the upper critical magnetic field, H c2 (0), and the flux pinning energies vary from ~113 to 74 T and ~384 to 101 meV at 0 T, with the Nb-content, respectively.

Structural and electrical properties of (x)Mn0.45Ni0.05Zn0.50Fe2O4 + (1 − x)BaZr0.52Ti0.48O3 multiferroic materials

Multiferroic (x)Mn0.45Ni0.05Zn0.50Fe2O4 + (1 − x)BaZr0.52Ti0.48O3 materials (where x varies from 0.0 to 0.8 in steps of 0.20) were prepared by the standard solid state reaction method. X-ray diffraction patterns verify the development of tetragonal perovskite structure for ferroelectric and cubic spinel structure for ferrite phase. The frequency and temperature dependent electrical parameters have been investigated to understand the conduction mechanism in these multiferroic materials. The grain effect contributes to the conduction mechanism for the sample containing 0–60% ferrite and both the grain and grain boundary effect contribute to the conduction mechanism for the composite containing 80% ferrite at high temperature. The ac conductivity increases with increasing frequency for the sample x = 0. This is due to the small polaron hopping. For the sample containing 20% ferrite, the frequency independent dc conductivity is observed at low temperature and dominates over a wide frequency range at high temperature region for the sample containing higher percentage of ferrite. The frequency independent dc conductivity is shifted to the frequency dependent ac conductivity, indicating the beginning of the conductivity relaxation phenomenon. This is attributed to the translation of long range polaron hopping to the small range charge carriers. The temperature dependence conductivity indicates that the impurities present in these multiferroic materials are almost minimized and polaron hopping type of conduction mechanism is valid.

Characterization of ceramics materials mixed with Co3O4

We have performed the preparation, structural, electrical and mechanical characterizations of ceramic materials composed of kaolinite Al2(Si2O5)(OH)4 and alumina (Al2O3) mixed with different concentrations of cobalt oxide (Co3O4). Ceramic samples were prepared from a base concentration of alumina 30% and kaolinite 70%, mixed with various concentrations of cobalt oxide in steps of 4% up to a value of 20%. The samples were sintered by the standard solid-state reaction method at a temperature of 1350 °C. In all samples with cobalt was found the presence of mullite. It was determined that alumina and cristobalite decreased when the cobalt concentration was increased due to the formation of the cobalt spinel. In order to determine the crystal structure of the samples, crystallographic analysis from X-ray diffraction experiments and also the semi-quantitative phase analysis were performed. Results were compared with theoretical parameters through the PowderCell 2.4 software. By increasing the concentration of cobalt oxide was found a significant increase in the resistance of materials to friction wear and a small decrease on the mean value of the dielectric constant. Through flexion measurements is observed the increases of the elasticity modulus by about 45% for the sample with 4% of cobalt oxide when compared with the samples without cobalt.

Noncentrosymmetric versus Centrosymmetric: Influence of the Na+ Substitution on Structural Transition and Second-Harmonic Generation Property

A series of K3–xNaxB6O10Br (0.5 ≤ x ≤ 1.2) polycrystalline samples have been synthesized by the standard solid-state reaction method. Four stoichiometric crystals K3–xNaxB6O10Br (x = 0.13, 0.67, 1.30, 2.20) have been successfully grown from the high-temperature solution, and the crystal structures were determined by single-crystal X-ray diffraction. Interestingly, the Na+ concentration plays a profound role to influence the crystal structure. Up to about 23% (x = 0.7) K+ ions can be substituted by Na+ ions with the same noncentrosymmetric (NCS) crystal structure of K3B6O10Br (space group R3m) being retained, while a higher Na concentration would lead to it crystallizing in the centrosymmetric (CS) space group Pnma. Meanwhile, the second-harmonic generation (SHG) response of K3–xNaxB6O10Br (x ≤ 0.7) is about 2.8 times that of KDP, while the SHG response decreases sharply when x > 0.7 (the SHG response is zero at x = 1.3). After careful structural analysis, we believe that the different Br-M (M = K/Na, K, o...

Synthesis, Electrical And Thermal Properties Of Bi4V2-xCuxO11 (x=0.0 And 0.02) Ceramics

Polycrystalline ceramic samples of pure and Cu +2 doped Bi4V2-xCuxO11(x=0.0 and 0.02) have been synthesized by standard solid state reaction method using high purity oxides. The dielectric constant and dielectric loss and hence ac conductivity as a function of frequency and temperature have been measured. The dielectric studies indicate that the material is highly lossy and hence its ac conductivity increases with the increase of temperature. The dc conductivity of material has been measured as a function of temperature from room temperature to 653 K and its activation energy was calculated using the relation σ = σo exp (- Ea/kT). The dc conductivity increases with the substitution of Cu on the vanadium site. The Modulated Differential Scanning Calorimetry (MDSC) has been used to investigate the effect of substitution on the phase transition of the compounds. The results are discussed in detail.

Effect of different element doping on the structure and magnetic properties of composite crystal Sr14(Cu1−xMx)24O41 (M=Zn, Ni, Co)

The Zn2+, Ni2+ and Co3+ doped Sr14(Cu1−xMx)24O41 composite crystals were synthesized by a standard solid state reaction method. The temperature dependence of magnetic properties was measured for every sample. The Curie coefficient, Weiss temperature, number of dimers in CuO2 chain per formula unit (f.u.) and dimer coupling constant are obtained by fitting the temperature dependence of the magnetic susceptibility. Meantime, selected area electron diffraction patterns (EDPs) show that the diffraction spots corresponding to the CuO2 chain substructure are extended to streaks along a⁎ and b⁎ directions for all the samples, while the diffraction spots produced merely by the Cu2O3 ladder substructure are still very sharp. This means that the periodicities of chains in a⁎ and b⁎ directions are partially destroyed upon doping of Zn, Ni and Co due to that the initial phase of each chain becomes a random variable. Considering the effect of different ions substitution for Cu on the magnetic susceptibility, it is found that the degree of initial phase disorder is related to the order degree of magnetic sequence in CuO2 chain. For the un-doped sample, the decoupling of dimers is weak, the magnetic sequence is slightly destroyed, and the streaks in EDP are also very weak, which implies the degree of initial phase disorder in CuO2 chain is very low. When Zn2+ and Ni2+ ions are doped, the number of dimers per f.u. decreases, and the intensity of diffraction streaks increases. Furthermore, when the high spin magnetic ions Co3+ are doped, the number of holes in Sr14(Cu1−xCox)24O41 decreases, the magnetic sequence is destroyed very seriously, and the spots in EDP are extended to streaks almost completely. The phenomenon that the diffraction spots of CuO2 chain extend to streaks in EDP appears as evidence that the magnetic sequence in the CuO2 chain is destroyed by doping of Zn, Ni, Co.

Substitutional effects on structural and magnetotransport properties of La0.85−xSmxK0.15MnO3 (x = 0.05, 0.1 and 0.15)

A series of polycrystalline La0.85−xSmxK0.15MnO3 (x=0.05, 0.1 and 0.15) have been synthesized by standard solid state reaction method to study effects of substituting La3+ by Sm3+ ion on the structural, electrical and magnetic properties. The Rietveld refinement of X-ray diffraction data revealed that mixed valence manganites crystallize in rhombohedral structure (space group R3¯C, no. 167). Raman spectra at room temperature reveal gradual change in phonon modes on increased doping. The temperature dependent electrical resistivity is measured by a standard four-probe method between 5 and 300K. The temperature dependent electrical resistivity exhibits metal–insulator transition at temperature TMI and metallic state (T<TMI) signifies importance of electron–electron, electron–phonon and electron–spin fluctuation scattering process. The peak resistivity ρm increases rapidly with Sm and TMI shifts to a lower temperature. The high temperature (T>TMI) conductivity data signifies polaronic nature. Application of magnetic field suppresses resistivity in entire temperature range. Low temperatures resistivity infers a field-dependent minimum and is due to electron–electron interaction and Kondo effects of mixed valence manganites. The ferro to paramagnetic transition temperature (TC) decreases with decreasing ionic radius as well as one-electron bandwidth of the A-site cation.

Study on the electrical properties of Co–Ti double substituted Bi4V2O11

In the present work Bi2V0.9Co0.1−xTixO5.35+X; 0.02 ⩽ x ⩽ 0.08 was synthesized through standard solid state reaction method. X-ray diffraction and differential thermal analysis has been observed for various compositions and it was found that the tetragonal γ-phase stabilized with γ′ ↔ γ phase transition for all the compositions. The ionic conductivity and dielectric permittivity of BICOTIVOX have been investigated by using AC impedance spectroscopy. The values of two components of complex impedance and the relaxation time of oxide ion movement through the grain interior and grain boundary decrease with increase temperature. The thermal dependence of total ionic conductivity revealed maximum (2.64 × 10−4 S cm−1) for x = 0.04 at 300 °C.