Dielectric Properties Of Solid Solutions Research Articles

Peculiarities of the dependences of the dielectric properties of solid solutions of multicomponent systems on the electronegativity of their constituent cations

Solid solutions (SS) of 3- and 4-component systems based on lead titanate-zirconate were prepared by the method of solid-phase reactions and uniaxial hot pressing. The dependences of the relative permittivity of polarized samples on the electronegativity (EN) of their constituent cations have been studied. The ferro-hardness of the SS (the stability of the domain structure to external influences) is shown to be directly dependent on the EN of elements B in the corresponding oxidation states, i.e., the degree of covalence of the B–O bond. The deviation from this dependence in SS with Ni and Cd is explained by their individual features, which result in changes in the degree of bond covalence in both cationic sublattices. The conducted crystal-chemical analysis made it possible to choose promising SS when creating ferroelectric materials, including textured piezoelectric ceramic materials for piezoelectric transducers for various purposes: Piezotransformers, piezoelectric motors, ultrasonic emitters, filter devices, ultrasonic flaw detectors, accelerometers, etc.

Structure and properties of solid solutions in BiFeO3-based system

This paper presents a study of microstructure and dielectric properties of solid solutions of (1-х)BiFeO3 − x/2 PbFe1/2Nb1/2O3 − x/2 PbFe2/3W1/3O3 system with x = 0.05 ÷ 0.50 using X-ray diffraction analysis. Phase diagram of the studied system at room temperature is obtained. Critical influence of oxygen defects and liquid phase on formation of structure and microstructure of the samples is detected. Relaxor nature ε′′/ε0 for the studied solid solutions is demonstrated dealing with occurrence of Maxwell-Wagner’s relaxation due to movement of oxygen vacancies.

Point Defects of Bismuth in TlInTe2 Crystals: Electrophysical and Dielectric Properties of Solid Solutions

Point Defects of Bismuth in TlInTe2 Crystals: Electrophysical and Dielectric Properties of Solid Solutions

Dielectric properties of solid solutions in a PFN-based system

The results of X-ray diffraction analysis of the solid solutions in the (1-x)Pb(Fe1/2Nb1/2)O3–xPb(Fe2/3W1/3)O3 systems with x = 0.0÷0.5, investigating their microstructure and measurements of dielectric characteristics are presented in this paper. The critical influence of Pb(Fe2/3Wy1/3)O3 on the crystallization of solid solutions and the nature of grain boundaries is established. A sintering mechanism of the solid solutions is defined. Correlations between the dynamics of the crystalline and grain structures and the dielectric properties of investigating solid solutions are established.

Effects of modification of bismuth ferrite with small-sized rare earth elements

The phase and grain structures and the dielectric properties of solid solutions (SS) of bismuth ferrite modified with small-sized rare-earth elements (SRE) are studied. The regularities of the appearance of impurities of various compositions depending on the ion radius and SRE concentration in objects are revealed. Based on the analysis of the dielectric spectra of the SSs, the development of Maxwell-Wagner relaxation associated with the accumulation of fSRE charges at the interfaces between the components was established in them. The conclusion is made about the possibility of using the results obtained when creating a new generation of multifunctional materials.

Synthesis, X-ray Diffraction Characterization, Mössbauer Spectroscopy, and Dielectric Properties of Solid Solutions in the PbFe2/3W1/3O3–PbSc2/3W1/3O3 System

Ceramic Pb(Fe1–xSc x )2/3W1/3O3 samples with 0 ≤ x ≤ 1 have been prepared and characterized by X-ray diffraction, Mossbauer spectroscopy, and dielectric and pyroelectric measurements. The stoichiometry ranges of the perovskite solid solutions in this system have been identified, their structural parameters have been determined, and their dielectric permittivity, dielectric loss tangent, resistivity, and thermally stimulated depolarization current have been measured as functions of temperature. The composition dependences of the dielectric properties for the solid solutions have been obtained. The solid solutions have been shown to exhibit ferroelectric relaxor properties, with a well-defined maximum in their permittivity in the range 180–250 K.

Phase Pattern of Barium Strontium Titanate System and Dielectric Responses of Its Solid Solutions

Samples of solid solutions of the system Ba1–x Sr x TiO3 (0 ≤ x ≤1.0) are produced by solid-phase synthesis followed by sintering using conventional ceramic technology. Their crystal structure and grain structure are studied at room temperature and dielectric properties – in a wide range of external influences (temperature and frequency of the alternating electric field). Based on these results, the state diagram of the system is constructed including three single-phase fields with different-symmetry (tetragonal, pseudocubic, and cubic) and two morphotropic fields with coexistence of the tetragonal and pseudocubic, pseudocubic and cubic phases. Peculiarities of the grain landscape associated with the formation of morphotropic areas and melting of barium hydroxide are revealed. The dependence of the dielectric properties of solid solutions on their crystal-chemical specifics and position in the phase diagram of the system is demonstrated. A conclusion is made about the possibility of using the compositions with x = 0.2 to create materials with high dielectric constants promising for applications in microelectronics.

Phase states and dielectric properties of solid solutions of (1–х)NaNbO3–xSr2Nb2O7, (1–х)NaNbO3–xCa2Nb2O7 binary systems

Solid solutions of (1–х)NaNbO3–xSr2(Ca2)Nb2O7 (0 ≤ x ≤ 0.2, Δx = 0.025) binary systems are fabricated via solid-phase reactions with subsequent sintering using standard ceramic technology. Patterns in the formation of their crystalline structure and dielectric properties are established in a wide interval of temperatures and frequencies.

Structural, magnetic, and dielectric properties of solid solutions between BiMnO3 and YMnO3

Bi1−xYxMnO3 (0.1≤x≤0.9) solid solutions were prepared by the high-pressure high-temperature method at 6GPa and 1573K. They crystallize in the GdFeO3-type perovskite structure with the Pnma symmetry. Crystal structures of Bi0.9Y0.1MnO3 and Bi0.5Y0.5MnO3 are studied by synchrotron X-ray powder diffraction at room temperature. Only one Néel temperature, TN, is found in samples with 0.1≤x≤0.9 in comparison with two Néel temperatures observed in YMnO3 (TN=29 and 39K). Samples with 0.5≤x≤0.9 have almost constant TN=44K, while TN starts to increase linearly for other compositions: TN=46K for x=0.3, TN=58K for x=0.2, and TN=68K for x=0.1. Field-induced transitions from canted-antiferromagnetic states to antiferromagnetic states are detected at about 30kOe for x=0.2 and 70kOe for x=0.1. Dielectric constant increases below TN in samples with 0.5≤x≤1, while it decreases below TN in samples with 0.1≤x≤0.3. Our data suggest that a magnetic structure changes near x=0.4. By extrapolation, we could estimate lattice parameters (a=5.9221Å, b=7.5738Å, and c=5.4157Å) and TN=79K for a hypothetical Pnma modification of BiMnO3.

Phase formation and dielectric properties of ceramics in the BiFeO3–BaTiO3–Bi(Mg0.5Ti0.5)O3 system

We have studied the effect of Bi(Mg0.5Ti0.5)O3 additions on the phase formation, structural parameters, microstructure, and dielectric properties of solid solutions in the region of a morphotropic phase boundary in the BiFeO3–BaTiO3 system. Single-phase samples with the perovskite structure have been obtained and the addition of Bi(Mg0.5Ti0.5)O3 has been shown to raise the Curie temperature of the ceramics and improve their dielectric properties.

Dielectric properties of solid solutions (1 − x)(KBi)1/2TiO3-xNa1/4Bi3/4Fe1/2Ti1/2O3 near the morphotropic phase boundary

The dielectric properties of solid solution ceramics (1 − x)(KBi)1/2TiO3-(x/2)(NaBi)1/2TiO3-(x/2)BiFeO3 near the morphotropic phase boundary lying near x = 0.75 and separating the compositions with the orthorhombic (x 0.75) structures have been studied. The solid solutions are shown to undergo a diffuse phase transition with the Curie temperature TC = 640–650 K. Based on an analysis of the frequency dependence of the imaginary component of the electric modulus in the range T > TC, it is concluded that the transition of the system of solid solutions near the morphotropic phase boundary (x = 0.75) to the dipole-ordered state is accompanied by the formation of heterophase microregions with different relaxation times of the dielectric polarization. The activation energies of the relaxation of the dielectric polarization (ΔEM) in the aforementioned temperature range and of the dc charge carriers (ΔEdc) are determined. It is found that ΔEdc stepwise increases near 570 K in going toward higher temperatures. It is shown that the behavior of the characteristics of the dielectric response of the solid solutions below 400 K corresponds to a relaxor ferroelectric. For the compositions 0.7 ≤ x ≤ 0.8, the estimated freezing temperature of dipole clusters of the relaxation state is about 240 K, and their activation energy decreases with increasing x.

HIGH THERMAL STABILITY OF MICROWAVE DIELECTRIC PROPERTIES OFCaTi1-x(Nb1/2Fe1/2)xO3CERAMICS

This paper presents a study of the structure and microwave properties of [Formula: see text] substituted into the Ti4+site of calcium titanate ceramics. The structural and dielectric properties of solid solutions in CaTi1-x( Nb1/2Fe1/2)xO3, was done. The microwave dielectric properties of solid solutions in CaTi1-x( Nb1/2Fe1/2)xO3, (CNFTOX with x = 0.1 to x = 1) is discussed. The modified CaTiO3(CTO) ceramics were prepared by a new procedure in the solid-state method. A study of the variations of the ball-milling process was done. The calcinations were done at 900°C for 3 and 5 h respectively, and the sintering at 1100°C, for 3 h. The structural property studies of the ceramics were investigated by X-ray diffraction (XRD) and Raman spectroscopy. The X-ray analysis showed that all samples have an orthorhombic structure. The refinement analysis of all samples were also duly performed and discussed. The nine scattering bands centered at 183, 227, 247, 288, 338, 470, 490 and 805 cm-1were observed. Several peaks presented a small shift as a function of the x value. All Raman spectra in the studied samples showed a small band at 805 cm-1, which is a function of the x value. The dielectric permittivity and loss at microwave frequencies (MW) were investigated. For both calcination treatments (900°C for 3 and 5 h), the dielectric permittivity decreased with a decrease of the titanium content. Dielectric permittivity values in the range of 20 to 80 were obtained. It was also observed that a higher number of balls in the milling process contribute to the increase of the εrvalues. The CNFTO has an excellent microwave property at x = 0.6, with a temperature coefficient of resonant frequency (τf) near zero (τf= 2.8 ppm/°C).

Dielectric properties of Na1 − x K x NbO3 and Na1 − x Li x NbO3 ceramics

The dielectric properties of solid solutions based on sodium potassium and sodium lithium niobates have been studied in wide ranges of temperatures (25–750°C), frequencies (25 to 106 Hz), and electric fields (up to 30 kV/cm). We have identified solid-solution regions differing in the temperature and frequency dependences of the dielectric permittivity. It is reasonable to take into account the present results in device applications where wide variations in dc bias field and frequency are needed.

Microstructural Characterization and Dielectric Properties of Barium Titanate Solid Solutions with Donor Dopants

The correlation between the sintering temperature and dielectric properties in the <TEX>$Nb^{5+}\;and\;Ta^{5+}$</TEX> doped BaTi<TEX>$O_3$</TEX> solid solutions have been investigated. The samples were sintered at temperatures ranging from 1250 to 1350 <TEX>${^{\circ}C}$</TEX> for 4 h in air. SEM, XRD and SEM/EDS techniques were used to examine the structure of the samples with particular focus on the incorporation of <TEX>$Nb^{5+}\;and\;Ta^{5+}$</TEX> ions into the BaTi<TEX>$O_3$</TEX> crystal lattice. The X-ray diffraction peaks of (111), (200) and (002) planes of BaTi<TEX>$O_3$</TEX> solid solution doped with different fractions of <TEX>$Nb^{5+}\;and\;Ta^{5+}$</TEX> were investigated. The dielectric properties were analyzed and the relationship between the properties and structure of doped BaTi<TEX>$O_3$</TEX> was established. The fine-grain and high density of the doped BaTi<TEX>$O_3$</TEX> ceramics resulted in excellent dielectric properties. The dielectric properties of this solid solutions were improved by adding a small amount of dopants. The transition temperature of the 1.0 mole% <TEX>$Ta^{5+}$</TEX> doped BaTi<TEX>$O_3$</TEX> solid solution was <TEX>$\sim$</TEX>110 <TEX>${^{\circ}C}$</TEX> with a dielectric constant of 3000 at room temperature. At temperatures above the Curie temperatures, the dielectric constant followed the Curie-Weiss law.

Dielectric properties of solid solutions in the lead zirconate titanate–barium titanate system prepared by a modified mixed-oxide method

Ceramic solid solutions within the system (1−x)Pb(Zr0.52Ti0.48)O3–xBaTiO3, where x ranged from 0.0 to 1.0, were prepared by a modified mixed-oxide method. The crystal structure, microstructure and dielectric properties of the ceramics were investigated as a function of composition via X-ray diffraction (XRD), scanning electron microscopy (SEM) and dielectric spectroscopy. While pure BT and PZT ceramics exhibited sharp phase transformation expected for normal ferroelectrics, the (1−x)PZT–xBT solid solutions showed that with increasing solute concentration (BT or PZT), the phase transformation became more diffuse. This was primarily evidenced by an increased broadness in the dielectric peak, with a maximum peak width occurring at x=0.4.

Influence of Cation Order on the Dielectric Properties of Pb(Mg1/3Nb2/3)O3–Pb(Sc1/2Nb1/2)O3 (PMN‐PSN) Relaxor Ferroelectrics

The effect of the B‐site cation chemistry and ordering on the dielectric properties of solid solutions in the (1−x)Pb(Mg1/3Nb2/3)O3–Pb(Sc1/2Nb1/2)O3 (PMN‐PSN) perovskite system was examined in samples with 0.1 ≤x≤ 0.9. Thermal annealing treatments were effective in inducing long‐range B‐site order in the samples within this compositional range. The well‐ordered, large chemical domain ceramics exhibit relaxor behavior up to x=∼0.5; for higher values of x, normal ferroelectric behavior was observed. For x≤ 0.5 reductions in the chemical domain, size had no significant effect on the weak‐field dielectric properties, but induced a transition to relaxor behavior for x &gt; ∼0.6. The disordered PSN‐rich samples undergo a spontaneous zero‐field relaxor to ferroelectric transition similar to that reported previously for PSN. The field‐dependent properties of compositions lying closest to the relaxor to ferroelectric crossover exhibited the highest sensitivity to alterations in the chemical order. The properties of this system are consistent with a “random site” description of the 1:1 ordered Pb(β′1/2β1/2)O3 structure with β′= (Mg(2−2x)/3Nb(1−x)/3Scx) and β″= Nb.

Microwave Dielectric Characteristics of Y2BaZnO5 Ceramics with Sm Substitution for Y

The effect of Sm substitution for Y in (Y2-xSmx)BaZnO5 solid solutions on the microwave dielectric properties was investigated in order to develop the new microwave dielectrics with high-Q and near zero τf values. The Q·f values were decreased from 165000 to 35500 GHz, whereas the temperature coefficient pf resonant frequency (τf) varied from -45 to -5 ppm/°C with increasing the composition x. Moreover, the dielectric constants (εr) of the samples were increased from 15.8 to 18.6; this result is attributed to the increase in the ionic polarizabilities and expansion of the R2O11 (R=Y and Sm) polyhedron caused by Sm substitution for Y. Thus, the appropriate microwave dielectric properties of solid solutions were: εr=16, Q·f=120000 GHz and τf=-32 ppm/°C for x=0.5.

Crystal Growth and Dielectric Properties of Solid Solutions of Pb(Yb1/2Nb1/2)O3–PbTiO3 with a High Curie Temperature near a Morphotropic Phase Boundary

The Pb(Yb1/2Nb1/2)O3–PbTiO3 (PYN–PT) binary system single crystal near the morphotropic phase boundary (MPB) composition with (100) planes of 1–2 mm length on one side was successfully grown by the flux method using PbO–PbF2–B2O3 flux. The PYN–PT (47/53) single crystal was found, by simultaneous microdifferential thermal analysis and thermogravimetric analysis, to show a peritectic melting point at 1205°C with a decomposition of the perovskite crystals into a pyrochlore phase and a liquidus point at 1253°C. The structure of the PYN–PT (47/53) single crystal was determined by X-ray diffraction study to be tetragonal with a=4.05±0.01 A and c=4.14±0.01 A at room temperature. The PYN–PT single crystal shows the maximum value of the relative permittivity εr of 16000 at 1 kHz at a Curie temperature Tc of 404°C, which is as high as that in the Pb(Zr, Ti)O3 system near the MPB and the value of the remanent polarization Pr of about 26 µC/cm2 at 140°C.

Piezoelectric and dielectric properties of solid solution of PbZrO 3–PbTiO 3–Pb(Mg 1/3Nb 2/3)O 3 system prepared by wet–dry combination method

Ternary perovskite-type solid solutions of Pb(Zr x Ti 1− x ) 1− y (Mg 1/3Nb 2/3) y O 3 (PZTMN) were synthesized by wet–dry combination method in which a wet-process was applied to B-site cations. These solid solutions had no compositional fluctuation and high density. Their dielectric constant and electromechanical planar coefficient ( k p) were higher than those of PZTMN prepared by the conventional dry method. Moreover, their compositional dependence of k p exhibited a peak at the morphotropic phase boundary, while PZTMN prepared by the dry method did not.

Prediction of the dielectric properties of non-ferroelectric complex perovskites and of the ternary system Ba/SrO-Ln2O3-xTiO2for microwave applications

Abstract In the first part of this work an attempt is presented to predict the dielectric properties of solid solutions of non-ferroelectric complex perovskites by means of structural predictions based on the tolerance factor and a microscopic model, an estimation of the optical permittivity based on the Gladstone-Dale relation, and an estimation of total polarisability accordingly to the molecular/ion additivity rule. The objective is to produce materials with increased relative permittivity ε0 and very low thermal coefficient of the resonant frequency τf. The new compositions with predicted dielectric properties are then fabricated in ceramic form and structurally, electrically and optically characterised to verify the model. Results show good agreement with the structural features and optical permittivities. However, the calculated total polarisability for relative permittivities larger than 20 seems to be inaccurate and need further development. In the second part, the study of the dielectric and structural properties of ceramics based on the ternary system Ba/SrO-Ln2O3-xTiO2 (Ln= Nd, Sm, Gd) with 4 < x < 5 is presented. A preliminary attempt to relate the dielectric behaviour with the structural properties and the chemical and phase composition was made in the case of Ln= Nd, Sm. Special attention was paid to the thermal coefficient of the permittivity τε, because it shows positive values for Ba-Sm-based compounds and negative values for the Ba-Nd-composition and for Ba/Sr-Sm-solid solutions.