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A lead-free brownmillerite ferroelectric material LiBiFe2O5 (LBFO) has been synthesized via a solid-state reaction technique. Using the procedure of N-TREOR method of X-ray diffraction, the crystal structure of the prepared sample is found to be monoclinic with lattice parameters: a = 13.6726 Å, b = 4.1560 Å, c = 8.5317 Å, and β = 102.89˚. Based on analysis of electrical data, the existence of Koop's and Maxwell–Wagner relaxation phenomena and dielectric relaxation in the material has been confirmed. This analysis has also shown a high impact of the dielectric permittivity (ϵr) and low tangent loss (tanδ) on using the material in some electronic devices. A detailed study of the frequency-temperature-dependent ac conductivity has suggested the presence of Jonscher's universal power law in the material. As the material has thermistor constant (β) values of 4019.26, 11535.75, and 484.36 in different temperature ranges indicating high-temperature NTC thermistor application. [ABSTRACT FROM AUTHOR]

A newly designed lead-free complex ceramic with the chemical formula Ca3Bi2MoO9 has been synthesized using a conventional solid-state reaction technique. The structure, microstructure, resistive, dielectric, and conductivity characteristics have been experimentally tested. Analysis of the X-ray diffraction spectrum suggests the sample has monoclinic crystal symmetry (a = 10.639 Å, b = 9.674 Å, c = 6.396 Å, β = 93.794°). The lattice strain and average crystallite sizes are − 0.00114 and 24.17 nm. The compactness and quality of the material have been analyzed by FESEM and EDX spectrum. The fabricated and newly designed electronic material have effective temperature and frequency-dependent electrical characteristics. The study of the conductivity of the material confirms the Universal power law. Analysis of Impedance spectroscopy data (temperature and frequency dependent) confirms that the presence of grains and grain boundaries are responsible for the resistivity properties of the material. A depressed semicircular arc (at 450 °C) with an angle of 2.82° elaborate the non-Debye relaxation phenomena. High dielectric permittivity, minimal tangent loss, and negative temperature coefficient response are observed in the material. [ABSTRACT FROM AUTHOR]

In this communication, the synthesis (solid-state sintering) and characterization of a double perovskite BiFeMoO6 are reported. Analysis of X-ray diffraction (XRD) data provides monoclinic crystal symmetry with an average crystallite size of 85.6 nm and lattice strain of 0.00078, respectively. The microstructural analysis of the sample was done using a scanning electron microscope (SEM) and the results show that grains are well-grown and distributed uniformly throughout the sample surface. The grains are visible clearly due to well-defined grain boundaries, and the effect on the mechanism of electrical ac conductivity was studied. The compositional purity of the sample was checked by energy dispersive X-ray (EDX) analysis spectrum which supports the presence of all constituent elements (Bi, Fe, Mo and O) in both weight and atomic percentages. The study of the Ultraviolet–Visible spectrum provides a bandgap energy of 1.8 eV, suitable for photovoltaic applications. The measurements of the dielectric were used to confirm the existence of the Maxwell–Wagner type of dispersion. The study of impedance spectroscopy helps to understand the negative temperature coefficient of resistance (NTCR) character while the electrical modulus measurements claimed a non-Debye relaxation mechanism in the sample. The study of ac conductivity reveals the fact of thermally activated conduction mechanism in the sample. The presence of the semiconducting nature of the sample was checked from both Nyquist plots and Cole–Cole plots. The study of the resistance versus temperature reveals the fact of negative temperature coefficient (NTC) thermistor character and is suitable for some temperature sensor devices. [ABSTRACT FROM AUTHOR]

The sample of Bi0.9Ca0.1Fe0.9Mn0.1O3 was prepared using mechanical milling technique, and further was successively given heat treatment. The structural analysis (XRD data) suggests that the sample crystallizes in the rhombohedral (R3c) crystal structure. The co-substitution of Ca–Mn in Bismuth Ferrite (BFO) improves surface properties and enhances the reduction in particle size. A dielectric study on the sample was inspected on varying temperature and frequency range. The impedance study reveals the sturdy dependence of electrical properties on both frequencies as well temperatures having corresponded with the morphology. Room temperature ferroelectric hysteresis (P-E) loop shows the presence of ferroelectricity and a small reduction in leakage current was detected. The magnetic measurement divulges the enrichment in magnetization because of the distortion in structure and partial destruction of spin cycloid originating from co-substitution. The extent of interaction between the dipoles present in the ceramics can be estimated by the calculation of M-E coupling coefficient. The existence of ferroelectricity, ferromagnetism, and magneto-electric effect in the sample supports the strong enhancement in the multiferroism and magneto-electric coupling of BFO. [ABSTRACT FROM AUTHOR]

Double pervoskite BiHoZnCeO6 (BHZCO) has been synthesized by the cost-effective solid state reaction method. It is characterized by a combination of techniques including powder X-ray diffraction (PXRD), dielectric, thermal analysis, and scanning electron microscopy (SEM). The fundamental structural symmetry and the cell parameter refinement for the BHZCO is investigated by analyzing the PXRD data with the help of widely used "MAUD" software. As per the PXRD-analysis, the Fig. 1a and b of the published paper Applied Physics A (2020) 126:655, clearly shows that it crystallizes with an orthorhombic crystal lattice with space group of Pca21, whose profile resembles with another bismuth-based double pervoskite Bi2WO6; crystallography open database (COD) ID: 2,108,252. However, in the CP paper, the author claims that BHZCO should have the cubic Fm-3m crystal structure, surprisingly claims that the phase is CeO2:Bi,Ho,Zn with unknown amount of dopants. Hence, in the present communication attempts have been made to compare both the cell structures for the BHZCO. [ABSTRACT FROM AUTHOR]

Scalability and miniaturization of suitably tailored dielectric material for integration with device industry is at the crux of research in material science. In the present communication rare earth copper oxides belonging to the family of R2BaCuO5 where R = Gd and Dy are synthesized via conventional solid state reaction route. Preliminary phase confirmation of the synthesized samples is accomplished using room temperature X-ray diffraction data. The green phase copper oxides of gadolinium and dysprosium calcined at 950 °C are shown (as graphical insets) in X-ray diffractogram. Micro-structural study from the scanning electron micrograph obtained at a magnification of 10,000X shows uniform distribution of grains with prominent grain boundaries. Furthermore energy dispersive X-ray analysis (EDX) spectrum and elemental data confirms presence of all the required elements in the samples. The small values (less than one) of dielectric loss at room and higher temperatures at 1 MHz frequency make them potential candidates (as low-loss high-frequency components) for various electronic devices. Dielectric anomalies observed in Gd2BaCuO5 and Dy2BaCuO5 are attributed to oxygen vacancies induced relaxation behaviour. The universal Jonscher power law has been employed to discern the probable conduction mechanisms involved in the samples within the measured temperature (25 °C to 500 °C) and frequency range (1 kHz to 1 MHz) range. Both the synthesized samples exhibit correlated barrier hopping (CBH) as well as non-overlapping small polaron tunneling (NSPT) mechanism. The activation energy values obtained from the temperature dependent conductivity fitted to Arrhenius equation propound the presence of single and double ionized oxygen vacancies in the materials. Besides ac conductivity behaviour, an impedance spectroscopic study also reveals the existence of temperature dependent electrical relaxation accompanied with distribution of relaxation times. The values of grain and grain boundary resistance and capacitance values are obtained from the Nyquist plot fitted to (RQC), (RC-RQC) and (RQC-RQC) circuits. Non-Debye type of relaxation is observed in the samples and the deviation from the Debye behaviour is expressed in the form of depression angles. [ABSTRACT FROM AUTHOR]

In this paper, detailed studies of structural, micro-structural, dielectric, electrical and magneto-electric characteristics of chemically synthesized a new double perovskite, BiSrFeCeO6 (strontium cerate-modified bismuth ferrite), are reported. The basic crystal data (unit cell dimension and orthorhombic crystal system) of the compound were obtained by analysing the room temperature X-ray powder diffraction data. Study of the surface microstructure of a sintered pellet sample, recorded by scanning electron microscope at room temperature, reveals the formation of high-density sample with the homogeneously and uniformly distributed grains of different size and shape. Analysis of frequency-temperature dependence of dielectric parameters and nature of hysteresis loop has exhibited the ferroelectric characteristics of the material. Studies of complex impedance and modulus components at different temperatures and frequencies have provided electrical characteristics of grains and grain boundaries present in the material, which are closely related to its microstructure. Thus, the correlation between the crystal structure with electrical properties and relaxation mechanism of the prepared sample has been established. The type of dielectric relaxation process and mechanism occurred in the compound have also been studied not only by analysis of the dielectric properties (εr, tan δ) and impedance parameters, but also from the study of frequency-temperature conductivity. The existence of negative temperature coefficient of resistance (NTCR) characteristics in the material has been confirmed from the temperature and dc conductivity analysis. Similarly, the frequency and ac conductivity analysis show that the studied compound follows Jonscher's universal power law. Based on the structural, ferroelectric, magnetic and magneto-electric characteristics, multiferroism in the new composition of bismuth ferrite has been established. [ABSTRACT FROM AUTHOR]

In this paper, detailed studies of structural, micro-structural, dielectric, electrical and magneto-electric characteristics of chemically synthesized a new double perovskite, BiSrFeCeO6 (strontium cerate-modified bismuth ferrite), are reported. The basic crystal data (unit cell dimension and orthorhombic crystal system) of the compound were obtained by analysing the room temperature X-ray powder diffraction data. Study of the surface microstructure of a sintered pellet sample, recorded by scanning electron microscope at room temperature, reveals the formation of high-density sample with the homogeneously and uniformly distributed grains of different size and shape. Analysis of frequency-temperature dependence of dielectric parameters and nature of hysteresis loop has exhibited the ferroelectric characteristics of the material. Studies of complex impedance and modulus components at different temperatures and frequencies have provided electrical characteristics of grains and grain boundaries present in the material, which are closely related to its microstructure. Thus, the correlation between the crystal structure with electrical properties and relaxation mechanism of the prepared sample has been established. The type of dielectric relaxation process and mechanism occurred in the compound have also been studied not only by analysis of the dielectric properties (εr, tan δ) and impedance parameters, but also from the study of frequency-temperature conductivity. The existence of negative temperature coefficient of resistance (NTCR) characteristics in the material has been confirmed from the temperature and dc conductivity analysis. Similarly, the frequency and ac conductivity analysis show that the studied compound follows Jonscher's universal power law. Based on the structural, ferroelectric, magnetic and magneto-electric characteristics, multiferroism in the new composition of bismuth ferrite has been established. [ABSTRACT FROM AUTHOR]

Scalability and miniaturization of suitably tailored dielectric material for integration with device industry is at the crux of research in material science. In the present communication rare earth copper oxides belonging to the family of R2BaCuO5 where R = Gd and Dy are synthesized via conventional solid state reaction route. Preliminary phase confirmation of the synthesized samples is accomplished using room temperature X-ray diffraction data. The green phase copper oxides of gadolinium and dysprosium calcined at 950 °C are shown (as graphical insets) in X-ray diffractogram. Micro-structural study from the scanning electron micrograph obtained at a magnification of 10,000X shows uniform distribution of grains with prominent grain boundaries. Furthermore energy dispersive X-ray analysis (EDX) spectrum and elemental data confirms presence of all the required elements in the samples. The small values (less than one) of dielectric loss at room and higher temperatures at 1 MHz frequency make them potential candidates (as low-loss high-frequency components) for various electronic devices. Dielectric anomalies observed in Gd2BaCuO5 and Dy2BaCuO5 are attributed to oxygen vacancies induced relaxation behaviour. The universal Jonscher power law has been employed to discern the probable conduction mechanisms involved in the samples within the measured temperature (25 °C to 500 °C) and frequency range (1 kHz to 1 MHz) range. Both the synthesized samples exhibit correlated barrier hopping (CBH) as well as non-overlapping small polaron tunneling (NSPT) mechanism. The activation energy values obtained from the temperature dependent conductivity fitted to Arrhenius equation propound the presence of single and double ionized oxygen vacancies in the materials. Besides ac conductivity behaviour, an impedance spectroscopic study also reveals the existence of temperature dependent electrical relaxation accompanied with distribution of relaxation times. The values of grain and grain boundary resistance and capacitance values are obtained from the Nyquist plot fitted to (RQC), (RC-RQC) and (RQC-RQC) circuits. Non-Debye type of relaxation is observed in the samples and the deviation from the Debye behaviour is expressed in the form of depression angles. [ABSTRACT FROM AUTHOR]

The preliminary structural and frequency-temperature dependence of dielectric and electrical characteristics of Ba/Zr modified Bismuth ferrite(BiFeO3) i.e.(Bi1-xBax)(Fe1-xZrx)O3; x = 0.05, 0.1, 0.15, 0.20 at room temperature have been reported. The samples are produced in a perovskite rhombohedral structure, according to the X-ray diffraction pattern and analysis of room temperature XRD data. The SEM photographs are useful for the micro-structural view of the synthesized compounds. Dielectric and electrical characteristics across a wide temperature range 25 °C to 300 °C at different frequencies ranging from 1 kHz to 1 MHz have provided many important results including dielectric dispersion, conduction mechanism, relaxation process and ferroelectricity of the prepared samples. The contributions of grains and grain boundaries towards the net resistance and capacitance of the samples are found from the Nyquist plots. The types of conduction mechanism have been studied from ac-conductivity study of the samples. The Ohmic behaviour is verified by the J–E characteristics of the prepared samples, which have a slope closer to 1. The electrical polarization study through hysteresis loops at room temperature confirms the ferroelectric behavior of the studied materials. According to the experimental results obtained here, the synthesized materials could be beneficial as electronic components in the electronic industries. [ABSTRACT FROM AUTHOR]