Low-frequency Dielectric Response Research Articles

A holistic understanding of optical properties in amorphous H-terminated Si-nanostructures: Combining TD-DFT with AIMD

Silicon, traditionally known as an indirect band gap semiconductor, unveils intriguing properties at the nanoscale, stemming from deviations from k-conservation rules within nanostructures. In our study, we scrutinized four hydrogenated Si 0D-nanostructures—Si10H16, Si14H20, Si18H24, and Si22H28—to unravel their dynamic stability under thermal fluctuations and optical characteristics. We initiated our exploration by employing the TD-DFT framework to generate and analyze the optical properties of these geometrically optimized nanostructures. Simultaneously, we conducted ab initio molecular dynamics simulations to examine the structural robustness and thermal stability of the four structures. Leveraging the Car-Parrinello molecular dynamics approach within the Quantum ESPRESSO open software suite, we observed temperature evolution and stability differences among the nanostructures at targeted temperatures 40 and 300 K. Our subsequent investigation delved into the Turbo-Lanczos time-dependent DFT method, unraveling the optical properties and excited-state dynamics of hydrogenated Si nanostructures. The results unveiled shifts towards higher energy absorption edges E0, accompanied by alterations in the permittivity tensor, complex refractive index, oscillator strength, and reflectivity. Notably, the analysis revealed an enlarged HOMO-LUMO gap, distinctive from bulk Si. Furthermore, our models predicted the elimination of phase-dependent E1/E2 optical transition peaks in the imaginary part of the dielectric function, and a gradual decrease in the low-frequency dielectric response with increased hydrogenation of the amorphous structures. These findings underscore the promising applications of hydrogenating Si nanostructures in diverse technological domains such as optoelectronics, memristors, sensors, and quantum computing. Their tunable optical properties, size-dependent behaviors, and compatibility with existing silicon-based devices make them particularly appealing for next-generation technologies.

Dielectric spectrum of a ferrofluid layer exposed to a gradient magnetic field.

A low-frequency dielectric response of a ferrofluid based on transformer oil and MnZn ferrite nanoparticles is investigated in a gradient magnetic field. Four ferrofluid samples of various nanoparticle concentrations were introduced into planar micro-capacitors located over a magnetized tip. The dielectric spectra were measured in the frequency range from 0.1Hz to 200kHz and in the local magnetic field up to 100 mT. The spectra exhibit a dielectric relaxation ascribed to nanoparticle interfacial polarization. The low-frequency spectrum of each ferrofluid decreases upon application of the magnetic field up to 20 mT. The decrease in dielectric permittivity is caused by a magnetic force acting on larger nanoparticles in the gradient magnetic field. It is assumed that the interfaces of the concentrated nanoparticles in the gradient field do not contribute to the effective dielectric response. This reduces the effective relaxation time and shifts the relaxation toward higher frequencies. The dielectric spectra are well described by a relaxation fit function consisting of one Havriliak-Negami and a conductivity term. The fitting confirms that the only effect of the gradient magnetic field on the dielectric spectra is the shift of the dielectric relaxation and the decrease of the amplitude in the imaginary permittivity. This behavior is evident from a master plot, where all dielectric relaxations are superimposed on a single line. The knowledge of the presented behavior of the ferrofluid may be valuable when applying a ferrofluid to sharply magnetized parts of various electrical equipment (wires, tips, screws, nails, edges) as a liquid dielectric medium.

Analysis of High-Temperature Wideband Dielectric Properties of ATH-Filled Silicone Rubber Used for On-Site Insulation of Bare Overhead Conductors

Due to its excellent electrical and mechanical properties, and easy to cure at room temperature, room temperature vulcanizing silicone rubber is currently used in the on-site insulation of bare overhead conductors in the distribution system. The dielectric properties of silicone rubber materials have a great impact on power loss, which is vital to the transmission lines. Therefore, in this article, the dielectric properties of silicone rubber with the addition of different aluminum hydroxide contents are investigated by broadband dielectric spectroscopy in wide broadband range and wide temperature ranges, and the influence of aluminum hydroxide filler on the dielectric response is analyzed using a modified Cole–Cole model which takes the low-frequency dispersion process into account. It is found that the relationship of the dc conductivity and the low-frequency dispersion strength with temperature follows the Arrhenius equation law. The low-frequency dielectric response is influenced by dipoles’ polarization and electrode polarization. Moreover, the relaxation time decreases with the increase in temperature, and its mechanism can be revealed by the double-well model. The characteristic parameters obtained in this article can provide a reference for on-site insulating of bare overhead conductors.

Low frequency dielectric response mechanism of bamboo charcoal

The carbonization of bamboo at 400 °C–700 °C resulted in the formation of graphite crystals embedded in amorphous carbon. The high dielectric constants (≈103 at 1 Hz) of these carbon materials were attributed to the presence of polar groups such as -OH, -NH2 and -COOH with marginal contribution from interfacial polarization. The dielectric constants were observed to be frequency-dependent and found to be decreased with increasing frequency. The measured dielectric loss was also found to be decreasing with increasing frequency. Conductance dominant dielectric loss observed in 400 °C–600 °C annealed samples was further supported by the Cole-Cole plot. Maxwell–Wagner–Sillars interfacial polarization relaxation along with conduction loss was observed only for the 700 °C annealed sample.

Enhancement of dielectric response by the interaction of point defect and grain boundary in copper tantalate oxides

As particular cubic perovskite-type materials, copper tantalate Cu2Ta4O12 (CTO) displays a giant-dielectric phenomenon. A thermal-treatment method for enhancing the dielectric response of CTO is developed. The air-quenching Cu2Ta4O12 (CTOq) and slowing-furnace-cooling Cu2Ta4O12 (CTOs) were fabricated and identified with cubic crystal structure. The CTOs sample shows a colossal permittivity (104 - 107) in a broad frequency (40 Hz–105 Hz) and temperature region (300 K–470 K). The permittivity dependence of frequency for CTOq and CTOs samples were described by the Maxwell-Wagner relaxation and Cole-Cole relation. The low-frequency dielectric response associates with the internal barrier layer capacitor effect intensified by oxygen vacancies, while in the high-frequency range it is mainly involved in the relaxation induced by charged point defects in grains. The concentration of the point defects was evidenced by XPS with Cu+, Cu2+ and oxygen. The impedance, electrical modulus and conductivity behavior of the samples at selected temperature were also described. The results indicate that the colossal permittivity response is related to interaction mechanism of point defects and grain boundaries, which can be modified by the thermal treatment process.

VLF Dielectric Response and HF Localized Dielectric Discharge Measurement for Rotating Machine Insulation Assessment

This paper represents the very low frequency (VLF) dielectric response and high frequency (HF) localized dielectric discharge measurement for rotating machine insulation assessment. The integral conditions of stator winding insulation, the so-called aging condition, were investigated by the dielectric response measuring technique. The polarization and depolarization currents in the VLF range from 0.0001 to 1 Hz were measured under an external step electric field. The local conditions of stator winding insulation, the so-called weak spot condition, were examined by the partial discharge (PD) measuring technique. The PD pulse currents were detected by a capacitive sensor in a wide-band range, where the bandwidth of the measuring system was set between 30 kHz and 30 MHz. The medium voltage rotating machine rated 6.6 kV and 240 to 2,270 kW under different service conditions, i.e., new stator winding, moisture contamination, dirt contamination as well as thermally and severely aged insulation, was studied. Besides, four case studies on measuring the PD in service rotating machines rated 11–15 kV, 7100 to 211,000 kW as well as the attenuation of the PD pulses were conducted and demonstrated. With several case studies, this paper introduces new dielectric parameters, the so-called charge ratio (QR) and charge difference gradient (QDG), to identify the dielectric mechanism occurring in the stator winding insulation caused by the polarization and conduction processes. It can be concluded that the proposed parameters are a valuable tool for assessing the aging condition. In the case of the PD measurement, it was found that the PD pulse is strongly attenuated in the slot section. This paper also introduces the combination of both the dielectric response and PD measurement results, which can be very useful for assessing a complete insulation condition in the rotating machine. Moreover, the criteria for insulation conditions are suggested in this paper to evaluate the integral and local conditions for the rotating machine insulation. The local discharge in the machine causes electromagnetic waves, which may get released from the non-perfect characteristics of the enclosure. This signal may interfere with the functioning of other nearby electronic devices, especially the communication equipment. Therefore, maintaining the excellent condition of the insulation system by the proposed technique detailed in this paper will support the highly effective operational efficiency of the communication system as well.

Investigation on structural, hysteresis, Mössbauer properties and electrical parameters of lightly Erbium substituted X-type Ba2Co2ErxFe28-xO46 hexaferrites

A series of Erbium substituted X-type Ba2Co2ErxFe28-xO46 (x = 0.00, 0.04, 0.08, 0.12, 0.16, and 0.20) hexaferrites were prepared by the method of heat treatment. The obtained precursors were heated at 1350 °C for 6 h. XRD investigation reveals that x = 0.0 sample possesses X, W-type, and α-Fe2O3 phases, while Er- substituted samples show presence of X and W phases. The room temperature Mössabuer spectra have been fitted with five sextets. A variation in saturation magnetization (MS) is explained and supported by the Mössbauer spectroscopy. The maximum values of MS (52.29 Am2/kg) and anisotropy field-Ha (1370 kA/m) are found for x = 0.12 composition. Similarly, the maximum relative area (~69%) for spin up sites (k+a+b) is also found for x = 0.12 composition. Low frequency (20 Hz–2 MHz) dielectric response of all samples show normal behavior of ferromagnetic materials. The dielectric measurements reveal that the conduction in low frequency is due to grain boundary contributions and at the higher frequency it is due to grain contributions. AC conductivity is found to increase with frequency in all prepared hexaferrites. The substituted compositions can have potential applications in filter application due to soft ferrite behavior and low dielectric loss tangent.

Light-Enhanced Ion Migration in Two-Dimensional Perovskite Single Crystals Revealed in Carbon Nanotubes/Two-Dimensional Perovskite Heterostructure and Its Photomemory Application.

Two-dimensional (2D) hybrid perovskite sandwiched between two long-chain organic layers is an emerging class of low-cost semiconductor materials with unique optical properties and improved moisture stability. Unlike conventional semiconductors, ion migration in perovskite is a unique phenomenon possibly responsible for long carrier lifetime, current–voltage hysteresis, and low-frequency giant dielectric response. While there are many studies of ion migration in bulk hybrid perovskite, not much is known for its 2D counterparts, especially for ion migration induced by light excitation. Here, we construct an exfoliated 2D perovskite/carbon nanotube (CNT) heterostructure field effect transistor (FET), not only to demonstrate its potential in photomemory applications, but also to study the light induced ion migration mechanisms. We show that the FET I–V characteristic curve can be regulated by light and shows two opposite trends under different CNT oxygen doping conditions. Our temperature-dependent study indicates that the change in the I–V curve is probably caused by ion redistribution in the 2D hybrid perovskite. The first principle calculation shows the reduction of the migration barrier of I vacancy under light excitation. The device simulation shows that the increase of 2D hybrid perovskite dielectric constant (enabled by the increased ion migration) can change the I–V curve in the trends observed experimentally. Finally, the so synthesized FET shows the multilevel photomemory function. Our work shows that not only we could understand the unique ion migration behavior in 2D hybrid perovskite, it might also be used for many future memory function related applications not realizable in traditional semiconductors.

Modelling the low‐frequency electrode dielectric response based on transformer equivalent oil‐paper insulation model

The oil-impregnated transformer is an important part of the power system. The ageing degree of the internal oil-paper insulation determines the service life of the transformer. The low frequency of the frequency domain dielectric spectroscopy can effectively characterise the ageing degree of transformer oil-paper insulation. For accurately and quantitatively evaluate the aging state of oil-paper insulation of transformer, the physical process of low-frequency electrode polarisation is theoretically analysed in this work. Considering the polarisation of the low-frequency electrode, the theoretical expression of the dielectric response of the equivalent XY model of the transformer is obtained. Meanwhile, to verify the rationality of the theoretical expression, the accelerated thermal ageing test of the oil-paper insulation samples were carried out under laboratory conditions. The DC conductivity, ion mobility and FDS tests of oil-paper insulation samples were tested on ageing 5, 10 and 15 days, respectively. The test results were combined with the theoretical expression of the low-frequency dielectric response. It is found that the difference between the calculated result and the measured result is small. Therefore, the theoretical expression of the transformer equivalent XY model can be applied to calculate the dielectric parameters of the oil-paper insulation at low-frequency.

Ni nanocrystals tuning low-frequency colossal permittivity of epitaxial BaTiO3 matrix

The ceramic-metal composites (CMCs) with colossal permittivity have great potential to be widely applied into embedded capacitors. However, the colossal permittivity of these composites could not be explained in the low-frequency region (<100 Hz) due to the uncontrollable grains and grain boundaries in the polycrystalline ceramic matrix. In this work, Ni nanocrystals (NCs) were embedded in epitaxial BaTiO3 films. According to modulate the interfacial stress, the epitaxial growth of BaTiO3 was not disturbed by the NCs, avoiding the influence of grains and grain boundaries in polycrystalline oxides matrix. By tuning the spacing of NCs, the controllable distribution of grain (Ni NCs) and grain boundary (contact interface between the Ni and BaTiO3) was realized. The effects of grain and grain boundary on the low-frequency colossal dielectric response of CMCs were revealed. This study provides an ideal CMCs model for designing and application of new thin-layer capacitors.

Soft mode driven local ferroelectric transition in lead-based relaxors

Recently, we have analyzed the complex infrared (IR) and terahertz (THz) response of the relaxor ferroelectric Pb(Mg1/3Nb2/3)O3 (PMN) and suggested a new interpretation of the so-called intermediate temperature T* ≈ 400 K, where the split soft phonon mode undergoes incomplete softening. IR-THz reflectivity was fitted using effective medium approximation, which describes the uniaxially anisotropic response of polar nanodomains (PNDs). It indicated that the response perpendicular to the local polarization undergoes a classical Cochran softening toward T* with the extrapolated low-frequency permittivity obeying the Curie-Weiss (CW) law with TC ≈ T*. In this letter, we report analysis performed in a similar way on the published IR-THz response in closely related relaxor Pb(Mg1/3Ta2/3)O3 and have revealed a similar behavior: The lowest-frequency phonon polarized perpendicularly to the local polarization of PNDs softens below ∼900 K according to the Cochran law and the corresponding low-frequency permittivity obeys the CW law with TC = 340 K ≈ T* and Curie constant C = 1.16 × 105 K. This is comparable to similar parameters for PMN, TC = 380 K ≈ T* and C = 1.7 × 105 K. This explains the high-temperature CW anomaly in the low-frequency dielectric response of both materials and strongly suggests that both relaxors undergo a local ferroelectric phase transition near T* which induces a new polarization component perpendicular to the local random electric field.

Low-frequency dielectric response of a periodic array of charged spheres in an electrolyte solution: The simple cubic lattice.

We study the low-frequency dielectric response of highly charged spheres arranged in a cubic lattice and immersed in an electrolyte solution. We focus on the influence of the out-of-phase current in the regime where the ionic charge is neutral. We consider the case where the charged spheres have no surface conductance and no frequency-dependent surface capacitance. Hence, the frequency dispersion of the dielectric constant is dominated by the effect of neutral currents outside the electric double layer. In the thin double-layer limit, we use Fixman's boundary condition at the outer surface of the double layer to capture the interaction between the electric field and the flow of the ions. For periodic conditions, we combine the methods developed by Lord Rayleigh for understanding the electric conduction across rectangularly arranged obstacles and by Korringa, Kohn, and Rostoker for the electronic band structure computation. When the charged spheres occupy a very small volume fraction, smaller than 1%, our solution becomes consistent with the Maxwell Garnett mixing formula together with the single-particle polarization response, as expected, because interparticle interactions become less prominent in the dilute limit. By contrast, the interparticle interaction greatly alters the dielectric response even when charged spheres occupy only 2% of the volume. We found that the characteristic frequency shifts to a higher value compared to that derived from the single-particle polarization response. At the same time, the low-frequency dielectric enhancement, a signature of charged spheres immersed in an electrolyte, becomes less prominent for the periodic array of charged spheres. Our results imply that the signature of the dielectric response of a system consisting of densely packed charged spheres immersed in an electrolyte can differ drastically from a dilute suspension.

Understanding the validity of impedance and modulus spectroscopy on exploring electrical heterogeneity in dielectric ceramics

Combined modulus and impedance spectra are widely employed to explore electrical inhomogeneity and carriers' behaviors in dielectric ceramics based on equivalent circuit. However, discrepancies are found between practical dielectric responses and widely proposed equivalent circuits. Taking ZnO varistor ceramics as an example, a low-frequency dielectric relaxation, which can be detected in practical dielectric spectroscopy, is overlooked in simulated dielectric spectroscopy based on the proposed equivalent circuit according to modulus and impedance spectra. Therefore, equivalent circuits are frequently incomplete because the real low-frequency dielectric response is unable to be characterized from them. The problem originates from debatable understanding of frequency responses in modulus and impedance spectra. The low-frequency peak in modulus spectroscopy is proved originating from DC conductance instead of a real dielectric relaxation and the involvement of DC conductance component makes a low-frequency dielectric relaxation unable to be characterized in modulus spectroscopy. Therefore, improved dielectric spectroscopy eliminating the component of DC conductance is proposed and a clear peak corresponding to the low-frequency dielectric relaxation appears. In addition, a modified equivalent circuit which is in accordance with practical dielectric responses in not only modulus and impedance spectra but also dielectric spectroscopy is presented.

Electrical characterization of epoxy-based molding compounds for next generation HV ICs in presence of moisture

The effects of moisture on the electrical properties of epoxy molding compounds containing high quantities of silica filler microparticles have been investigated by means of dielectric spectroscopy, steady-state conductivity and pulsed electro-acoustic space charge measurements. It has been shown that the presence of water at the filler/epoxy interfacial areas affects the low-frequency dielectric response of the materials and significantly increases their electrical conductivity, especially at higher temperatures. In addition, in presence of moisture, space charge measurements have shown the accumulation of heterocharges which significantly increase the electric field at the electrodes. These aspects are of primary importance, as the electrical properties of the encapsulation materials strongly influence the space charge distribution in high voltage devices.

Origin of giant permittivity in Ta, Al co-doped TiO2: Surface layer and internal barrier capacitance layer effects

In order to achieve optimized electric properties, Ta, Al co-doped TiO2 was researched by carefully tuning the composition of ceramics in this work. X-ray diffraction patterns and Raman spectra co-evidenced that all samples were in pure tetragonal rutile TiO2. (Al0.5Ta0.5)0.08Ti0.92O2 ceramics showed relatively good dielectric properties including a colossal permittivity (CP) over 104, a low dielectric loss (0.05) and a good temperature stability. Especially, physical origins of giant permittivity were explored by a combined analysis of impedance spectroscopy, XPS and reflection spectra. Impedance and modulus spectrum verified three relaxation peaks indicating the electronic heterogeneity of materials. Combined with nonlinear I-V behavior, it can be concluded that the origin of the CP was attributed to the internal barrier layer capacitance (IBLC) effect. In addition, based on the results of XPS and reflection spectra, significant changes of oxygen vacancy and Ti3+ concentration were observed for the samples with different thickness, which further proved the contribution of surface layer effect to low-frequency dielectric response. Finally, the CP of (Al0.5Ta0.5)xTi1-xO2 ceramics were attributed to a synergy effect of the IBLC and surface layer effect.

Dielectric relaxation and conduction mechanism of complex perovskite Ca0.90Sr0.10Cu3Ti3.95Zn0.05O12 ceramic

In this work, Sr and Zn co-doped calcium copper titanate having nominal formula Ca0.90Sr0.10Cu3Ti3.95Zn0.05O12 has been synthesized and systematically studied for structure, dielectric and electrical properties. The phase purity of the prepared composition has been confirmed by X-ray diffraction (XRD) pattern and various structural parameters are presented here with Rietveld refinement data. The Scanning electron microscopy (SEM) image revealed the presence of homogeneous fine-grained microstructure investigated in the prepared ceramic. The impedance data well fitted with 2 R-CPE model confirmed the non-ideality of the system. Dielectric studies have shown the existence of two relaxation processes in low and high frequency domains. Low frequency dielectric response proposed as a combination of Maxwell-Wagner relaxation and intrinsic defect (Vo++) while high frequency behavior has been interpreted in terms of polaronic relaxation caused by hopping process of an electron between Ti3+ and Ti4+ states. The frequency dependent behavior of conductivity has been well fitted to Dong’s model and interpreted in term of Overlapping Large Polaron Tunneling (OLPT) mechanism. The various parameters; relaxation angular frequency (ω1) of Debye process, ionic hopping frequency (ω2), dc conductivity (σo), cole- cole parameter (α) and frequency exponent (s) have been determined by Dong’s Model fitting.

Low-frequency dielectric response of charged oblate spheroidal particles immersed in an electrolyte.

We study the low-frequency polarization response of a surface-charged oblate spheroidal particle immersed in an electrolyte solution. Because the charged spheroid attracts counterions which form the electric double layer around the particle, using usual boundary conditions at the interface between the particle and electrolyte can be quite complicated and challenging. Hence, we generalize Fixman's boundary conditions, originally derived for spherical particles, to the case of the charged oblate spheroid. Given two different counterion distributions in the thin electric double-layer limit, we obtain analytic expressions for the polarization coefficients to the first nontrivial order in frequency. We find that the polarization response normal to the symmetry axis depends on the total amount of charge carried by the oblate spheroid while that parallel to the symmetry axis is suppressed when there is less charge on the edge of the spheroid. We further study the overall dielectric response for a dilute suspension of charged spheroids. We find that the dielectric enhancement at low frequency, which is driven by the presence of a large ζ potential (surface charge), is suppressed by high ion concentrations in the electrolyte and depends on the size of the suspended particles. In addition, spheroids with higher aspect ratios will also lead to a stronger dielectric enhancement due to the combination of the electric double layer and textural effects. The characteristic frequency associated with the dielectric enhancement scales inversely with the square of the particle size, the major radius of the spheroid, and it has a weak dependence on the shape of spheroids.

Modelling the low‐frequency dielectric response test of insulation oil

The frequency domain dielectric response method has been one of the most effective approaches for condition assessment of an electrical insulation system. The low-frequency part is more effective for diagnosing the moisture content and aging status of oil-paper insulation. To facilitate the study of the low-frequency dielectric spectrum of oil-paper insulation, a model applicable to the low-frequency dielectric response of insulation oil is proposed in this study, which is based on the ionic motion of insulation oil. The creation of charge carriers under field test conditions mainly derives from the dissociation of ionic pairs. During testing, ionic motion of insulation oil is jointly affected by thermal diffusion and the electric field; moreover, dissociation and recombination of negative and positive ions also occur. Therefore, the above factors were all considered in the modelling process. The applicability of the model is verified against measured results. For further interpreting the proposed model, the characteristics of the ionic concentration distribution, the relation between ionic distribution and dielectric properties, and the application of the proposed model are analysed.

Reversible Structural Swell-Shrink and Recoverable Optical Properties in Hybrid Inorganic-Organic Perovskite.

Ion migration in hybrid organic-inorganic perovskites has been suggested to be an important factor for many unusual behaviors in perovskite-based optoelectronics, such as current-voltage hysteresis, low-frequency giant dielectric response, and the switchable photovoltaic effect. However, the role played by ion migration in the photoelectric conversion process of perovskites is still unclear. In this work, we provide microscale insights into the influence of ion migration on the microstructure, stability, and light-matter interaction in perovskite micro/nanowires by using spatially resolved optical characterization techniques. We observed that ion migration, especially the migration of MA(+) ions, will induce a reversible structural swell-shrink in perovskites and recoverably affect the reflective index, quantum efficiency, light-harvesting, and photoelectric properties. The maximum ion migration quantity in perovskites was as high as approximately 30%, resulting in lattice swell or shrink of approximately 4.4%. Meanwhile, the evidence shows that ion migration in perovskites could gradually accelerate the aging of perovskites because of lattice distortion in the reversible structural swell-shrink process. Knowledge regarding reversible structural swell-shrink and recoverable optical properties may shed light on the development of optoelectronic and converse piezoelectric devices based on perovskites.

Investigations on Dielectric phase transition behavior of Pb(Fe0.5-xScx)Nb0.5O3 Multiferroic Ceramics

ABSTRACTPhase pure Pb[(Fe0.5-xScx)Nb0.5]O3 [x = 0 to 0.5] multiferroic relaxors have been synthesized to study the effect of Sc on dielectric phase tansition. Rietveld refinement of x-ray diffraction patterns confirm that the structure transforms from monoclinic (Cm) to rhomobohedral (R3m) at x = 0.3. Absence of low frequency dielectric response in compositions with low Sc content attributed to interfacial polarizabilty arising due to differences in conductivities of grain and grain boundary. Moreover, value of diffusivity parameter (γ) of high of Sc content compositions is near to 2, confirms relaxor charactertistic of these compositions. However, an essential feature of relaxors i.e., frequency dependent dielectric permittivity as a function of temperature is observed only in x = 0.5 composition [Pb(Sc0.5Nb0.5)O3 (PSN)]. In addition, ferroelectric phase transition temperature (Tmax) increases initially at lower Sc content (upto x ≤ 0.25), and further drops beyond x ≥ 0.3. Such behavior of Tmax in these compositions is due to the onset of B'-B" local cation ordering at x = 0.3. High temperature Raman spectra of Pb(Sc0.5Nb0.5)O3 (x = 0.5) confirm the stability of cation ordering in compositions with high Sc content well above the phase transition temperature.