We have prepared LaCrO3 (LCO) and 10% Ir doped LCO samples by the solid state reaction method and studied the electrical modulus and the other dielectric properties of the samples by means of the impedance spectroscopy in the −100 °C to 100 °C range, with steps of 20 °C. It has been clearly observed that the dielectric properties change due to Ir doping. The absolute dielectric constant value of Ir doped LCO has decreased and this reduction was attributed to decreasing Cr6+ ions which may play a vital role in space charge polarization and charge hopping. A plateau region appeared in the temperature-dependent real electrical modulus M′ versus f curves of the pure LCO sample while almost no plateau region is visible in the Ir doped LCO sample. The temperature-dependent imaginary modulus M′′ versus f curves has two peaks at each temperature; one of the peaks is at low frequency and the other at the high frequency region, which shifts through higher frequency region with increasing temperature. This originates from free charge accumulation at the interface with the increase of the temperature. Furthermore, it has been seen that the Ir doped LCO sample has higher impedance and resistance values than the undoped LCO sample at the same frequency and temperature. This phenomenon was attributed to doped Ir ions behaving like a donor in LCO because LCO is a p-type compound. Moreover, the activation energy values of 0.224 eV and 0.208 eV for LCO and of 0.161 eV and 0.265 eV for the Ir doped LCO have been obtained from the slopes of the ρdc vs. (kT)−1 curves, respectively. Also the activation energies were calculated from the slopes of the fmax vs. (kT)−1 curves and the obtained results from low frequency region were in good agreement with ρdc vs. (kT)−1 ones.

/pdf/the-electrical-modulus-and-other-dielectric-properties-by-3xpx12paxb.pdf

The electrical modulus and other dielectric properties by the impedance spectroscopy of LaCrO3 and LaCr0.90Ir0.10O3 perovskites

Investigation of energy transfer and concentration quenching of Dy3+ luminescence in Gd(BO2)3 by means of fluorescence dynamics

Tthe present work studied the cationic substitution of Y3+ by Bi3+ on the crystal structure of orthorhombic YFeO3 and its effect over magnetic, dielectric and electric properties of multiferroic yttrium orthoferrite. Stoichiometric mixtures of Y2O3, Fe2O3 and Bi2O3 were mixed and milled for 5 h using a ball to powder weight ratio of 10:1 by high-energy ball milling. The obtained powders were pressed at 1500 MPa and sintered at 700 °C for 2 h. The test samples were characterized at room temperature by X-ray diffraction (XRD), vibrating sample magnetometer (VSM), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and impedance spectroscopy (IS). The X-ray diffraction patterns disclosed a maximum solubility of 30 % mol. of Bi3+ into the orthorhombic YFeO3. For higher concentrations, a transformation from orthorhombic to garnet structure was produced, obtaining partially Y3Fe5O12 phase. The substitution of Bi3+ in Y3+ sites promoted a distortion into the orthorhombic structure and modified Fe-O-Fe angles and octahedral tilt. In addition, it promoted a ferromagnetic (FM) order, which was attributed to both the crystal distortion and Dzyaloshinskii-Moriya interaction. For doped samples, an increase in real permittivity values was observed, and reduced with the increase of frequency. This in good agreement with the Maxwell-Wagner effect.

/pdf/enhanced-multiferroic-properties-of-yfeo3-by-doping-with-bi3-1at2vl5dl7.pdf

Enhanced Multiferroic Properties of YFeO3 by Doping with Bi3

Magnetic and dielectric properties of orthoferrites La1−x PrxFeO3 (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5)

Electrical characterization of Ir doped rare-earth orthoferrite YbFeO3

Dielectric relaxation of Y1−xRxFeO3 (R = Dy, Er, x = 0, 0.5)

The antiferromagnetic G-type magnetic ordering in Y2AlCrO6 (YAC) has been investigated by electronic band structure calculations. The material is synthesised by a sol–gel technique and the electronic structure calculations are initiated by the experimental lattice parameters, obtained from the Rietveld refinement of the X-ray diffraction data. The Rietveld refinement shows that the room-temperature crystal structure of YAC is monoclinic with the space group P21/n, and contains an ordered array of alternating AlO6 and CrO6 octahedra tilted along the three pseudocubic axes according to the Glazer notation a−a−b+. The Raman spectrum of the sample is observed for P21/n symmetry. The field cooled and zero field cooled measurements of the sample are performed at a magnetic field of 100 Oe in the temperature range from 5 to 300 K. The temperature dependent magnetization shows the anti-ferromagnetic ordering of Cr ions in YAC. The calculated magnetic moment is well matched with the experimental magnetic moment and suggests the 3+ oxidation state of Cr with the canted alignment of its spin. The octahedral co-ordination of Cr3+ ions in YAC is confirmed from the photoluminescence spectrum. The band gap obtained from the diffuse reflectance measurements shows the semiconducting nature of the material. To observe the effect of grains, grain-boundaries and electrodes in the conduction process, the dielectric relaxation of YAC has been investigated using alternating current impedance spectroscopy in the frequency range from 50 Hz to 5 MHz as a function of temperature. An electrical equivalent circuit consisting of the resistance and the constant phase element is used to explain the impedance data. The observed results are used to discuss the effect of substitution of Cr by Al in the parent compound YCrO3.

Electronic structure and transport properties of antiferromagnetic double perovskite Y2AlCrO6

The complex perovskite oxide yttrium erbium iron oxide, Y1/2Er1/2FeO3 is synthesized by the solid-state reaction technique. The Rietveld refinement of X-ray diffraction pattern at room temperature (30°C) shows the orthorhombic Pnma phase with lattice parameters a = 5.582 A, b = 7.593 A, c = 5.267 A. Impedance spectroscopy study of Y1/2Er1/2FeO3 has been performed in the frequency range from 50 Hz to 1 MHz and in the temperature range from 303 K to 503 K. The frequency dependence of real and imaginary parts of dielectric permittivity is analyzed using modified Cole-Cole equation. The complex impedance plane plots of the sample shows that both grain and grain-boundary effects are present in the relaxation (conduction) process. The frequency dependent conductivity spectrum is found to follow the power law.

Indrani Das

Papers

Dielectric relaxation of Y1−xRxFeO3 (R = Dy, Er, x = 0, 0.5)

Electronic structure and transport properties of antiferromagnetic double perovskite Y2AlCrO6

Structural and dielectric properties of Y1/2Er1/2FeO3