Dielectric properties and electrical response of yttrium-doped Bi2/3Cu3Ti4O12 ceramics

(Y[Formula: see text]Bi[Formula: see text]Cu3Ti4O[Formula: see text] ([Formula: see text] 0.00–0.30) ceramics were successfully prepared via the conventional solid-state method. X-ray powder diffraction confirmed the lattice constant gradually decreases with increasing Y[Formula: see text] content. SEM images displayed Y[Formula: see text] substitution for Bi[Formula: see text] gave rise to the large abnormal grains, and the size of abnormal grains became larger with the increase of Y[Formula: see text] substitution. (Y[Formula: see text]Bi[Formula: see text]Cu3Ti4O[Formula: see text] ceramics presented the relatively high dielectric constant of 7400 with the dielectric loss of 0.055 when [Formula: see text] 0.20. The analysis of complex impedance suggested the grains are semiconductive and the grain boundaries are insulating. For pure Bi[Formula: see text]Cu3Ti4O[Formula: see text] ceramics, the appearance of additional low-frequency peaks in electrical modulus indicated the grain boundaries are heterogeneous. The investigation of modulus peaks fitting with Arrhenius formula implied that the low-frequency permittivity for all (Y[Formula: see text]Bi[Formula: see text]Cu3Ti4O[Formula: see text] ceramics was ascribed to the Maxwell–Wagner relaxation at grain boundaries. In addition, a set of clear dielectric peaks above 200[Formula: see text]C associated with Maxwell–Wagner relaxation can be found for all (Y[Formula: see text]Bi[Formula: see text]Cu3Ti4O[Formula: see text] ceramics in the temperature dependence of dielectric constant. This set of clear dielectric peaks showed a tendency to shift to higher temperatures with the increase of Y[Formula: see text] substitution. Meanwhile, a tiny dielectric anomaly at room temperature was found in Y-doped Bi[Formula: see text]Cu3Ti4O[Formula: see text] ceramics.

Structural, optical and dielectric properties of tellurium-based double perovskite Sr2Ni1−xZnxTeO6

In this paper, Sr2Ni1−xZnxTeO6 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) double perovskite compounds were synthesised by the conventional solid-state method, and the structural, optical and dielectric properties were investigated.

Dependence of the Ni0.4Zn0.6Fe2O4 spinel ferrite on frequency and temperature using impedance spectroscopy tool

Ni0.4Zn0.6Fe2O4 ferrites were prepared by the conventional solid-state method. The X-ray study allowed the identification of a single orthorhombic phase. The conductivity of the prepared sample was measured at different frequencies in the temperature range 340 K to 600 K. The obtained results are discussed in terms of charge carriers hopping. We showed that the dielectric permittivity is high at different temperatures and various frequencies. The impedance plane findings present semicircle arcs at various temperatures and an electrical equivalent circuit was determined. In addition, the obtained two relaxation times were established as a function of temperature.

Preparation and Dielectric Properties of K1/2Na1/2NbO3 Ceramics Obtained from Mechanically Activated Powders

Alkaline based materials have been considered as a replacement for environmentally harmful Pb(Zr,Ti)O3 (PZT) electro-ceramics. In this paper, the K1/2Na1/2NbO3 (KNN) ceramics were prepared in a three stage process: first Nb2O5, Na2CO3, and K2CO3 were milled in a high energy mill (shaker type) for different periods, between 25 h and 100 h, consecutively a solid state reaction was carried out at 550 °C. Finally, the uniaxially pressed samples were sintered at 1000 °C. The reaction temperature is lower for mechanically activated powders than in the case of the conventional solid-state method. The ceramic samples, prepared from the mechanically activated powders, were investigated by dielectric spectroscopy. The influence of the duration of the mechanical activation on the properties of the ceramic materials, e.g., ceramic microstructures, phase transition temperatures, character of the temperature dependences of dielectric permittivity, are discussed.

Structure, electric and dielectric properties of PbFe1/3Ti1/3W1/3O3 single perovskite compound

A conventional solid-state method was used to prepare Pb(Fe1/3Ti1/3W1/3)O3 single perovskite material. The sample sintered at 900?C was studied by XRD and after Rietveld refinement the orthorhombic structure with Pbam space group was confirmed. The FTIR frequency bands corresponding to Pb-O, Ti-O, O-lattice, W- O-W and Fe-O stretching vibrations together with the XRD data also confirmed that Fe2+ and W6+ ions are incorporated in the structure and most probably substituted Ti4+ ions at the B site of the perovskite ABO3 structure. The average grain size of the perovskite ceramics, estimated from SEM micrograph, was 1 to 2 ?m. Variation of dielectric properties and AC conductivity with frequency and temperature revealed that the material had semiconducting nature and negative temperature coefficient of resistance (NTCR). The Nyquist plots were modelled with an equivalent circuit consisted of parallel capacitance, resistance and constant phase element corresponding to the grains (bulk) and grain boundaries. It was observed that grain resistance (Rb) of the sample decreases with the rise of temperature, which supports the NTCR behaviour. The semi-circular arcs of the Nyquist and Cole-Cole plots confirm the semiconducting nature of the sample.

Systematic investigation of Eu3+ activated Na2Ln4(MoO4)7 [Ln = La, Gd and Y] narrow band red emitting phosphors for hybrid white LEDs and plant growth

A sequence of Eu3+ activated Na2Ln4(MoO4)7 [Ln = La, Gd and Y] red phosphors has been synthesized using a conventional solid-state method.

Structural, Dielectric and Electrical Properties of Fe Doped La0.7Ba0.3MnO3Solid Solutions for Cathode Materials

The solid solutions of (La0.7Ba0.3)(FexMn1-x )O3 where x = 0.1 - 0.5 ceramics were synthesized by conventional solid-state method. The structural analysis was done by X-Ray diffraction technique and the results have revealed that all the samples were crystallized into a single phase. The surface morphology was done by Scanning Electron Microscopy and the micrographs clearly indicate decreased grain size with the increasing Fe - concentration. The density of the prepared samples was done using Archimedes principle and the density values were found to be in decreasing order, which is well in agreement with the microstructure relationship. The dielectric and impedance properties have been studied at different ranges of frequency and temperature. The electrical conductivity values were found to be greater than 100 Scm-1 , which suggests it to suitable cathode material of SOFCs