Impedance Analysis of K2Pb2X2W2Ti4Nb4O30 (X = Nd, Y) Tungsten Bronze Ceramics

R. Padhee,Piyush R. Das,B. N. Parida,R. N. P. Choudhary 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.7

This paper highlights the electrical properties of two new complex tungsten bonze ceramics(K2Pb2Nd2W2Ti4Nb4O30 and K2Pb2Y2W2Ti4Nb4O30) that were prepared by using the high -temperature mixed - oxide method. The variations of impedance parameters with temperature (27− 500 C) and frequency (1 − 5 MHz) showed the grain and the grain - boundary effects in thesamples. The variations of the dielectric parameters with frequency were also studied. The variationof the ac conductivity with temperature clearly showed that the materials exhibited thermally- activated transport properties of an Arrhenius type.

Dielectric and electrical properties of a tungsten bronze tantalate ceramic

R. Padhee,Piyush R. Das,B. N. Parida,S. Behera,R. N. P. Choudhary 한국물리학회 2013 Current Applied Physics Vol.13 No.6

Using high temperature solid state reaction the polycrystalline sample of K2Pb2Dy2W2Ti4Ta4O30 was prepared. Single-phase compound formation was confirmed by preliminary X-ray structural analysis. The surface morphology recorded by scanning electron microscope at room temperature exhibits a dense uniform grain distribution on the surface of the sample. Ferroelectricity in the material is confirmed by the variation of polarization with temperature. The temperature and frequency dependence of electrical parameters (impedance, modulus, conductivity, etc.) of the material exhibits a strong correlation with its microstructure (i.e., bulk, grain boundary, etc.) and electrical properties. A typical Arrhenius behavior was observed in the temperature dependence of dc conductivity. The nature of frequency dependence of ac conductivity obeys Jonscher’s universal power law. The variation of current with temperature shows that the material has high pyroelectric coefficient and figure of merit, thus making it useful for pyroelectric sensors with working temperature upto 500 ℃.

Ferroelectric, pyroelectric and electrical properties of new tungstenebronze tantalate

B.N. Parida,Piyush R. Das,R. Padhee,R.N.P. Choudhary 한국물리학회 2013 Current Applied Physics Vol.13 No.9

The polycrystalline sample of Li2Pb2Y2W2Ti4Ta4O30 was prepared by a high-temperature solid-state reaction technique. Room temperature X-ray structural analysis confirms the formation of a single-phase compound. The surface morphology of the sintered pellet sample recorded by SEM (scanning electron microscope) exhibits a uniform grain distribution with few voids. Detailed studies of dielectric constant,tangent loss and remanent and spontaneous polarization with temperature and frequency exhibit the existence of ferroelectricity in the material. The temperature and frequency dependence of impedance parameters (impedance, modulus, etc) of the material exhibits a strong correlation between these electrical parameters with its micro-structure (i.e., bulk, grain boundary, etc). The nature of variation of pyroelectric-coefficient and current with temperature suggests that material has good pyroelectric properties useful for fabrication of pyroelectric detector.

Effect of Sm-Substitution on Structural, Electrical and Magnetic Properties of BiFeO3

Samita Pattanayak,R. N. P. Choudhary,Piyush R. Das 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.1

Samarium-modified bismuth ferrites (i.e., Bi1-xSmxFeO3 (BSFO; x = 0, 0.05, 0.15, 0.25) were synthesized in a single-phase by a solid-state reaction method. Preliminary x-ray structural analysis suggested that crystal structure of the material is rhombohedral for x = 0.0, 0.05, 0.15 and orthorhombic for x = 0.25 composition. The surface morphology and textures of the pellet samples, recorded by scanning electron microscope at room temperature, show uniform distribution of the different size of plate- and rod-shaped grains on the surface of the samples. The grain size generally decreases with increase of Sm-content in BSFO. Detailed studies of permittivity and impedance parameters of the samples in a wide frequency range (1 kHz - 1 MHz) at different temperatures (30°C - 450°C) provide many new and interesting results about relaxation processes. Room temperature magnetic hysteresis loops revealed that the spontaneous magnetization increases due to structural distortion and partial destruction of spiral spin structure caused by the substitution of Sm in BiFeO3. Enhancement in magneto-electric coupling coefficient of BFO was observed with increase of Sm in BSFO.

Structural, dielectric, electrical and magnetic properties of chemicothermally synthesized material: BiCaFeCeO6

Parida Kalpana,Choudhary R.N.P. 한국물리학회 2021 Current Applied Physics Vol.21 No.-

In this communication, detailed studies of structural, micro-structural, dielectric, electrical (impedance, modulus and conductivity) and magneto-electric characteristics of a chemico-thermally synthesized sample of a double perovskite bismuth calcium iron cerate (BiCaFeCeO6) have been reported. Preliminary structural analysis of room temperature X-ray diffraction data shows orthorhombic structure of the material. The homogeneous distribution of the grains of different dimensions (shape, size, etc) with a small number of voids observed in the scanning electron micrograph suggests the formation of high-density sample. Detailed analysis of dielectric and impedance experimental data, collected at different frequency and temperatures, have provided many important characteristics of the material, such as (a) grains, grain boundaries, and electrode dependent capacitive and impedance parameters, (b) co-relation between the structure, micro-structure and physical properties and (c) the relaxation characteristics of the tested samples. The nature of frequency dependence of AC conductivity of the material obeys the Jonscher’s universal power law. The temperature dependence of conductivity provides the conduction mechanism in the material. Detailed studies of field dependence of electric polarization, magnetization and magneto-electric coefficient at room temperature exhibit the multiferroic characteristics of the material.

Processing and Electrical Characteristics of Barium Doped CaCu3Ti4O12

Madhusmita Sahu,R. N. P. Choudhary 한국전기전자재료학회 2019 Transactions on Electrical and Electronic Material Vol.20 No.1

In this communication, the effect of a small amount of barium (15%) substitution on structural micro-structural, electrical (dielectric, impedance and conductivity) properties of CaCu3Ti4O12(i.e., Ca0.85Ba0.15Cu3Ti4O12 = CBCTO15) in different experimental conditions is presented. The polycrystalline sample of the material has been prepared by a cost-effective solidstate reaction technique. Rietveld refinement of XRD data has confirmed that the CBCTO15 sample crystallizes in cubic system bearing space group Im3. The surface micrograph depicts the dense packing of grains. The comprehensive studies of dielectric parameters [relative dielectric constant (εr), and loss tangent (tanδ)] are characterized over a wide range of temperature and frequency. The complex impedance and electrical modulus spectroscopy techniques have been employed which postulates the association of various effects (grain, grain boundary, electrode) and shed light on the conduction as well as the relaxation mechanism in the material.

Impedance and modulus spectroscopy characterization of La^+3/Mn^+4 modified PbTiO_3 nanoceramics

Archana Shukla,R.N.P. Choudhary 한국물리학회 2011 Current Applied Physics Vol.11 No.3

Nanocrystalline samples of Pb_0.92La_0.08Mn_xTi_(1-x)O_3 (PLMT) (x = 0, 0.04, 0.07, 0.10) were prepared by a high-energy ball-milling followed by a solid-state reaction method. Preliminary high resolution X-ray diffraction technique of PLMT ceramics showed that a single-phase was formed exhibiting a tetragonal crystal structure. The electrical behavior of PLMT ceramics was investigated by the impedance spectroscopy in the temperature range of 35 ℃―500 ℃. This study was carried out by means of the simultaneous analysis of the complex impedance (Z^*) and electrical modulus (M^*) functions from the measurement range of 1 kHz―1 MHz. A separation of the grain and grain boundary properties has been achieved using an equivalent circuit model in impedance analysis. Loss spectra reveal about the presence of temperature-dependent electrical relaxation phenomena in the materials. Modulus analysis provides wider information related to charge transport processes.

Microstructure, dielectric relaxation, optical, and ferroelectric studies of a lead-free double perovskite: BaLiFeMoO6

Mishra S.,Choudhary R. N. P.,Parida S. K. 한국세라믹학회 2023 한국세라믹학회지 Vol.60 No.2

In this article, the influence of co-substitution of alkali and transition metals at the Ba/Mo site of host BaMoO4 (inorganic Scheelite) is reported. A new lead-free double perovskite BaLiFeMoO6 (BLFMO) is synthesized using a conventional solid-state reaction route, having tetragonal crystal symmetry with an average crystallite size of 93.2 nm and strain of 0.115%. Grains are grown by sintering and distributed uniformly through well-defined grain boundaries as obtained from scanning electron microscopy (SEM). The purity and compositional analysis through energy-dispersive analysis X-ray spectroscopy (EDX) technique confirms the presence of constituent elements Ba, Li, Fe, Mo, and O. Raman study supports the substitution of Li/Fe atoms at Ba and Mo sites in the host matrix. Direct bandgap energy of 2.99 eV is calibrated using the ultraviolet–visible (UV–Vis) spectrum; may be suitable for photovoltaic applications. Maxwell–Wagner dielectric response, non-Debye relaxation, activation energy, and negative temperature coefficient resistance (NTCR) behavior are the outcomes of the synthesized sample characterized using dielectric, impedance, modulus, and conductivity plots in a wider spectrum of frequency (1 kHz–1 MHz) and temperatures (25–500 °C). The contribution of both grains and grain boundaries in the conduction mechanism has been investigated using Nyquist's fitting data calibrated from ZSIMPWIN software. A decrease in the magnitude of grain boundary resistance with a rise in temperature in fitted Nyquist's plot suggests the presence of semiconducting nature in the material. Analysis of leakage current density suggests that the nature of the conduction mechanism follows to the space charge limited current process. The study of temperature-dependent resistance supports BLFMO as a good candidate for NTC thermistor-related device applications. The study of polarization–electric field hysteresis loop suggests the possibility of the ferroelectric nature in the studied sample.

Structural, dielectric and impedance properties of NaCa2V5O15 ceramics

Banarji Behera,P. Nayak,R.N.P. Choudhary 한국물리학회 2009 Current Applied Physics Vol.9 No.1

Polycrystalline sample of NaCa2V5O15 (NCV) with tungsten bronze structure was prepared by a mixed oxide method at relatively low temperature (i.e. 630℃). Preliminary structural analysis of the compound showed an orthorhombic crystal structure at room temperature. Microstructural study showed that the grains are uniformly and densely distributed over the surface of the sample. Detailed studies of dielectric properties showed that the compound has dielectric anomaly above the room temperature (i.e. 289 ℃), and shows hysteresis in polarization study. The electrical parameters of the compound were studied using complex impedance spectroscopy technique in a wide temperature (23–500 ℃) and frequency (102–106 Hz) ranges. The impedance plots showed only bulk (grain) contributions, and there is a non-Debye type of dielectric dispersion. Complex modulus spectrum confirms the grain contribution only in the compound as observed in the impedance spectrum. The activation energy, calculated from the ac conductivity of the compound, was found to be 0.20–0.30 eV. These values of activation energy suggest that the conduction process is of mixed type (i.e. ionic–polaronic). Polycrystalline sample of NaCa2V5O15 (NCV) with tungsten bronze structure was prepared by a mixed oxide method at relatively low temperature (i.e. 630℃). Preliminary structural analysis of the compound showed an orthorhombic crystal structure at room temperature. Microstructural study showed that the grains are uniformly and densely distributed over the surface of the sample. Detailed studies of dielectric properties showed that the compound has dielectric anomaly above the room temperature (i.e. 289 ℃), and shows hysteresis in polarization study. The electrical parameters of the compound were studied using complex impedance spectroscopy technique in a wide temperature (23–500 ℃) and frequency (102–106 Hz) ranges. The impedance plots showed only bulk (grain) contributions, and there is a non-Debye type of dielectric dispersion. Complex modulus spectrum confirms the grain contribution only in the compound as observed in the impedance spectrum. The activation energy, calculated from the ac conductivity of the compound, was found to be 0.20–0.30 eV. These values of activation energy suggest that the conduction process is of mixed type (i.e. ionic–polaronic).

Structural, Morphological and Electrical Impedance Spectroscopy of Bi2MnCdO6 Double Perovskite Electronic Material

A. Tripathy,S. N. Das,S. Bhuyan,R. N. P. Choudhary 한국전기전자재료학회 2019 Transactions on Electrical and Electronic Material Vol.20 No.3

In this communication, the systematic studies of structural (basic crystal data, microstructure), and electrical (dielectric constant and loss, impedance, modulus, conductivity, etc.) properties of the double perovskite material Bi 2 MnCdO 6 have been reported. The compound has been synthesized by means of a high temperature route (a solid state reaction method). From the X-ray diff raction structural investigation, a stable phase of the orthorhombic crystal system has been recognized. The microstructure obtained from the scanning electron microscope shows uniform, dense and compact grain distribution. Detailed investigation of dielectric as well as electrical parameters of the fabricated compound through a broad frequency range (i.e. 1 kHz–1 MHz) and temperature (i.e., 25 °C to 300 °C) have provided many interesting data and results in order to understand its ferroelectric and electrical relaxation mechanism. It has been experimentally affi rm that this material (Bi 2 MnCdO 6 ) has more advantages like high relative dielectric constant and low tangent loss over Bi 2 MnCoO 6 material.