Structural and electrical properties of Na2Pb2Eu2W2Ti4X4O30 (X=Nb, Ta) ferroelectric ceramics (original) (raw)

Structural and electrical properties of a new lead free tungsten bronze ferroelectric ceramics Na2Ba2Eu2W2Ti4Nb4O30

Journal of Materials Science: Materials in Electronics, 2016

Lead free polycrystalline sample of Na 2 Ba 2 Eu 2 W 2 Ti 4 Nb 4 O 30 was prepared using high-temperature (*1200°C) solid-state reaction technique. Room temperature X-ray structural analysis confirms the formation of single phase compound in orthorhombic crystal structure. The surface morphology of the sintered sample recorded by scanning electron microscope exhibits a uniform grain distribution. The compositional characterization of the sample was carried out using energy dispersive spectroscopy. Detailed studies of the nature of variation of dielectric constant and tangent loss with temperature indicate possible existence of ferroelectricity in the material. The temperature dependence of electrical parameters (impedance, modulus, etc.) of the material exhibits a strong correlation of its microstructure (i.e., bulk, grain boundary, etc.) with the electrical parameters. The hopping mechanism for electrical transport properties of the system with non-exponential type of conductivity relaxation was suggested on the basis of electrical modulus analysis. The frequency dependence of ac conductivity suggests that the material obeys Jonscher's universal power law. The temperature dependence of dc conductivity of the compound follows Arrhenius equation. Ferroelectric property of the compound was confirmed from polarization (hysteresis) study.

Electrical properties of Na2Pb2R2W2Ti4V4O30 (R = Dy, Pr) ceramics

Journal of Advanced Ceramics, 2013

The polycrystalline samples of complex tungsten bronze (TB) Na 2 Pb 2 R 2 W 2 Ti 4 V 4 O 30 (R=Dy, Pr) compounds were prepared by solid-state reaction technique. Room-temperature preliminary structural studies confirm the formation of the compounds in the orthorhombic crystal system. Detailed studies of electrical properties of the materials using complex impedance spectroscopy technique exhibit that the impedance and related parameters are strongly dependent upon temperature and microstructure (bulk, grain boundary, etc). An observation of negative temperature coefficient of resistance (NTCR) suggests the materials have semiconducting properties. The variation of AC conductivity with temperature shows a typical Arrhenius behavior of the materials. Both the samples obey Jonscher's universal power law. The existence of hopping mechanism in the electrical transport processes in the system with non-exponential type of conductivity relaxation is confirmed by electrical modulus analysis.

Ferroelectric Properties of Na 2 Pb 2 R 2 W 2 Ti 4 V 4 O 30 (R = Dy, Pr) Ceramics

Research Letters in Materials Science, 2007

The polycrystalline samples ofNa2Pb2R2W2Ti4V4O30(R = Dy, Pr) were prepared by low-temperature, (i.e., at650∘C) solid-state reaction technique. The preparation conditions have been optimized using thermogravimetry analysis (TGA) technique. X-ray diffraction (XRD) studies of the compounds showed the formation of a single-phase orthorhombic crystal structure at room temperature. Studies of dielectric properties (ɛrand tanδ) of the compounds at frequencies 10, 100, and 1000 kHz in a wide temperature range (room temperature–500∘C) exhibit ferroelectric phase transitions at132∘Cfor NPDWTV and at122∘Cfor NPPWTV of diffuse type. Ferroelectric properties of the materials are confirmed by polarization study.

Electrical properties of complex tungsten bronze ferroelectrics; Na2Pb2R2W2Ti4V4O30 (R= Gd, Eu)

amlett.com

Complex impedance analysis of new tungsten bronze ferroelectric vanadates, Na 2 Pb 2 R 2 W 2 Ti 4 V 4 O 30 (R = Gd, Eu), was carried out on samples prepared relatively at low temperature using a mixed-oxide technique. The formation of the materials under the reported conditions has been confirmed by an X-ray diffraction technique. A preliminary structural analysis exhibits orthorhombic crystal structure of the materials at room temperature. The electrical properties of the materials have been studied using ac impedance spectroscopy technique. Detailed studies of impedance and related parameters exhibit that the electrical properties of the materials are strongly dependent on temperature, and bear a good correlation with their microstructures. The temperature dependence of electrical relaxation phenomenon in the materials has been observed. The bulk resistance, evaluated from complex impedance spectra, is found to decrease with rise in temperature, exhibiting a typical negative temperature coefficient of resistance (NTCR)type behavior similar to that of semiconductors. A small contribution of grain boundary effect was also observed. The complex electric modulus analysis indicates the possibility of hopping conduction mechanism in the system with non-exponential type of conductivity relaxation. The ac conductivity spectra exhibit a typical signature of an ionic conducting system, and are found to obey Jonscher's universal power law.

Dielectric and electrical properties of Na2Pb2La2W2Ti4Ta4O30 electroceramics

Journal of Advanced Ceramics, 2012

The polycrystalline sample of complex tungsten-bronze type compound (Na 2 Pb 2 La 2 W 2 Ti 4 Ta 4 O 30) was prepared by a high-temperature solid-state reaction technique. Room temperature preliminary structural study using X-ray diffraction (XRD) data exhibits the formation of a single-phase new compound. The SEM micrograph of the compound exhibits non uniform rectangular grains distributed throughout the sample surface. Detailed studies of dielectric parameters (ε r , tan δ) as a function of temperature and frequency, and P-E hysteresis (spontaneous polarization) confirmed the existence of ferroelectricity in the material. Complex impedance spectroscopy analysis, carried out as a function of frequency at different temperatures, established a correlation between the microstructure and electrical properties of the material. The electrical relaxation process occurring in the material is temperature dependent. The activation energy found from the Arrhenius plot that the conduction process in the material is of mixed type. The nature of frequency dependence of ac conductivity suggests that the material obeys Jonscher's universal power law.

Dielectric and electrical properties of a tungsten bronze tantalate ceramic

Current Applied Physics, 2013

Using high temperature solid state reaction the polycrystalline sample of K 2 Pb 2 Dy 2 W 2 Ti 4 Ta 4 O 30 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 C.

Structural, dielectric and electrical properties of CaBa4SmTi3Nb7O30 ferroelectric ceramic

Bulletin of Materials Science, 2011

The polycrystalline sample of CaBa 4 SmTi 3 Nb 7 O 30 , a member of tungsten bronze family, was prepared by solid-state reaction method. X-ray diffraction analysis shows the formation of single-phase compound with an orthorhombic structure at room temperature. Scanning electron micrograph of the material shows uniform distribution of grains. Detailed studies of dielectric properties of the compound as a function of temperature at different frequencies suggest that the compound has a dielectric anomaly of ferroelectric to paraelectric type at 198°C, and exhibits non-relaxor kind of diffuse phase transition. The ferroelectric nature of the compound has been confirmed by recording polarization-electric field hysteresis loop. Piezoelectric and pyroelectric studies of the compound have been discussed in this paper. Electrical properties of the material have been analyzed using complex impedance technique. The Nyquist plots manifest the contribution of grain boundaries (at higher temperature), in addition to granular contribution (at all temperatures) to the overall impedance. The temperature dependence of dc conductivity suggests that the compound has negative temperature coefficient of resistance (NTCR) behaviour. The frequency dependence of ac conductivity is found to obey Jonscher's universal power law. The observed properties have been compared with calcium free Ba 5 SmTi 3 Nb 7 O 30 compound.

Synthesis, Structural, Electrical, and Thermal Studies of Pb1−𝑥Ba𝑥Nb𝟐O𝟔 (𝑥=𝟎.𝟎 and 𝟎.𝟒) Ferroelectric Ceramics

ISRN Ceramics, 2012

The polycrystalline ceramic samples of lead barium niobate with general formula ( and 0.4) were prepared by conventional solid state reaction method. The room temperature X-ray diffraction patterns reveal that both of the samples have orthorhombic crystal structure with space group Cm2m. The dielectric constant and dissipation factor were measured as a function of frequency (100 Hz-2 MHz) and temperature (RT-660K). The DC electrical conductivity of both the samples was measured from RT to 660 K. The activation energies calculated from logσversus 1000/Tcurves in ferroelectric phase of the compounds are 1.09 eV for pure () sample and 1.36 eV for Ba-substituted () sample. The values of activation energies show that the substitution of Ba2+ion on Pb2+ion site increases the resistivity of pure PbNb2O6() ceramic. The modulated differential scanning calorimetry (MDSC) has been used to investigate the phase transition temperature of both the compounds and also to see the effect of Ba2+ion s...

Structural, electrical and dielectric properties of Na2W3O10 ceramic

Materials Letters, 2003

Polycrystalline samples of Na 2 W 3 O 10 are prepared by a solid-state reaction technique. Preliminary X-ray powder diffraction studies of the compound suggest the formation of single-phase material in the triclinic crystal system. Measurement of dielectric constant (e) and tangent loss (tand) as a function of temperature have shown dielectric anomaly at T c = 258 jC, suggesting the transition to be of the first order. Variation of dc conductivity with temperature shows that the conductivity of the material is temperature dependent and increases with the increase in temperature. D

Dielectric and Ferroelectric Characterization of Na(Ta,Nb)O3 Solid Solution Ceramics

Journal of Electroceramics, 2005

Ceramics in the Na(Ta 1−x Nb x)O 3 system were prepared by a solid state reaction approach, and their dielectric characteristics were evaluated together with the structures. The complete solid solution with orthorhombic structures was observed in the present system, and three supposed phase transitions at about 475, 580 and 650 • C were observed by DTA. Only one dielectric anomaly was observed at high temperature for x = 0.2 and 0.4, and alternative dielectric anomaly (a diffused dielectric peak) was observed around 170 and 380 • C for x = 0.6 and 0.8, respectively. The compositions of 0.6 and 0.8 are weakly ferroelectric and those of 0.2 and 0.4 are supposed to be antiferroelectric at room temperature.