Structural, Dielectric and Electrical Properties of Lead Zirconate Titanate and CaCu3Ti4O12 Ceramic Composite (original) (raw)
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Ceramics with high dielectric permittivity are of intense interest due to their enabling role in the mini-aturization of electronic devices. In particular, lithium niobate (LiNbO 3), due to its remarkable pyroelec-trical, piezoelectrical and photorefractive properties, is an important material for a large variety of technological applications. Lithium ferrite (LiFe 5 O 8) is another very interesting ferromagnetic material due to its square hysteresis loop, high Curie temperature. It is of technology importance as a low-cost substitute of garnet ferrites in several devices. In this work we present the studies on the composite material with LiNbO 3 and LiFe 5 O 8 here described by (x) LiFe 5 O 8 À(100Àx) LiNbO 3 with x = 0, 25, 50, 75 and 100 (wt%). The structure and the dielectric properties of the samples, processed in a domestic microwave oven and by the conventional solid state method, are discussed. The influence of thermal treatment time and temperature was investigated.
Structural and dielectric characterization of LiNbO 3 nano-size powders obtained by Pechini method
Lithium niobate is an artificially synthesized material with wide technological applications, due to its numerous physical properties, such as: ferroelectricity, birefringence and large pyroelectric, piezoelectric, non-linear, acousto-optic, electro-optic and photo-elastic coefficients. It also exhibits very strong bulk photovoltaic and photo refractive effects. In the present work, LiNbO 3 powders were prepared by the Pechini (sol–gel) method. The heat-treatment of the base amorphous powders, at 450 °C promotes the formation of LiNbO 3 crystalline phase. The electrical characterization, in function of the heat-treatment time, shows that the dc conductivity depends on the quantity of crystalline phase, which increases with the increase of heat-treatment time. The sample treated for 96 h shows a dielectric constant value of *35, at low frequencies. A dielectric relaxation phenomenon independent of the temperature of measurement was detected in the samples treated at 48 and 96 h, shifting to higher frequencies with the increase of the heat-treatment time.
2008
Abstract High density sodium lithium niobate lead free ceramics near the morphtropic phase boundary [Na x Li 1− x NbO 3,(LNN), x= 0.12] were prepared by the solid state reaction method. XRD patterns showed that the lattice structures were changed after polarization. The temperature dependence of the dielectric constant and dielectric loss, pyroelectric coefficient and DSC curves of LNN ceramics showed that there exist three phase transitions from room temperature up to the Curie temperature.
Journal of Advanced Dielectrics, 2017
Polycrystalline perovskite structured (Li[Formula: see text] (Na[Formula: see text] K[Formula: see text])[Formula: see text] (Nb[Formula: see text]Ta[Formula: see text] Sb[Formula: see text] O3 ceramics with [Formula: see text], 0.005 and 0.01 mole excess Na concentration were prepared by solid state sintering method. The present study relates the role of excess Na addition with the stoichiometry, density, structure, dielectric and ferroelectric properties of the samples. X-ray diffraction (XRD) pattern exhibits single phase orthorhombic structure. The characteristic Raman modes were observed due to translational modes of cations and vibrational modes of NbO6 octahedra and no structural phase transition were observed. This confirms the formation of single phase perovskite structure and is consistent with XRD results. The dielectric permittivity increases about two times, while dielectric loss decreases by four times for [Formula: see text] composition. The electrical measurements ca...
Dielectric properties of ceramics in lead zirconate titanate-lead magnesium niobate system
Songklanakarin J Sci Tech, 2004
Yimnirun, R., Ananta, S. and Laoratakul, P. Dielectric properties of ceramics in lead zirconate titanate -lead magnesium niobate system Songklanakarin J. Sci. Technol., 2004, 26(4) : 529-536 In this study, the xPb(Zr 0.52 Ti 0.48 )O 3 -(1-x)Pb(Mg 1/3 Nb 2/3 )O 3 (when x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1.0) ceramic composites are prepared from PZT and PMN powders by a conventional mixed-oxide method. The dielectric properties of the ceramics are measured as functions of both temperature (-150 -400ºC) and frequency (100 Hz -1 MHz). The results indicate that the dielectric properties of the pure phase PZT and PMN are of normal and relaxor ferroelectric behaviors, respectively. The dielectric behaviors of the 0.9PZT -0.1PMN and 0.7PZT -0.3PMN ceramics are more of normal ferroelectrics, while the other compositions are obviously of relaxor ferroelectrics. In addition, the transition temperature decreases and the maximum dielectric constant increases with increasing PMN content in the system. These results clearly show the significance of PMN in controlling the dielectric behavior of the PZT-PMN system.
Journal of the European Ceramic Society, 2006
Mixed ionic and electronic conductors of La 1−x Ca x FeO 3−δ (LCF, x =0.0-0.5) have been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), dilatometry, and four-probe electrical conductivity measurements. Ca substitution on La site reduces the LaFeO 3 sinterability and the cell volume of this orthorhombic crystal. Dense samples for property studies can be sintered at 1320 • C. Nevertheless, the sintering temperature is near the decomposition temperature of LCF for those solid solutions of x ≥ 0.3. The LCF decomposition is evident when a La-poor secondary phase, not detected in XRD, was revealed in SEM micrographs of 1270 • C thermally etched samples of x ≥ 0.3. Dilatometric studies demonstrate linear increments in thermal expansion with increasing temperature in samples of x ≤ 0.2, while show strange bendings in thermal expansion curves of x = 0.4 and 0.5. The bending in thermal expansion indicates influences of the secondary phase. The TEC value of compositions of x ≤ 0.2 is between 10.8 and 11.7 × 10 −6 • C −1 . The LCF electrical conductivity increases with the Ca content and its temperature dependence can be described by the small polaron hopping mechanism. The composition around x = 0.15 promises to be a superior cathode for SOFC since it thermally matches with 8 mol% YSZ and 10 mol% Dy, Er substituted LAMOX electrolytes and possesses electrical conductivity near 90 S cm −1 at 800 • C.
Dielectric properties of Na 1− x Li x NbO 3 ceramics from powders obtained by chemical synthesis
Ceramics International, 1999
Ultra-®ne powders of Na 1Àx Li x NbO 3 (x=0; 0.06; 0.09; 0.12 ) were synthesized by the Polymeric Precursors Method. Such powders had their orthorhombic structures determined by X-ray diraction and their surface area determined by BET isotherms (less than 10 m 2 g À1 ). Densi®cation was followed by dilatometric study. The powders, calcined at 700 C for 5 h, were sintered at 1290 C during 2 h under ambient atmosphere with no application of extra pressure. The samples with relative densities higher than 95% were analyzed by impedance spectroscopy at room temperature, under a signal amplitude of 1 V rms . Dielectric constants of about 180 and dielectric loss factor of about 0.03 were measured showing small dependence with frequency. The electrical properties were similar to those obtained for samples sintered by hot pressing. #
Dielectric properties of Na 1Àx Li x NbO 3 ceramics from powders obtained by chemical synthesis
Ultra-®ne powders of Na 1Àx Li x NbO 3 (x=0; 0.06; 0.09; 0.12) were synthesized by the Polymeric Precursors Method. Such powders had their orthorhombic structures determined by X-ray diraction and their surface area determined by BET isotherms (less than 10 m 2 g À1). Densi®cation was followed by dilatometric study. The powders, calcined at 700 C for 5 h, were sintered at 1290 C during 2 h under ambient atmosphere with no application of extra pressure. The samples with relative densities higher than 95% were analyzed by impedance spectroscopy at room temperature, under a signal amplitude of 1 V rms. Dielectric constants of about 180 and dielectric loss factor of about 0.03 were measured showing small dependence with frequency. The electrical properties were similar to those obtained for samples sintered by hot pressing. # 1999 Elsevier Science Limited and Techna S.r.l. All rights reserved
2010
A new tungsten bronze ceramic oxide, Pb 2-x K 1+x LixNb 5 O 15 (PKLN) (x =0.15) was prepared by high temperature solid-state reaction route. Structural and electrical properties are investigated using X-ray diffraction and dielectric measurements. Room temperature XRD pattern confirms the formation of the compound with an orthorhombic crystal system. The dielectric permittivity and the loss tangent of the sample have been measured in a frequency range 1Hz-1MHz and a temperature range 35-550 °C. Studies of dielectric properties show that the compound exhibits an anomaly at 425°C (usually called transition temperature).The electrical parameters of the material were studied using complex impedance spectroscopy showing that the compound exhibits non-Debye of relaxation process. In the paraelectric phase, activation energy was determined and the value is Eτ = 0.68 eV. The present ceramic is promising candidate for high dielectric constant and low loss dielectric ceramic.
Journal of Materials Science, 2011
This article describes the processing and characterisation of lanthanum-doped lead zirconate titanate (PLZT)-based ferroelectric fibres for composite transducer applications. X-ray diffraction of the extruded and sintered fibres indicated some lead loss during sintering; however, the fibres exhibited low porosity (1.54%), high maximum piezoelectric strain (4041 ppm) and relatively low coercive field (0.77 kV/mm). The low coercive field of the lanthanum-doped fibres may be advantageous in terms of facilitating polarization of the fibres in composite architectures.