Conductivity Relaxation Process Research Articles

Study of microstructure and electrical conduction mechanisms of quaternary semiconducting glassy systems: Effect of mixed modifiers

In this work, we have investigated microstructural, optical properties, and electrical conduction mechanism of two ternary and four quaternary glassy systems of 0.65ZnO–0.1P2O5–0.25 [xTeO2–(1-x) MoO3] composition to uncover a more reliable semiconductor nanocomposite system for various types of suitable applications. XRD patterns and TEM micrographs reveal the presence of amorphous phases with a few superposed nanocrystallites. The optical bandgap energy (Eopt) values, obtained from UV-Vis spectra, vary with TeO2 concentration (x), and an inverse relationship between Eopt and average nanocrystallite size (dC) is identified. It is detected that DC and AC conductivity increase as temperature rises, manifesting a semiconducting feature. DC conductivity shows non-linearity and caused by the small polaron hopping process, whereas the modified correlated barrier-hopping (CBH) model is the applicable mechanism for AC conductivity. Scaled spectra of conductivity unveil that the conductivity relaxation process depends on the composite structure and does not depend on temperature.

Influence of MWCNTs/Li-doped TiO2 nanoparticles on the structural, thermal, electrical and mechanical properties of poly (ethylene oxide)/poly (methylmethacrylate) composite

MWCNTs/Li-doped TiO2 nanoparticles were synthesized via a sol-gel process from MWCNTs, titanium isopropoxide (Ti (OPr)4, and LiCl4. The XRD analysis confirmed the formation of MWCNTs/Li-doped TiO2 NPs. The EDX spectroscopy spectrum indicated the existence of carbon, oxygen, and titanium signals as the components of the synthetic composite. TEM shows of the MWCNTs/Li-doped TiO2 NPs like a cube, tetragonal and hexagonal shapes with an average particle size 5–35 nm. The polymer nanocomposite samples based on PEO and PMMA with MWCNTs/Li-doped TiO2 as the dopant at variation contents have been prepared via casting method. The optical, structural, mechanical and electrical properties of the prepared samples were achieved via different techniques. From the XRD results, reveal the amorphous nature of PEO/MMA decrease with MWCNTs/Li-doped TiO2 doping. The FT-IR confirmed the presence interaction between MWCNTs/Li-doped TiO2 and polymer blend. It’s observed the optical energy gap values (indirect and direct) for all samples decrease with increase in filler concentration by UV. Vis analysis. The TGA reveals improve in the thermal stability of nanocomposites compared to PMMA/PEO. The conductivity after addition filler to the polymer blend was increased due to the increase in charge carrier mobility according to model of the free-volume. The ε′ and ε″ increase with increasing of filler content at low frequency only due to polarization effects. The ion hopping mechanism and the conductivity relaxation process have been investigated via utilizing the electrical modulus analysis.

Structural properties and electrical conductivity mechanisms of semiconducting quaternary nanocomposites: Effect of two transition metal oxides

Several quaternary nanocomposites, doped with two transition metal oxides, of the generalised composition formula 0.4ZnO–0.1P2O5–0.5[xV2O5–(1-x) MoO3] were prepared via the melt quenching process. We investigated the microstructural and conductivity properties of two ternary systems and four quaternary systems to determine the better semiconductor nanocomposite system for wider application purposes. The X-ray diffraction results showed the presence of superposed nanocrystallites within amorphous networks or matrices. Analysis of ultraviolet–visible absorption spectra showed that optical bandgap energy (Eopt) values varied with V2O5 concentration, and there was an inverse relationship between Eopt and average nanocrystallite size. The responsible mechanisms of ac conductivity were examined using the model of Jonscher's universal power-law and Almond–West formalism, and it was found that ac conductivity increased as temperature rose, exhibiting semiconducting features. All the ternary (two examples) and quaternary (four examples) nanocomposite systems established non-linearity in dc conductivity, caused by the small polaron hopping process with dissimilar activation energies at different temperature regions. The power-law exponent (s) of Jonscher's universal power-law revealed that the ac conductivity mechanism could be described by correlated barrier-hopping (CBH) or non-overlapping small polaron tunnelling (NSPT) models for different samples due to major structural alterations. We applied modified CBH and NSPT models (as s > 0.8) to get realistic values of different fitting parameters, and in this process, we also obtained the values of ideal or hypothetical glass transition temperature from the theoretical models. The different activation energies associated with ac conductivity and for the small polaron migration process diminished with an increment in conductivity. Scaled ac conductivity spectra demonstrated that the conductivity relaxation process relied upon the composite structural features and did not depend on temperature. These materials can be used for such applications as gas sensors, even at higher temperatures due to their semiconducting nature and the different valence states of transition metal ions.

Effect of lanthanum content on the conduction behaviors and relaxation processes of lead lanthanum zirconate titanate antiferroelectric ceramics

(Pb1-xLax) (Zr0.92Ti0.08)1-x/4O3 (PLZT x/92/8, x = 3, 5 and 7 at%) ceramics with compositions near the antiferroelectric (AFE)-ferroelectric (FE) phase boundary were fabricated by a solid-state reaction method. The effect of lanthanum content on the conduction behaviors and relaxation processes has been investigated. It was verified that the main phase with orthorhombic structure was formed in all compositions. The increase of lanthanum substitution resulted in an enhancement of diffuse phase transition. Impedance analysis suggested that the ac conductivity decreased with increasing lanthanum content. Moreover, thermally stimulated depolarization current study was utilized to establish the correlation between defect structures and relaxation processes. It showed three peaks with distinct characteristics, which originated from dipole orientation, oxygen vacancy migration and phase transition respectively. The oxygen vacancy-related defects induced by lanthanum doping were mainly responsible for the variation of conduction behaviors and relaxation processes.

Investigation of Optical Properties and Electrical Conductivity Mechanism of Fe <sub>2</sub>O <sub>3</sub>–Sm <sub>2</sub>O <sub>3</sub>–ZnO–P <sub>2</sub>O <sub>5</sub> Quaternary Glass Nanocomposite Systems

The influence of incorporation of Fe2O3 on the physical, structural, optical, and electrical properties of zinc- samarium- phosphate glasses synthesized via conventional melt quenching technique have been studied. The polycrystalline nature, crystallinity percentage, and average size of the developed nanocrystallites in the prepared sample have been determined from the obtained X-ray diffraction data. Density and molar volume data show inverse relation, which has been explained by the formation of Non-bridging oxygens. The optical bandgap energy (Eopt) values, obtained from spectroscopic data, and the calculated Urbach energy values (EU) has an inverse relationship varying with Fe2O3 concentration (x). The Fe2O3 concentration (x) dependent refractive index, electronic polarizability, molar refraction, oxide ion polarizability, optical basicity, and electronegativity have been determined. Mott's variable range hopping model is used to explain the DC conduction mechanism of the glass nanocomposites system, while the non-overlapping small polaron tunneling model has been used to explain the AC conduction mechanism. Both the AC and DC conductivity are found to increase with the incorporation of Fe2O3. The scaling property of AC conductivity reveals that the conductivity relaxation process depends on the structural composition of the present sample but is independent of temperature.

Physical properties and conductivity relaxation processes in sodium sulfo-borophosphate glasses

Many physical properties of a sodium-borophosphate glass system (BPSx) having the starting composition (30H3BO3 + xNa2SO4 + (60 − 2x) NaH2PO4 + 10ZnO) were detremined. It was found that the glass density ρ, the transition temperature Tg, and the optical gap energy decrease whereas the molar volume and Urbach ▵E energy increases with the substitution of Na2O by Na2SO4.The analysis of the evolution of the complex dielectric permittivity ε* and the complex electric modulus M* with temperature and composition of the glass indicates that the dielectric loss is dominated by ionic conduction, and the relaxation processes are non-Debye type. The evolution of the Kohlrausch–Williams–Watts (KWW) exponent β, estimated from the imaginary part of the electric modulus indicates that the investigated glass behaves as an intermediate elastic system as compared to flexible and stressed rigid phase. The obtained values of the decoupling index are of the same order of magnitude as observed for fast-ion conducting glasses.From the analysis of the experimental data, we may suggest that the glass sample BPS4 is the more thermally stable and has the highest ionic conductivity since it has the highest dielectric constant favorable for the dissociation of sodium salt.

Impedance, dielectric, and magnetic properties study of La2CrMnO6 ceramics

Double perovskite La2CrMnO6 (LCrMO) ceramics was prepared using solid state reaction technique sintered at 1433 K in ambient air. Wide range impedance spectroscopy study conducted in 20 Hz – 1 MHz over 85–440 K range allowed for separation of grain bulk and grain boundary effects. Electrical features corresponded to grain bulk and grain boundary properties were investigated. The features of imaginary part of impedance indicated electrical relaxation phenomenon occurrence in LCrMO. The temperature dependence of most probable relaxation times, τZ, obtained from impedance spectra collected below 120 K were fitted using Arrhenius relation and the activation energy equal to 0.14 eV was estimated. The Kramers-Kronig transform of the dielectric permittivity enabled to distinguish relaxation process over 85–170 K temperature range. The variable range hopping of small polaron model was fitted with better accuracy to the dielectric relaxation times, τdiel, temperature dependence, which indicated occurrence of Fermi glass related to local disorder. AC and DC conductivity relaxation processes, which corresponded to grain bulk and grain boundary contributions, respectively, were discriminated. Magnetic susceptibility of LCrMO ceramics was measured over 5–300 K range. Bifurcation between zero field cooled and field cooled dependence occurred below ~120 K. Magnetization M(H) hysteresis loops were not dependent on temperature and exhibited low values of coercive field, ~108 Oe and remnant magnetization, ~6 emu g−1, over 5–200 K range. The magnetic spin glass features were deduced. We note that coupling between electric and magnetic properties was detected: anomaly around 87 K in magnetization, related to magnetic transition, is accompanied by deviation of dielectric relaxation times discerned from the VRH temperature dependence.

Investigation of microstructure and temperature and frequency dependent dielectric relaxation of Molybdenum-zinc-selenite glass nanocomposite systems

Transition metal oxide doped glass nanocomposite bulk samples of the composition xMoO3–(1-x) (0.5ZnO–0.5SeO2), for x = 0.05, 0.1, 0.2 and 0.3 weight percent, have been developed via the process of slow cooling of the melt. The dependency of dielectric properties on temperature and frequency has been studied. Using transmission electron microscopy (TEM) micrographs, the growth of nanocrystallites and their lattice fringes have been noticed and selected area electron diffraction images have as well been observed. The results of the differential scanning calorimetric (DSC) process describe the thermal property of these compositions. The dielectric constant (ε/) and dielectric loss (ε//) value increases with the increment in temperature and reduces as frequency increases considerably. The dynamic conductivity relaxation process is non-Debye type as Kohlrausch stretching exponent (β) value is not equal to unity and obtained relaxation time shows Arrhenius behavior. The scaled electric okmodulus (complex) spectra discloses that the dynamic conductivity relaxation process depends on the composition but does not depend on temperature.

Dielectric spectroscopic study of solutions of amino silicone oil in the polar solvent mixtures of methyl ethyl ketone and methyl iso butyl ketone

The complex permittivity, complex modulus, alternating current electrical conductivity and complex impedance of the ternary mixtures of amino silicone oil in methyl ethyl ketone and methyl iso butyl ketone have been investigated at 303.15 K temperature over the frequency regime 200 Hz to 2 MHz. Complex permittivity and complex impedance data have been fitted to the Coelho model and Nyquist plot respectively. The Coelho model of complex permittivity data provides the electrode polarization relaxation time related to electric double layer relaxation processes. Nyquist plot of complex impedance data exhibits Debye type dispersion corresponding to conduction relaxation processes and electric double layer relaxation processes. Electrode polarization relaxation time (τEP), relaxation time (τEP′), ionic conductivity relaxation time (τσ), geometric relaxation time (τg) and double layer relaxation time (τdl) have been calculated using the different formalism. Static permittivity (ε0), DC conductivity (σdc) and refractive index (nD) have also been determined for all the ternary mixtures. Solvent effect interaction in amino silicone oil with methyl ethyl ketone, methyl iso butyl ketone and with their mixtures is also discussed in the paper. Systematic variation is observed in all the parameters with change in concentration of amino silicone oil in methyl ethyl ketone and methyl iso butyl ketone.

Preparation and Composition Optimization of PEO:MC Polymer Blend Films to Enhance Electrical Conductivity.

The polymer blend technique was used to improve amorphous phases of a semicrystalline polymer. A series of solid polymer blend films based on polyethylene oxide (PEO) and methylcellulose (MC) were prepared using the solution cast technique. X-ray diffraction (XRD), Polarized optical microscope (POM), Fourier transform infrared (FTIR) and electrical impedance spectroscopy (EIS) were used to characterize the prepared blend films. The XRD and POM studies indicated that all polymer blend films are semicrystalline in nature, and the lowest degree of crystallinity was obtained for PEO:MC polymer blend film with a weight ratio of 60:40. The FTIR spectroscopy was used to identify the chemical structure of samples and examine the interactions between chains of the two polymers. The interaction between PEO and MC is evidenced from the shift of infrared absorption bands. The DC conductivity of the films at different temperatures revealed that the highest conductivity 6.55 × 10−9 S/cm at ambient temperature was achieved for the blend sample with the lowest degree of crystallinity and reach to 26.67 × 10−6 S/cm at 373 K. The conductivity relaxation process and the charge transport through the hopping mechanism have been explained by electric modulus analysis. The imaginary part of electrical modulus M″ shows an asymmetrical peak, suggesting a temperature-dependent non-Debye relaxation for the PEO:MC polymer blend system.

Microscopic length scale of charge transport and structural properties of cobalt doped Ni–Zn ferrite nanocrystals: A structure property correlation study

Cobalt doped Ni–Zn ferrite nanoparticle (NZFC) were synthesized via citrate auto-ignition method to investigate the structural correlations with microscopic length scale of charge transport in system. Impedance spectroscopy revealed that both grain and grain boundary have combined effect on the conductivity relaxation process. Temperature dependent dc conductivity showed Arrhenius behavior for both grain interiors and grain boundaries. Dielectric relaxation mechanism has been elucidated via Harviliak-Negami (H.N.) formalism. Two characteristic length scales i.e. mean square displacement and spatial extent of the charge carriers inside the system were calculated via standard methods. Microstructural parameters such as bond length, bond angles, bond valence sums (BVS) etc. were estimated by Rietveld refinement of the X-Ray Diffraction (XRD) data. Changes in microstructural parameters followed the same trend as the characteristic length scales with the variation of doping content. Optimum transport properties were observed for 10 mol % of doping which were correlated with electron density plotting and BVS of different samples.

Structural characterization and electrical conductivity analysis of MoO3–SeO2–ZnO semiconducting glass nanocomposites

A series of glass nanocomposite samples of the general composition formula xMoO3–(1-x) (0.5SeO2–0.5ZnO) for x = 0.05, 0.1, 0.2, and 0.3 have been prepared by solid-state reaction, i.e., slow cooling process. The structural characteristics have been explored by analyzing X-ray diffraction patterns, Fourier-transform infrared, and UV–Vis spectra. The superposition of different nanophases SeO2, SeO3, ZnO, MoO3, Zn (SeO3), Zn (SeO4), Zn(MoO4), Zn2Mo3O8 and ZnMo8O10 over the amorphous glassy matrices have been identified, and their crystallite sizes have been evaluated as well. Fourier transform infrared (FTIR) spectra reveal different types of bonding like Zn–O–Se type and stretching vibrations of MoO6 octahedral units. It is observed that with increasing MoO3 concentration, the estimated values of optical bandgap energy, Urbach energy, and average crystallite size reduce. The dependency of electrical conductivity on frequency and temperature have been analyzed using Almond-West formalism and Jonscher's universal power-law. The non-linear character of DC conductivity and different activation energies at low and high-temperature regions affirm that the present glassy systems exhibit semiconducting nature. Moreover, DC conduction process is due to small polaron hopping through localized or defect states. The decreasing trend of power-law exponent (s) with temperature rise reveals that AC conduction mechanism is consistent with the correlated barrier-hopping (CBH) model. The existing correlated barrier-hopping model has been modified to attain reasonable values of fitting parameters and to obtain theoretical values of ideal thermodynamic glass transition temperature. The AC conductivity activation energy and free energy required for small polaron migration reduce with increasing conductivity. The scaling property emphasizes that conductivity relaxation process is subjected to the structure of the composition and does not depend on temperature.

Investigation of Ac conductivity mechanism and dielectric relaxation of semiconducting neodymium-vanadate nanocomposites: temperature and frequency dependency

A few binary nanocomposite systems of the overall composition formula xV2O5–(1-x) Nd2O3 for x = 0.2, 0.4, 0.6 and 0.8 has been synthesized via the rapid cooling process. The identification of crystal morphology, lattice fringes of the nanocrystallites, and the selected area electron diffraction patterns have been carried out using the transmission electron microscopy (TEM). TEM micrographs confirm the nanocrystallite development and amorphous character of the nanocomposites. The ac conductivity has been explored in the frequency window from 42 Hz to 5 MHz and in a wide temperature range. The dependency of ac conductivity spectra on frequency and temperature obey Almond-West formalism and Jonscher’s universal power-law. With an increment in temperature, ac conductivity increases, indicating semiconducting behavior. The power-law exponent (s) values are less than unity and increase in relation to the temperature, suggesting non-overlapping small polaron tunneling (NSPT) is the relevant ac conductivity mechanism. The reducing nature of the ac conductivity activation energy, the activation energy for polaron migration and tunneling distance are responsible for the rising of ac conductivity. The increment in the density of defect states within the mobility gap makes ac conductivity to rise as well. The scaled spectra of ac conductivity prove that conductivity relaxation process is temperature independent but composition dependent. In the electrical conduction process, only 66%–71% of the total charge carriers are involved. The values of dielectric constant (ε/) and dielectric loss (ε//) increase with temperature rise and drop with a rise in frequency. The coinciding scaled complex electric modulus spectra (M/ and M//) point out that the dynamical relaxation mechanism is a non-Debye type and is independent of temperature but depend on composition.

Lithium ion conductivity in Li2O–P2O5–ZnO glass-ceramics

A series of new glass-ceramic samples containing Li2O has been prepared to explore their electrical transport properties. XRD patterns of them reveal the formation of different types of nanocrystallites, dispersed in amorphous glassy matrices. Study of dc conductivity (σdc) of them shows their thermally activated nature. Formation of more non-bridging oxygen in the compositions may enhance their ionic conductivity. Conductivity spectra at various temperatures have been studied and interpreted using Jonscher's universal power-law and Almond-West formalism to shed some light on transport mechanism. The frequency independent conductivity (plateau region) in low-frequency zone is caused by diffusion of Li+ ions. Moreover, in the high-frequency dispersive region, the conductivity is because of correlated and pseudo-three-dimensional motion of Li+ ions in percolating networks. In consequence, the power-law exponent values become greater than 1 and exhibit super-linear and/or NCL (nearly constant loss) nature. Correlated barrier hopping (CBH) model is modified to some extent, which yields a better fit to experimental results. Here, ion hopping and characteristic relaxation times have been correlated with electrical conductivity with good precision. The master curve in conductivity scaling analysis reveals that conductivity relaxation process in the present system are independent of temperature as well as composition.

Electrical properties of lithium bromide poly ethylene oxide / poly vinyl pyrrolidone polymer blend elctrolyte

The development of Lithium batteries has gained more attention nowadays. polyethylene oxide (PEO)/Polyvinyl pyrrolidone (PVP) based Solid polymer electrolytes (SPEs) was prepared with lithium bromide by solution casting technique. From the X-ray diffraction studies, the amorphous nature of the polymer blend with the inclusion of LiBr had been studied. FT-IR study was used to find the presence of functional groups and the complex formation between the bonding of polymers. The maximum ionic conductivity was found to be 1.59 × 10−6 S/cm for PEO (30 wt %)/PVP (70 wt %)/Lithium bromide (4 wt %) at 303 K within the frequency range of 42 Hz - 1 MHz. The dielectric response of the SPE systems was studied at the temperature range of 303–363 K. An important factor of ion conduction is the relaxation behavior of polymer chains which was clarified by the dielectric properties of the SPE systems. Further, the capability of the polymer to dissolve salt was determined by the dielectric constant (ε). At lower frequencies, the higher dielectric permittivity was attained due to deposit of ionic charges. The ionic movement enhances the dielectric loss and dielectric permittivity. The conductivity relaxation process and the ion hopping mechanism have been explained by using the Electric modulus analysis.

Dielectric and electrical behaviour over the static permittivity frequency regime, the refractive indices and viscosities of PC–PEG binary mixtures

The complex permittivity, alternating current electrical conductivity, electric modulus and the impedance dispersion over the frequency range from 20Hz to 1MHz for the propylene carbonate (PC) and poly(ethylene glycol) (PEG; molecular weight 200gmol−1) mixtures spanning the entire mixing range have been investigated. The Nyquist plots of electric modulus and impedance for these polar liquid mixtures exhibit the Debye–type dispersion corresponding to the conductivity and electric double layers relaxation processes, respectively. The values of static permittivity, dc electrical conductivity, refractive index and viscosity of the PC–PEG mixtures in the temperature range 5–55°C have been reported. The excess properties of static permittivity, refractive index, and viscosity confirm the hydrogen-bond interactions between the PC and PEG molecules in their mixtures. The temperature dependent dc conductivity and viscosity of the PC–PEG mixtures obey the Arrhenius behaviour, and the activation energies of the mixtures decrease with an increase of PC concentration. The Stokes-Einstein relation for the conductivity in viscous media holds only for the PC-rich of PC–PEG mixtures.

Dielectric studies on PVP-CH3COONa based solid polymer electrolytes

Solid polymer electrolytes have been prepared with different wt% compositional ratios of PVP-CH3COONa by solution cast technique. The ionic conductivity of the prepared solid polymer electrolytes has been measured by the Nyquist plots and the higher ionic conductivity was found to be 2.12x10-5 S/cm at room temperature for the composition 80PVP:20CH3COONa. Dielectric studies were performed on the prepared polymer films at room temperature in the frequency ranging between 5000 Hz and 50000 KHz to find the best optimum conductivity and electric relaxation process of the samples.

Frequency and temperature dependent conductivity spectra of mixed transition metal oxide doped semiconducting glassy system

Frequency and temperature dependent conductivity of mixed transition metal oxide (TMO) doped semiconducting glassy system, xV2O5–(1−x) (0.05MoO3–0.95ZnO) have been investigated in the wide range of frequency and temperature. The dc conductivity (σdc), crossover frequency (ωH), frequency exponent (n) and power law exponent (s) have been computed from the best fitted plots of experimental data. We have estimated the values of activation energy of ac conduction (Eac) and free energy of polaron migration (EH). Dc conductivity of the as-prepared samples shows thermally activated non–linear nature, which has been interpreted with Vogel–Tammann–Fulcher (VTF) model. From the fitting, pseudo activation energy (Ea) and thermodynamic ideal glass transition temperature (T0) have been estimated. Nature of variation of conductivity and the power law exponent (s) data exhibit that non–overlapping small polaron tunnelling (NSPT) model is suitable to interpret these data for compositions x=0.3, 0.5 and 0.7. On the other hand, correlated barrier hopping (CBH) model is most applicable mechanism for ac conduction for compositions x=0.9 and 0.93. Formation of some complex Mo-O-V structures may be possible reason for applicability of CBH model for composition x=0.9, 0.93. It is also observed that conductivity relaxation process of charge carriers (polarons) is independent of temperature, but depends upon composition.

Electric modulus, scaling and ac conductivity of La2CuMnO6 double perovskite

A sample of La2CuMnO6 (LCM) was synthesized through the standard solid state reaction method. X-ray diffraction experiments and Rietveld analysis reveal that the material crystallizes in an orthorhombic structure. SEM image displayed well-defined regular shaped nearly spherical and unequal grains with grain-size lies between 2.5 and 3.0 μm ranges. Frequency dependence of dielectric, electric modulus and ac conductivity of LCM has been studied as a function of both frequency and temperatures. The conduction mechanism is explained using universal power law (σ (ω, T) = B ωn(T)). The Kohlrausch–Williams–Watts (KWW) model approaches were employed to fit frequency response curves of M′ and M″. The large asymmetry of M″(f) peaks were explained by stretched exponent parameter (β). Activation energy values suggest that the conduction mechanism and relaxation process have a different origin. The ε′ and ε″, as a function of normalized frequency, exhibit better master curves than M″ vs M′ data.

High performance of La, Nd multi-rare earth doped Na0.46Li0.04Bi2.5Nb2O9 high temperature piezoceramics at a new pseudo-MPB

Aurivillius type Na0.46-xLi0.04Bi0.5-x(LaNd)x/2Bi2Nb2O9 ceramics were prepared by a conventional solid state sintering method. The evolution of crystal structure, microstructure and corresponding electrical properties were studied. A new pseudo morphotropic phase boundary between orthorhombic to pseudo-tetragonal phases was identified near x∼0.06, giving rise to the enhancement of piezoelectric properties. The resonance and antiresonance impedance modulus at rising temperatures demonstrated that the ceramics with 6 mol% La3+/Nd3+ doping (NLN-6) was indeed piezoelectric in nature at 700°C. The electrochemical impedance spectra indicated that thermally excited intrinsic oxygen vacancies were responsible for both electrical conduction and dielectric relaxation processes. The NLN-6 ceramics exhibited superior electrical properties (d33∼20.1 pC/N, kp∼6%,TC∼737°C, ρ ∼1MΩ·cm@600°C) and also possessed excellent stability of piezoelectric properties with rising temperature. These results suggest that La3+/Nd3+ multi- rare-earth ions modified Na0.46Li0.04Bi2.5Nb2O9 ceramics are promising candidates for ultra-high temperature piezoelectric applications.