0000000000004970
AUTHOR
M. Livinsh
The Effects of 3d Admixtures on Properties of Relaxor PLZT8/65/35 Ceramics
A study of the effects of the 3d dopants Mn, Fe, Co, Ni, and Cu on relaxor behavior and other properties of the ferroelectric PLZT8/65/35(La8) ceramic compound by X-ray diffraction, electron microscopy and other techniques is reported. The complex dielectric permittivity ϵ* = ϵ′-iϵ′′ is measured in the 20–400°C range of temperature at frequencies within the range of 102 – 106 Hz. Essential changes caused by the admixtures in the behavior of dielectric permittivity with frequency and temperature are observed along with changes in the XRD SEM patterns are observed. The mechanisms of the phenomena are discussed.
Processing, basic characterization and standard dielectric measurements on PLZTx/65/35 (4 ≤x≤ 11) ceramics
The influence of external stress (0–800 bar) on the dielectric properties of lead lanthanum zirconium titanate (PLZT) x/65/35 (4 ≤ x ≤ 11) ceramics was investigated. Applying uniaxial pressure leads to a change in the peak intensity of the electric permittivity (ϵ), in its frequency dispersion as well as in the dielectric hysteresis. The peak intensity of ϵ becomes broader and shifts to lower temperatures for PLZT x/65/35 with x = 4, 7, 9.75 and 11, with increasing pressure, on heating. It was concluded that applying uniaxial pressure induces an increase of Tm, and thus has a similar effect as the increase of the Ti ion concentration in the lead zirconium titanate (PZT) system. Results base…
Structure and Properties of Novel Pb(B’1/2Nb1/2)O3-PbTiO3 Binary Systems with High Piezoelectric Coupling
The (l-x)Pb(Lu1/2Nb1/2)O3-xPbTiO3 (PLuNT) and (l-x)Pb(Er1/2Nb1/2)O3-xPbTiO3 (PErNT) binary systems have been originally synthesized. Pure lutecium niobate (PLuN) (x = 0) has a pronounced long-range order in the B-sublattice and an antiferroelectric to paraelectric phase transition at ~258°C. The phase structure of the PLuNT system, at room temperature, changes from a pseudomonoclinic (psd-M, space group Bmm2) to tetragonal (T, space group P4mm). The pseudomonoclinic phase extends over the 0 ≤ x ≤ 0.38 interval within which the monoclinic angle β proceeds a minimum near to 90° at x≅0.2. The morphotropic region covers over the interval x = 0.38–0.49, the concentration ratio psd-M:T≅l (the mor…
Investigation of mechanical and electrical properties of Li doped sodium niobate ceramic system
ABSTRACTThe Na0.96Li0.04NbO3 ceramic solid solution was prepared by means of a two-stage hot-pressing technology. The X-ray diffraction analysis showed the formation of a single perovskite phase with an orthorhombic symmetry in the investigated composition. The microstructure and EDS measurements were performed. They confirmed the high purity and the expected qualitative composition. A good homogeneity of the microstructures and a small degree of porosity were observed. The elastic modulus (the Young's modulus E, shear modulus G, and Poisson's ratio ν) of Na0.96Li0.04NbO3 were determined with the use of an ultrasonic method. The electrical properties of Na0.96Li0.04NbO3 ceramics were invest…
SYNTHESIS AND CHARACTERIZATION OF SB-SUBSTITUTED (K0.5Na0.5)NbO3 PIEZOELECTRIC CERAMICS
ABSTRACT Lead-free piezoelectric ceramics (K0.5Na0.5)(Nb1-xSbx)O3+0.5 mol.%MnO2, where x = 0 ÷ 0.10, with single phase structure and rhombohedral symmetry at room temperature were prepared by conventional ceramic technology. The optimal sintering temperatures of compositions were within 1100°–1140°C. MnO2 functions as a sintering aid and effectively improves the densification. The samples reached density from 4.26 g/cm3 for undoped (K0.5Na0.5)NbO3 to 4.40 g/cm3 for Mn/Sb5+ co-doped ceramics. The co-effects of MnO2 doping and Sb5+ substitution lead to significant improvement in dielectric and piezoelectric properties: e at the Tc increased from 6000 (KNN) to 12400 (x = 0.04), d33 = 92 ÷ 192 …
Grain growth in Na 0.5 Bi 0.5 TiO 3 -based solid solutions
This paper discusses effects of different dopants, sintering technique and parameters on microstructure and properties of pure and Yb, Er-doped Na0.5Bi0.5TiO3 (NBT). All stoichiometric compositions follow the abnormal grain growth mechanism (AGG) and exhibit a bimodal grain size distribution. Bi over-stoichiometry, two step sintering and hot pressing are effective inhibitors of AGG. Microstructure of sintered NBT greatly influences such properties as dielectric permittivity and depolarization temperature.
Processing, basic characterization and standard dielectric measurements on PLZT x/65/35 (2≤x≤13) ceramics
ABSTRACTThe influence of external stress (0-800bar) on the dielectric properties of PLZT x/65/35 (2≤x≤13) ceramics was investigated. Applying uniaxial pressure leads to a change in the peak intensity of the electric permittivity (ϵ), of its frequency dispersion as well as in the dielectric hysteresis. The peak intensity of ϵ becomes broader and shifts to lower temperatures for PLZT x/65/35 with x = 2, 4, 6, 7, 9.75, 10, 11 and 13, with increasing pressure, on heating. It was concluded that applying uniaxial pressure induces an increase of Tm, and thus has similar effects as the increase of the Ti ion concentration in the PZT system. Results based on nanoregion switching processes under comb…
Influence of Axial Pressure on the Electrical Properties of Li0.06Na0.94NbO3 Ceramic
Lead-free ceramic Li0.06Na0.94NbO3 was synthesized using a conventional solid-state processing. The single-phase perovskite structure was identified by X-ray powder diffraction technique. The values of lattice parameters of Li0.06Na0.94NbO3 are lower than those for pure NaNbO3. The EDS analysis shows the fairly homogeneous distribution of all elements throughout the grains. An axial pressure significantly influences electric properties. With increasing pressure the peak intensity in the ϵ(T) curve decreases, the peak becomes diffused and shifts to a lower temperature. The value of tanδ increases with increasing axial pressure and its local maximum shifts towards lower temperatures.
The Structural, Microstructural, Mechanical and Dielectric Properties of the Li0.1Na0.9NbO3Ceramics
Polycrystalline samples of Li0.1Na0.9NbO3 were obtained by means of a conventional ceramic technology. The analysis of the X-ray diffraction pattern showed the formation of single perovskite phase with an orthorhombic structure at room temperature. The EDS and EPMA measurements revealed that the sample is perfectly sintered, chemically homogeneous and confirmed its high quality. Elastic constants: Youngs's modulus E, shear modulus G and Poisson ratio ν were determined using an ultrasonic method. The dielectric measurements were performed in heating and cooling processes. It was found that a Li-doping influence dielectric properties. The obtained results indicated that Li0.1Na0.9NbO3 is a pr…
INFLUENCE OF ZIRCONIUM ON STRUCTURAL, MICROSTRUCTURAL AND FERROELECTRIC PROPERTIES OF BaZr0.20Ti0.80O3 CERAMIC
ABSTRACT Barium zirconium titanate BaZrxTi1-xO3 ceramics have been obtained by conventional method. The X-ray diffraction analysis showed that the BaZr0.20Ti0.80O3 crystallizes in the cubic structure. The lattice parameter a increases with temperature, at temperature ∼308 K a small deviation is observed. The performed EDS study revealed that the samples were perfectly sintered and that the material was chemically homogeneous. It contains a little glassy phase and the grains are well shaped. The zirconium content (20 mol%) in the examined solid solution caused downward shift of the temperature T m . The increase of the achieved permittivity values ϵm was observed as well.
The Effect of Dopants on Sintering and Microstructure of Lead-free KNN Ceramics
Lead-free potassium sodium niobate (K0.5Na0.5)NbO3 (KNN) has been prepared via conventional ceramic processing method. The influence of 0.5 wt% - 1.5 wt% MnO2 and WO3 addition on the sintering, crystallographic structure, microstructure and dielectric properties of KNN has been investigated. Optimal sintering temperatures of KNN ceramics were observed to be in the narrow interval: 1090 °C - 1110 °C for MnO2 doped KNN; 1150 °C - 1170 °C for pure KNN and doped with WO3. XRD patterns showed that all the samples have single perovskite structure with monoclinic structure. Microstructure of ceramics was changed greatly by using dopants.http://dx.doi.org/10.5755/j01.ms.17.1.251
Influence of Lithium Substitution on Structure, Electric and Pyroelectric Properties of Sodium Niobate Ceramics
Li0.02Na0.98NbO3 ceramics were prepared by a conventional method. A single-phase perovskite structure was identified by an X-ray diffraction method. The SEM and EDS studies revealed that the Li0.02Na0.98NbO3 samples were perfectly sintered and chemically homogeneous. Electric measurements showed that Li0.02Na0.98NbO3 was sensitive to the frequency of the applied electric field and revealed that the ac conductivity changed with frequency according to the formula: σ(ω) = σdc +Aωn where n < 1. These results were discussed with a reference to the conduction mechanism as a type of polaron hopping.
Influence of BaTiO<inf>3</inf> on synthesis and structure of lead-free ceramics based on KNN
In the present work lead-free compositions with a stoichiometric formula (1−x)(K 0.5 Na 0.5 )Nb 1−y Sb y O 3 -xBaTiO 3 (x=0.01, 0.02, 0.04; y=0.04, 0.07) were produced by solid state sintering method. Manganese oxide MnO 2 was used as a dopant in order to lower the sintering temperatures. The influence of BaTiO 3 on the microstructure, density, mechanical and electrical properties of Sb-substituted KNN ceramics was investigated. X-ray diffraction analysis revieled pure perovskite structure. Microstructural investigation of the ceramics samples showed homogeneous structure with a slightly rounded cubical grain shape. Phase transition temperature T c is shifted to lower temperatures in compar…
Dielectric response of disordered BaBi2Nb2O9perovskite ceramics
Studies of dielectric properties of BaBi2Nb2O9 ceramics are reported. Considerable dispersion of ?* at low- and infra-low frequencies has been revealed in the region of the diffused phase transition. Dispersion of ?* is divided into ''low-temperature'' dispersion related to relaxation of polar formations and their boundaries and ''high-temperature'' dispersion (at T ? Tm) the main contribution to which comes from Maxwell-Wagner relaxation.
Microscopic Studies of YBCO-Based Polycrystalline Materials
Features of Phase Diagrams of Binary Pb(B<sub>1/2</sub>Nb<sub>1/2</sub>)O<sub>3</sub>-PbTiO<sub>3</sub> Systems in Vicinity of Morphotropic Phase Boundaries
High Electromechanical Coupling in Relaxor Pb(Sc<sub>1/2</sub>Nb<sub>1/2</sub>) O<sub>3</sub> - PbTiO<sub>3</sub> System Hot-Pressed Piezoelectric Ceramics
Relaxation of polarization in (K0.5Na0.5)(Nb0.93Sb0.07)O3 ferroelectric ceramics modified by BaTiO3
ABSTRACTA study of low-frequency relaxation of polarization in conventionally prepared ceramic compounds of (1-x)(K0.5Na0.5)(Nb0.93Sb0.07)O3+xBaTiO3+0.5mol.%MnO2 (x = 0.02, 0.04) examined over a wide temperature range is reported. Anomalous behavior of the temperature dependence of the coercive field Ec(T) is detected in the temperature range of the orthorhombic to tetragonal phase transition. The observed features of polarization are assigned to dynamics of the domain structure at the temperature range of phase coexistence.
New ferroelectric materials on the basis of PbSc1/2Nb1/2O3–PbLu1/2Nb1/2O3 solid solutions
Abstract Original binary solid solutions PbSc 1/2 Nb 1/2 O 3 –PbLu 1/2 Nb 1/2 O 3 (PSN-PLuN) have been produced. First of all nominally pure PSN and PLuN were synthesized by solid state reaction from oxides and carbonates. These compounds were mixed in different proportions to obtain (1− x )PSN− x PLuN solid solutions. Ceramic samples were hot-pressed at gradual change of the temperature. Solid solutions have the perovskite structure and are completely soluble in each other. Differential thermal analysis and X-ray diffraction were used to examine the synthesis and phase constitution. Dielectric properties—dielectric permittivity e and dielectric loss tan δ of ceramic samples of originally s…
Microscopy studies of the surface of high-temperature superconductor films
The surface morphology is studied by use of optical and electron microscopes with respect to production regime (rate and temperature of crystallization) of the 50 - 125 micrometer thick doped YBa 2 Cu 3 O 7 films obtained by Stokes sedimentation on SrTiO 3 ceramic substrate (size 20 mm by 5 mm by 0.5 mm) and firing in air or oxygen following the MTG procedure, performed in the gradient tube furnace. Evolution of thick film structure with regard to temperature and cooling rate is studied.
Morphotropic ceramic solid solutions of the Pb(B3+½Nb½)O3- PbTiO3binary system
Abstract The structure, dielectric, ferroelectric and electromechanical properties of lead lutecium niobate-titanate (PLuNT) and lead erbium niobate-titanate (PErNT) binary systems are reported. The data of phase diagram, crystallographic symmetry and morphotropic phase boundaries (MPB) are provided. High values of the electromechanical coupling coefficients kp = 0.66, kt = 0.48, k31 = 0.36 of (1−x)PLuN − xPT ceramics are attained in compositions near the MPB at x≈0.41.
Modified YBCO superconductor-ferroelectric composites: Bulk materials and thick films
Bulk samples and 50–125 μm thick films of (1-x)YBa2Cu3O7−δ-xBaTiO3 (0⩽x⩽0.12 by weight) composites have been synthesized, the films being obtained by Stokes sedimentation on SrTiO3 ceramic plates and firing in oxygen by Melt Textured Growth techniques. The phase composition and texture have been studied by X-ray diffraction and microstructure. Resistance and magnetic susceptibility of prepared samples have been measured.
PLZT—Synthesis, sintering and ceramics microstructure
Abstract Producing of PLZT powders by original two-stage co-precipitation method from mixed solution of inorganic salts ZrOCl 2 ·8H 2 O, TiCl 4 , La(NO 3 ) 3 ·6H 2 O, Pb(NO 3 ) 2 , was carried out. The sequence of phases formed during PLZT synthesis has been studied by X-ray and DTA analysis. Ceramic samples were prepared by two-stage hot-pressing technology. Dielectric, ferroelectric and optical properties have been measured. Ceramic microstructures were studied by SEM with energy dispersive analytical capability (EDX). The fine-grained microstructure was quite uniform with the average grain size of 5–7 μm, without internal or grain boundary porosity. The optical transmittance of ceramic p…
The Effect of Technological Factors on the Synthesis of PbMg 1/3 Nb 2/3 O 3
Conventional technique of solid phase reactions allows one to obtain PbMg 1/3 Nb 2/3 O 3 material with about 20 vol.% of the pyrochlore phase. The latter can be reduced to 5 vol.% by Swartz-Shrout two-stage solid state reaction via MgNb 2 O 6 having the columbite structure. A single-phase perovskite product can be obtained by by the two-stage columbite method from mixtures containing 0.2 mol. parts of overstoichiometric MgO. The best results are obtained by using magnesium carbonate hydroxide pentahydrate (MgCO 3 ) 4 ·Mg(OH) 2 ·5H 2 O as the magnesium source. The modified route yields stoichiometric single-phase PMN.
Synthesis and Characterization of Lead-Free (1-x)(K0.5Na0.5)Nb1-ySbyO3-xBaTiO3
In this study lead-free ceramics with a formula (1-x)(K0.5Na0.5)Nb1-ySbyO3-xBaTiO3 have been synthesized and studied. XRD studies showed that all compositions have perovskite structure with monoclinic or tetragonal cell depending on substitution level. KNN ceramics with BaTiO3 have more homogeneous structure and increased density in comparison with pure KNN or antimony substituted KNN. Dielectric measurements revealed diffuse phase transition.
Structure and properties of high piezoelectric coupling Pb(B′½Nb½)O3-PbTiO3binary systems
Abstract The (1-x)Pb(Lu½ Nb½)O3-xPbTiO3 and (1-x)Pb(Er½ Nb½)O3-xPbTiO3 binary systems have been obtained, the structure and properties of which are studied. The unit cell of erbium niobate (PErN) is described as pseudomonoclinic of orthorhombic Bmm2 symmetry: a=c=4.2161 A b=4.0869 A β=90.55° and composition is characterized with antiferroelectric phase transition at 305°C. The PErNT system has the morphotropic phase region extending over the x=0.4–0.6 interval. In PLuNT ceramics system the pseudomonoclinic phase structure Bmm2 extending over the 0≤x ≤0.38 interval becomes pseudocubic at x≈ 0.2. The morphotropic region is spread over 0.38< × < 0.49; at higher PT concentrations (1.0 ≥ × ≥ 0.4…
Structural and Electric Properties of Sodium Lithium Niobate Ceramic Solid Solution Li0.08Na0.92NbO3
A lead-free solid solution Li0.08Na0.92NbO3 was prepared by a two-stage hot-pressing technology. The structure and morphology of Li0.08Na0.92NbO3 were characterised by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The studies of electric conductivity were performed depending on temperature and frequency of electric measuring field on heating and cooling processes. These measurements revealed that the a.c. conductivity changed with the frequency according to the formula: σ(ω)=σ dc +Aω n where n < 1. These results were discussed considering the conduction mechanism as a type of polaron hopping.
INFLUENCE OF MONOXIDES ADDITION ON SINTERING OF SODIUM-POTASSIUM NIOBATES SOLID SOLUTION
ABSTRACT In this paper the preparation, structure and dielectric parameters of ceramics from different powders of pure potassium sodium niobate (KNN) and KNN doped with 1.0 wt% of Li2O, CdO, Bi2O3, MnO2, V2O5 and WO3 have been studied. The dopping of sintering aids did not affect the crystallographic structure of the ceramics significantly; all ceramic samples had a single-phase perovskite structure. Added elements Li2O, CdO, MnO2, V2O5 effectively decreased the sintering temperature of KNN (50°–80°C). All sintering aids influenced sinterability, microstructure and dielectric properties of ceramics. Dielectric constant for doped samples increased from 6000 up to 8000.
Effect of Electromechanical Loading on the Dielectric Properties of PLZT−x/65/35 Ceramics (x = 8 and 8.5)
The influence of uniaxial pressure (0-800 bars) applied parallel to the ac electric field on the dielectric properties of La−modified lead–zirconate−titanate ceramics with the Zr/Ti ratio of 65/35 was investigated. Applying uniaxial pressure leads to the reduction of the peak intensity of the electric permittivity (ϵ), of the frequency dispersion as well as of the dielectric hysteresis. The peak intensity of ϵ becomes diffuse and shifts with increasing the pressure. Our results show that applying uniaxial pressure induces similar effects as increasing the Ti−ion concentration in PZT system. We interpreted our results based on domain switching processes under the action of combined electrome…
SINTERING OF LEAD-FREE (K0.5Na0.5)NbO3 BASED SOLID SOLUTION
ABSTRACT In this study lead-free solid solution (K0.5Na0.5)NbO3 was prepared, structure, dielectric parameters of ceramics were investigated. The doping of sintering aids did not affect the crystallographic structure of the ceramics significantly; all ceramic samples had a single-phase perovskite structure. Added elements CdO, ZnO, MnO2, V2O5 effectively decreased the sintering temperature of KNN by 50°–80°C. All sintering aids influenced sinterability, microstructure and dielectric properties of ceramics. Dielectric constant for doped samples increased from 6000 up to 8000; Pr = 15 μC/cm2, Ec = 9 kV/cm, d33 = 110 pC/N, kp = 0.38 and Qm = 190 for MnO2 doped samples.
Dielectric properties of PLZT-x/65/35 (2 \leqslant x \leqslant 13) under mechanical stress, electric field and temperature loading
We investigated the effect of uniaxial pressure (0-1000 bars) applied parallely to the ac electric field on dielectric properties of PLZT-x/65/35 (2 \leqslant x \leqslant 13) ceramics. There was revealed a significant effect of the external stress on these properties. The application of uniaxial pressure leads to the change of the peak intensity of the electric permittivity (\varepsilon), of the frequency dispersion as well as of the dielectric hysteresis. The peak intensity $\varepsilon$ becomes diffused/sharpened and shifts to a higher/lower temperatures with increasing the pressure. It was concluded that the application of uniaxial pressure induces similar effects as increasing the Ti io…
Uniaxial Pressure Effects on the Dielectric Properties of the PLZT-x/65/35 (x = 9.75 and 10) Ceramics
The influence of uniaxial pressure (0-1000 bars) applied parallel to the ac electric field on the dielectric properties of PLZT-x/65/35 ceramics (x = 9.75 and 10) was investigated. The results show that the applied stress has a significant influence on the dielectric properties of PLZT ceramics. Applying uniaxial pressure leads to the reduction of the electric permittivity (ϵ) peak and the frequency dispersion. Moreover, the peak of ϵ becomes diffuse and shifts to a higher temperature with increasing pressure. The results show that applying uniaxial pressure induces similar effects as the increase in Ti−ion concentration in the PZT system. We interpreted our results based on the domain swit…
Influence of Uniaxial Pressure on Dielectric Properties of the PLZT-x/65/35 (x = 11 and 13) Ceramics
Uniaxial pressure (0–1000 bars) effects on the dielectric properties of the PLZT-x/65/35 ceramic samples (x = 11 and 13) samples was investigated. The obtained results reveal that the applied stress largely changes the dielectric properties of these ceramics. Applying uniaxial pressure leads to a reduction of the peak intensity of the electric permittivity and a change of the frequency dispersion. Besides with increasing the pressure the ϵ-peak shifts to a higher temperature. The results show that applying the uniaxial pressure induces similar effects as increasing the Ti−ion concentration in PZT system. These effects can be connected with the change in domain structure under the action of …
Electrical Characterization of the Fe-Doped BT Ceramics by an Impedance Spectroscopy
The electric properties of the Fe - doped BaTiO3 ceramics was investigated as a function of frequency and temperature. The structure and morphology of investigated sample were characterized by an X-ray diffraction and scanning electron microscopy. The impedance measurements were carried out at the temperature ranging from 450 K to 600 K, and at the frequency range from 0.1 Hz to 10 MHz. Based on these parameters the electrical properties of the grains and grains boundaries were described. The bulk and grains boundaries resistance of ceramics and the thermal activation energies were determined.