Dielectric Properties Of Ceramics Research Articles

Origin of the ultrahigh field-induced strain in the Gd-doped 0.854Bi0.5Na0.5TiO3-0.12Bi0.5K0.5TiO3-0.026BaTiO3 ternary ceramic system

This study focused on analyzing the ferroelectric, piezoelectric, and dielectric properties of lead-free Bi0.487Na0.427K0.06Ba0.026TiO3 (0.854BNT-0.12BKT-0.026BT) ternary ceramic system by systematically doping 0.001, 0.01, 0.1, 0.5, and 1.0 mol% Gd2O3. The specific composition that was investigated is located at the tetragonal side of the rhombohedral-tetragonal morphotropic phase boundary (MPB) region. Undoped and Gd-doped BNT-BKT-BT ceramics were produced by the conventional solid-state reaction method. Ferroelectric, piezoelectric, and dielectric properties of ceramics were analyzed by carrying out electrical measurements from sintered samples. An ultrahigh field-induced unipolar strain of 0.52% at 65 kV cm−1, with a converse piezoelectric coefficient d33* of up to 795 pm V−1, was achieved with 0.5 mol% Gd doping. This was attributed to the Gd dopant disrupting the normal ferroelectric order and leading to the formation of a nonpolar relaxor phase. The field-induced transition from the nonpolar relaxor phase to the normal ferroelectric phase resulted in relatively large field-induced strain values in the 0.5 mol% Gd-doped ceramics. These results suggest that Gd-doped BNT-BKT-BT ceramics hold promise for digital actuator applications.

A novel high hardness and low loss Mg5Ga2Sn2O12 ceramic with spinel-structure

Inorganic oxides with a spinel structure play an indispensable role in various applications because of their stability and exceptional performance. This study prepared Mg5Ga2Sn2O12 ceramics using the solid-state method. TEM analysis reveals that the ceramics show local lattice distortions. When the sintering temperature is 1480 °C, the relative density and Vickers hardness of Mg5Ga2Sn2O12 ceramics are 96.8 % and 12.58 GPa, respectively. The Mg5Ga2Sn2O12 ceramics exhibit optimum microwave dielectric properties, with εr = 8.57, Q × f = 138,769 GHz, and τf = −24.7 ppm/°C. Far-infrared fitting shows that the vibration mode in the low-wave number region has a significant influence on the dielectric properties of ceramics. The P–V−L theory indicates that the Sn–O bond has the most significant influence on εr and Q × f. Given these advantages, Mg5Ga2Sn2O12 ceramics hold promise for applications in low-loss dielectric materials.

Excellent piezoelectric response and low dielectric loss of PIN-PHT ceramics obtained through synergy of defect engineering and localized heterostructure

Pb-based piezoelectric ceramics with excellent piezoelectric response and low dielectric loss are crucial for advanced applications but still challenging to achieve. Herein, an approach based on synergistic effect of defect engineering and localized heterogeneous structures was developed to prepare 0.11 Pb(In0.5Nb0.5)O3-0.89 Pb(Hf0.47Ti0.53)O3+xmol%(Sb5++Nd3+) advanced piezoelectric ceramics by solid phase reaction method. Effects of ion co-doping on physical phase structures, defect concentrations, and electric domain morphologies of ceramics were all investigated. A mapping relationship between defect concentration, formation of localized heterogeneous structure, and modulation of piezoelectric and dielectric properties of ceramics was extracted. Values of d33, TC, εr, tanδ (%), and kp of ceramics obtained at x = 0.4 mol% were determined as respectively 607 pC/N, 313.1°C, 3407.81, 1.42, and 0.66, showing excellent overall performances. The doping of (Sb5++Nd3+) skillfully modulated the concentration of defects inside ceramics, resulting in excellent piezoelectric response and reduced dielectric loss. On the other hand, lattice distortion induced by doping generated nanodomains formed localized heterostructures and significantly reduced the Gibbs free-energy barrier, resulting in excellent piezoelectric response and dielectric properties. These effects can mainly be attributed to synergistic action of defect engineering and localized heterostructures. Overall, proposed ceramics and strategy look promising for preparing Pb-based piezoelectric ceramics with excellent comprehensive performance.

Microstructure and microwave‐absorbing properties of B4C/C composite powders produced by combustion synthesis with an AC foaming agent

AbstractTo develop microwave‐absorbing properties of dielectric ceramics, B4C/C composite powders were prepared by combustion synthesis with B2O3, polyvinyl alcohol, and Mg as the raw materials in this work. The XRD, Raman, scanning electron microscope with energy‐dispersive spectroscopy, and VNA network analysis carried out the effects of the addition of azodicarbonamide (AC) foaming agent on the phase compositions, microstructure, and dielectric and microwave‐absorbing properties of the products. The results indicated that the addition of an AC foaming agent contributed to the formation of distinct morphologies with a larger specific surface area and uniform distribution of the free carbon in the B4C/C composite powders and improved its graphitization degree, which resulted in the formation of equivalent microcapacitors, enhanced interfacial polarization, improved conductive network, and leading to a low reflection loss (RL) and a broadened effective absorb bandwidth (EAB). Due to the dielectric loss as the dominant loss mechanism, C‐1.5 (1.5 wt.% AC foaming agent addition) exhibits the EAB of 3.02 GHz and the minimum RL (RLmin) of −22.90 dB at the thickness of 2.20 mm.

Non-stoichiometry influence on dielectric properties of CaCu3Ti4O12 based ceramics

CaCu3Ti4O12 (CCTO) based ceramics with variations in the amount of CuO and TiO2 were prepared using powders synthesized via the coprecipitation method and calcined in two stages. The ceramics, denoted as CaCuxTiyO12, where 2.70 ≤ x ≤ 3.00 and 3.25 ≤ y ≤ 4.00 (CCxTyO), were sintered using conventional method at 1150 °C for 2 h. The evaluation of the structure, microstructure, and semiquantitative microanalyses of the CCxTyO ceramics was conducted. Impedance spectroscopy, over the frequency range of 20.0 Hz to 5.0 MHz, was performed to analyze the dielectric constant (εr′), dielectric loss factor (tanδ), impedance (Z*) and electrical modulus (M*) of the ceramics. The correlation between the variations in the amounts of CuO and TiO2, microstructure, and dielectric properties of ceramics was explored. It was observed that stoichiometric variation of the amounts of CuO and TiO2 could significantly impact in the grain growth, phase content, and consequently in dielectric properties of the ceramics. Among the ceramics studied, the CC2.90T3.75O ceramic exhibited the largest amount of CaCu3Ti4O12 (98.4%) and D50 (8.38 µm), the highest dielectric constant (εr′ = 26,880) and the lower tanδ (0.063) at 1 kHz.

STUDY OF THE INFLUENCE OF VARIATIONS IN THE PHASE COMPOSITION ON THE DIELECTRIC PROPERTIES OF FERROELECTRIC CaTiO<sub>3</sub> CERAMICS DOPED WITH Y<sub>2</sub>O<sub>3</sub>

The study of the relationship between the effect of phase composition variation on the dielectric characteristics of ferroelectric ceramics is one of the most important fundamental questions, the answer to which will allow us to determine the potential of using ferroelectrics in microelectronic applications and the creation of alternative energy sources (solid oxide fuel cells). The purpose of this study is to explore the effect of the Y2O3 dopant on the phase formation processes and the properties of the synthesized ferroelectric ceramics of calcium titanate, as well as to establish the connection between the influence of the formation of impurity phases on the change in the dielectric properties of ceramics. According to the data of X-ray phase analysis, it was found that the addition of Y2O3 with a concentration above 0.15 M leads to the formation of an orthorhombic CaY2O4 phase in the ceramic structure, the weight contribution of which increases with the dopant concentration growth. An analysis of the dependence of the specific electrical conductivity (σDC) with varying dopant concentration showed that the maximum value of σDC is achieved at dopant concentrations of 0.05 M, which leads to structural ordering due to the effect of adding yttrium oxide acting as a stabilizer, as well as the formation of impurity donor conductivity in the structure. An analysis of the dependence of the specific electrical conductivity (σDC) from dopant concentration was carried out. It has been established that the maximum value of σDC is achieved at a dopant concentration of 0.05 M. This is explained by structural ordering due to the addition of a stabilizer – yttrium oxide, as well as the formation of impurity donor conductivity in the synthesized sample. At the same time, the established dependences of the change in dielectric characteristics are in good agreement with the change in the phase composition, and an increase in the concentration of charge carriers due to the introduction of a donor impurity in the form of Y3+ leads to the appearance of volume-charge polarization in ceramics.

Effect of M (M = Mn or Mg) ion doping on microstructure and dielectric properties of Ba4Nd9.33Ti17.5-xSn0.5MxO54 ceramics prepared by sol-gel method

The changing trends of Ba4Nd9.33Ti17.5-xSn0.5MxO54 (BNST-xM) ceramic dielectric properties and microstructure were investigated by substituting two types of metal ions M (M = Mn, Mg) for Ti4+ at B-site. X-ray diffractometer (XRD) results show that M2+ are successfully formed as a single tungsten-bronze type structured phase, except that x is equal to 1.25. It can be seen from the scanning electron microscope (SEM) that the rise of the ion doping amount gradually increases the defects, and the crystal shape gradually changes from slender columnar to short and rounded. M2+ substitutions greatly impacted the suppression of oxygen vacancies and Ti3+ generation in BNST-xM ceramic, particularly Mg2+, which was confirmed by X-ray photoelectron spectrometer (XPS) results. The incorporation of M2+ ions into the system increased the Q·f value while reducing the dielectric constant of the ceramics. Mg2+ can improve the material's Q·f value, and the doping of Mn2+ will lessen the frequency temperature coefficient of the material more. When the doping amount x of Mg2+ was 0.25, the system had the best dielectric properties: ε = 64.4, Q·f value = 10,170 GHz, and τ = 25 ppm/°C.

Structure characteristics and enhanced microwave dielectric properties of Ba(Mg1/3Nb2/3)O3–Mg2SiO4 composite ceramics with a tunable τf

The performance of microwave communication devices widely used in 5G network is strongly determined by the properties of dielectric ceramics used in the fabrication, which are required to have a suitable dielectric constant (εr), high Q × f value and near-zero temperature coefficient of resonant frequency (τf). In this work, (1-x)Ba(Mg1/3Nb2/3)O3–xMg2SiO4 (x = 0.1, 0.2, 0.3, 0.4, 0.5) composite ceramics meeting the application requirements have been developed and investigated. Ba(Mg1/3Nb2/3)O3 and Mg2SiO4 could coexist without any unexpected phases due to the different crystal structures and coordination relationship. The sintering behavior and the structural changes of Ba(Mg1/3Nb2/3)O3 were specifically relevant to the microwave dielectric properties. Introducing appropriate Mg2SiO4 content promoted the sintering of Ba(Mg1/3Nb2/3)O3 and the maximum Q × f value of 110,000 GHz was obtained at the sample with x = 0.3 sintered at the optimized temperature of 1420 °C. Due to the low dielectric loss and the opposite sign τf value of Mg2SiO4, the composite ceramic successfully adjusted the τf value to near zero while maintaining a high Q × f value. However, the experimentally measured values of εr and τf were significantly different from the theoretically calculated values due to the “rattling” effect of B-site cations and the enhanced symmetry of oxygen octahedra in Ba(Mg1/3Nb2/3)O3. These structural changes were confirmed by the results of bond valence analysis and Raman vibration spectra. The 0.6Ba(Mg1/3Nb2/3)O3–0.4Mg2SiO4 ceramic sintered at 1420 °C exhibits competitive microwave dielectric properties: εr = 18.9, Q × f = 91,000 GHz (at 8.016 GHz) and τf = 2.6 ppm/°C, which indicates it a promising application prospect of microwave communication.

Effect of oxygen vacancy on the dielectric relaxation characteristics of PMNT ceramics

The as-sintered 0.68 Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 ceramics were firstly prepared using the Columbite technique and then further annealed in specific atmosphere. The effect of annealing atmospheres, e.g. O2, N2 and air conditions, on the phase structure, microstructure and dielectric properties of ceramics were systematically discussed. The obtained results suggested that, compared to as-sintered sample, there is no obvious difference in phase structure and microstructure for ceramics annealed in O2 atmosphere, showing pure perovskite structure and higher density. While the appearance of second pyrochlore phase and porosity can be found as sample was annealed in nitrogen or air condition. It is worth noting that the dielectric properties of ceramics are very sensitive to the annealing atmosphere and there is a significant increase in dielectric constant and decrease in dielectric loss as the PMNT ceramic was treated in O2 atmosphere, while sample annealed in N2 or air condition would show the opposite trend.

Influence of the firing temperature on the dielectric properties of ceramics based on barium titanate

The object of the research is the firing temperature of ceramic materials based on barium titanate. In laboratory conditions, barium titanate was synthesized from raw materials of barium carbonate and titanium dioxide using ceramic technology, taking into account the stoichiometric composition of the compound. In order to study the effect of the firing temperature on the properties of the ceramic material, three temperatures were selected: 1270, 1300, and 1350 °C. The physical properties of the samples (imaginary density, water absorption, open porosity) were determined by the method of hydrostatic weighing in water. The samples were saturated with water after their preliminary evacuation. The dielectric characteristics of the obtained materials were measured on an E7-8CLR automated device (Ukraine) at a frequency of 1 kHz. The structural and morphological features of ceramics based on synthesized barium titanate were investigated by direct scanning electron microscopy and X-ray phase analysis. On the basis of the complex of studies carried out, the technological parameters of the production of ceramics were selected. Thus, the duration of grinding at the first and second stages is 10 and 30 minutes; moisture content of the press powder – 8 %; pressing pressure – 20 MPa; temperature of the first firing – 1000 °С; temperature of the second firing – 1350 °C. The regularity of the change in the dielectric constant on the firing temperature of ceramics based on barium titanate was established. The investigated samples, obtained according to the given technological regime, are characterized by the following indicators: dielectric constant – 259.9; open porosity – 0.02 %; water absorption – 0.01 %; imaginary density – 5.45 g/cm3. The resulting material can be used to create composite ceramic materials that protect biological and technical objects from the effects of electromagnetic radiation, and can also be used to create new functional materials for space, aerospace, electronic engineering and medicine.

Effects of piezoelectric and dielectric properties of (Bi0.5Na0.5) TiO3-Ba (Ti, Zr) O3ceramics

Lead-free piezoelectric ceramics Zr and Mn-doped Ba (ZrxTi1-x) O3-0.5 mol% MnO2 (BZT100x-Mn, x=0.04, 0.045, 0.05, 0.055, 0.06 and 0.065) have been fabricated by the conventional solid-state reaction technique. The effects of Zr on the microstructure and electrical properties of the samples have been studied. The results revealed that the specimens exhibit the perovskite structure and a small amount of MnO2 can improve effectively the densification and electrical insulation of the ceramics. Because of high densification, good electrical insulation the donor-and acceptor-doping effects of MnO2, the piezoelectric and dielectric properties of ceramics are improved considerably. The ceramics shows an excellent piezoelectric strain constant d33 as 213 pC/N. A distinct positive temperature coefficient of resistance (PTCR) effect over a wide temperature range has been observed in all samples. With the addition of 0.5 mol% MnO2, the sample Ba(ZrxTi1-x)O3-0.5 mol% MnO2 with x=0.06 (BZT6-Mn) ceramics display low ρ values of 103 Ω cm at room temperature and their abrupt changes of 102-103 near Curie Temperature.

Comparative study of synthesis method on dielectric properties of ceramics of binary composition 0.6PMN–0.4PZN

It is demonstrated that the dielectric properties of ceramics in the 0.6PMN–0.4PZN system have been studied as a function of different synthesis method at various temperatures. A detail and systematic study of phase, grain size and dielectric properties has been carried out by using X-ray diffraction, SEM techniques and dielectric measurement. Our analysis revealed that the optimum results were obtained for ceramics synthesized by columbite method as compared to combustion. The maximum dielectric constant was found to be 25,300 with Tc 46 °C at 100 Hz by columbite method whereas 17,449 with Tc 43 °C at 100 Hz by combustion method. The article concludes with the brief discussion of promising method with acceptable relaxor behavior.

Significantly improved dielectric properties of TiO2 ceramics through acceptor-doping and Ar/H2 annealing

The acceptor-doped rutile TiO2 ceramics, x mol% M2O3-(1-x) mol% TiO2 (M = Al3+, Ga3+, and In3+), were prepared by solid state reaction method. The influence of Ar/H2 annealing on the structural and dielectric properties of the ceramics were systematically investigated. Our results reveal that the dielectric properties of the ceramics can be significantly improved by the Ar/H2 annealing. Ga3+ is found to be the most suitable dopant with the best doping level of 5 mol%. Excellent dielectric properties of colossal and flat dielectric permittivity (~1.2 × 105 (@1 kHz and 25 °C), low dielectric loss (~0.1), and good frequency stability were achieved over the temperature range of -70–150 °C in the Ar/H2-annealed 5 mol% Ga2O3-95 mol% TiO2 ceramic. This approach of acceptor-doping and Ar/H2 annealing leads to two thermally activated relaxations in the sample. The low-temperature relaxation is argued to be a Maxwell-Wagner relaxation caused by frozen electrons, while the high-temperature relaxation is a glass-transition-like relaxation associated with the freezing process of the electrons. This work highlights that engineering low-temperature Maxwell-Wagner relaxation paves a new way other than the frequently used acceptor-donor dual doping to design superior dielectric properties in the TiO2 system.

Crossover from Ferroelectric to Relaxor Behavior in Ba1-xCaxTiO3 (x = 0.17) System.

The dielectric properties of Ba1−xCaxTiO3 (x = 0.17) ceramics were studied in a wide frequency range of 20 Hz–53 GHz. Diffused ferroelectric phase transition was revealed close to 339 K in the dielectric properties of ceramics. The behaviour of distributions of relaxation times in vicinity of the ferroelectric phase transition temperature is also typical for order-disorder ferroelectric phase transition. However, at lower temperatures (below 200 K), the most probable relaxation increased according to the Arrhenius law. At lower temperatures the maximum of the imaginary part of dielectric permittivity versus temperature strongly shifted to higher temperatures when the frequency increased (from 125 K at 1.21 kHz to 300 K at 33 GHz). This behaviour was attributed to the dynamics of Ti ions. The origin of the crossover from ferroelectric to relaxor behaviour of Ba1−xCaxTiO3 (x = 0.17) ceramics is discussed in the paper.

Direct ink writing of continuous SiO2 fiber reinforced wave-transparent ceramics

This article reports the first example of 3D printed continuous SiO2 fiber reinforced wave-transparent ceramic composites via an adaptation of direct ink writing technology to improve the mechanical and dielectric properties of ceramics. The ceramic inks showed good printability by adding nano-SiO2 powder. The effective continuous fiber-reinforced printing progress was achieved through the design and optimization of the coaxial needle structures by finite element simulation. After printing, the continuous fibers were evenly and continuously distributed in the matrix ceramics and the high molding precision for fiber reinforced composite was kept. It is demonstrated that 10 vol% continuous SiO2 fiber improved the bending strength of ceramics by about 27% better than that of the ceramics without fiber and the dielectric performance has also been greatly improved. The novel method unravels the potential of direct ink writing of continuous fiber reinforced wave-transparent ceramics with complex structures and improved properties.

Sinterability and Dielectric Properties of LiTaO3-Based Ceramics with Addition of CoO.

Lithium tantalite (LiTaO3) is a common piezoelectric and ferroelectric crystal, but the LiTaO3 polycrystalline ceramics have rarely been reported, and their refractory character presents difficulties in their fabrication. In this study, LiTaO3-based ceramics with different amounts of CoO were prepared by pressureless sintering at 1250 °C, and the effects of the amount of sintering aid on the sinterability, microstructure, and dielectric properties of the ceramics were investigated. The relative densities of the LiTaO3-based ceramics were significantly improved by the addition of CoO powder. The LiTaO3-based ceramics achieved the highest relative density (89.4%) and obtained a well-grained microstructure when the added amount of CoO was 5 wt.%. Only the LiTaO3 phase in the ceramics was observed, indicating that the ions Co diffused into the LiTaO3 lattices and mainly existed in two forms: Co2+ and Co3+. The effects of the added amount of CoO on the dielectric properties of the LiTaO3-based ceramics were studied thoroughly. Consequently, the dielectric constant was enhanced, and the dielectric loss decreased in the LiTaO3-based ceramics with the addition of CoO. The optimal value was obtained at 5 wt.% of CoO-added LiTaO3-based ceramics.

Raman, EPR and structural studies of novel CuZrNb2O8 ceramic for LTCC applications

Abstract To determine the mechanism of microwave response in AZrNb2O8 (A: Mn, Zn, Mg, Co, et al.) wolframites, CuZrNb2O8 ceramic with low sintering temperature (920 °C) is successfully fabricated by solid-state reaction method. Meanwhile, its structural stability is synthetically evaluated, the vibration modes are also calibrated. Except for the extrinsic factor like sintering temperature, the condition of Jahn-Teller ion Cu2+ as intrinsic part is characterized for the first time in relation to the microwave dielectric properties of the system. In virtue of Raman and EPR spectra, it is predicted that the electronic structure of transition metal ions, as the less concerned factor, may be influential on the dielectric properties of ceramics at microwave range, especially in the structure with mixed ion occupancy. In addition, the CuZrNb2O8 ceramic is well matched with the silver electrode, which makes it a prospective candidate for temperature compensation material of LTCC (low-temperature co-fired ceramic) passive integration technology.

Relaxation Effects in Nonstoichiometric NBT-Based Ceramics

Effects of cation nonstoichiomtry on crystal structure parameters, microstructure, and dielectric properties of ceramics (Na0.5+xBi0.5)TiO3and (Na0.5-xBi0.5)TiO3with Bi/Na<1 and of solid solutions [(Na0.5Bi0.5)1-xKx]TiO3and (Na0.5Bi0.5)(Ti1-xMgx)O3withx= 0 – 0.1 have been studied. Changes in the unit cell parameters and microstructure of the samples observed in ceramics prepared correlate well with both preparation conditions and radii of substituting cations. Ferroelectric phase transitions near ~ 400 K and ~ 600 K were confirmed ib the systems studied. Phase transitions near ~ 400 K demonstrate a pronounced relaxor behavior determined by the presence of polar regions in a nonpolar matrix. Besides, additional anomalies related to presence of relaxing dipoles formed by oxygen vacancies were observed on temperature dependences of dielectric permittivity at temperatures higher than 700 K. The results obtained confirmed that increase in nonstoichiometry lead to increase in ionic conductivity of the samples.

Influence of synthesis method on dielectric properties of ceramics of ternary composition PMN-PT-PZN

The influence of different synthesis methods on structure formation, crystallographic aspects, and dielectric properties of PMN-PZN-PT relaxor ferroelectric ceramics were examined. Single-phase perovskite 0.7PMN-0.2PT-0.1PZN ceramics were synthesized at different sintering temperature (1100–1170 °C) by the columbite (M-I) and combustion (M-II) method. Ceramics synthesised were characterised by XRD and SEM to confirm the phase and particle size. Ceramics of composition 0.7PMN-0.2PT-0.1PZN demonstrated relatively lesser grain size and density in columbite method than combustion method. Correlations between the crystal structure, grain size and dielectric properties were established. The Ɛr max values for M-I were 16557–28328 and for M-II were 20145–25865 in the sintering temperature range 1150–1170 °C respectively.

Impact of quenched random fields on the ferroelectric-to-relaxor crossover in the solid solution (1−x)BaTiO3−xDyFeO3

Lead-based perovskite relaxor ferroelectrics are widely used as materials for numerous applications due to their extraordinary dielectric, piezoelectric, and electrostrictive properties. While the mechanisms of relaxor behavior are disputable, the importance of quenched (static) random electric fields created at nanoscale by the disordered heterovalent cations has been well recognized. Meanwhile, an increasing amount of scientific and technological efforts has been concentrated on lead-free perovskites, in particular, solid solutions of classical ferroelectric $\mathrm{BaTi}{\mathrm{O}}_{3}$ (BT), which better meet ecological requirements. Among BT-based solutions the homovalent systems are elaborately studied where strong random electric fields are absent, while the solubility limit of heterovalent solutions is typically too low to fully reveal the peculiarities of relaxor behavior. In this paper, we prepare a perovskite solid solution system $(1\ensuremath{-}x)\mathrm{B}{\mathrm{a}}^{2+}\mathrm{T}{\mathrm{i}}^{4+}{\mathrm{O}}_{3}\ensuremath{-}x\mathrm{D}{\mathrm{y}}^{3+}\mathrm{F}{\mathrm{e}}^{3+}{\mathrm{O}}_{3}$ ($0\ensuremath{\le}x\ensuremath{\le}0.3$) and study it as a model heterovalent lead-free system. We determine crystal structure, ferroelectric, and dielectric properties of ceramics in a wide range of temperatures and concentrations, construct a phase diagram, and find and analyze the concentration-induced crossover from normal ferroelectric to relaxor behavior. We demonstrate that quenched random electric fields of moderate strength promote the ferroelectric-to-relaxor crossover, but do not change qualitatively the peculiarities of relaxor behavior, while strong enough fields destroy the relaxor state, so that the material becomes an ordinary linear dielectric. The experimental results are compared with the predictions of known theories of relaxor ferroelectricity.