Dielectric dispersion near the morphotropic phase boundary of 0.64PMN-0.36PT ceramics

A near morphotropic phase boundary (MPB) composition of PMN-PT ceramic, 0.64Pb(Mg_1/3Nb_2/3)O₃-0.36PbTiO₃, has been synthesized for various piezoelectric, ferroelectric and dielectric applications. The relaxation mechanisms and dielectric characteristics of this solid solution have been investigated with dielectric spectroscopy measurements in the frequency range of 20 Hz–2 MHz. The dielectric properties have shown distinct and prominent Debye type relaxation at the temperatures corresponding to the ferroelectric phase. The peak in dielectric loss parameter has been found to be dominated by the dc conductivity in paraelectric phase. The experimentally obtained values of various parameters have been found in agreement with the values obtained by fitting of the experimental data in Debye model. An excellent agreement of the results with Debye distribution of relaxation times was obtained with the distribution parameter α showing minima around the ferro-to para-electric phase transition. Different activation energies of the relaxation time have been observed in the ferroelectric and paraelectric phases. An average relaxation time has been found to decrease from ～10^?3 s to ～10^?6 s with the increasing temperatures.     

High permittivity and low dielectric loss of the (Ca0.9Sr0.1)1-xLa2x/3Cu3Ti4O12 ceramics

In this work, we have systematically studied the effects of La³⁺/Sr²⁺ dopants on the crystal structure, microstructure, dielectric response and electrical properties of (Ca_0.9Sr_0.1)_1-xLa_2x/3Cu₃Ti₄O₁₂ (x = 0, 0.025, 0.05 and 0.075) ceramics. XRD results show that the lattice parameter increases with the increase in the La³⁺ content. SEM micrographs illustrate that a small amount added of La³⁺ can reduce the grain size of CCTO during sintering. With increasing La³⁺ content, the grains grow larger. Dielectric measurements indicated that all doped samples synthesized by the solid-state reaction exhibit giant dielectric constants ε'>10⁴ over a large frequency range (10 Hz to 1 MHz) and at any temperature below 600 K. In particular, the ceramic with x = 0.05 exhibits a colossal dielectric permittivity ～5.49 × 10⁴; which increases by about 50% compared to that of the undoped ceramic. In addition, the doped ceramic also presents a low dielectric loss ～ 0.08 at 20 °C and 0.6 kHz. The giant dielectric properties of these samples can be explained by the (IBLC) model.     

Effect of boron on crystallization,microstructure and dielectric properties of CBS glass-ceramics

Herein, we demonstrate the preparation of CBS glass-ceramics by using chemically pure CaO, SiO₂ and B₂O₃ as raw materials. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrical measurements have been carried out to explore the effect of boron addition on crystallization, microstructure and dielectric properties of CBS glass-ceramics. Furthermore, the influence of sintering temperature and sintering schemes has been systematically investigated. Results show that the increase of boron content reduces crystallization temperature of CBS glass-ceramics. For instance, with the increase of boron oxide from 10.8?wt% to 19.4?wt%, crystallization temperature decreased by 130?°C. However, excessive boron affects the precipitation of wollastonite crystal phase, destroys crystal structure and damages close arrangement of crystal grains. Moreover, higher boron content weakens dielectric properties of CBS glass-ceramics. In this study, the best molar ratio of ingredients, meeting the ideal target material, is n(Ca): n(Si): n(B) =?1:1:0.6. After optimal sintering procedure, dielectric constant of the best sample was 6 (1?MHz), 6 (10?MHz), and dielectric loss was 2.27?×?10^?3 (1?MHz) and 3.37?×?10^?3 (10?MHz). We demonstrate that the optimal boron content and sintering procedure is required to attain desired dielectric properties of CBS glass-ceramics.     

Columbite-rich multiphase TiO2 nanoceramic with superior mechanical and dielectric properties

Columbite-rich multiphase TiO₂ nanoceramics with outstanding mechanical and dielectric properties were successfully prepared through high-pressure sintering by using anatase-type TiO₂ as precursor. High-pressure sintering combined with phase transformation assisted consolidation can effectively refine the grain size of the recovered samples. This process is conducive to obtain nanocrystalline columbite-rich TiO₂ ceramics with excellent performance. The highest hardness is approximately 12.76 GPa, which is 2.5 times higher than that of ordinary coarse-grained ceramics. The effect of columbite phase on the hardness of multiphase ceramics is discussed. The columbite-rich TiO₂ ceramic shows a colossal permittivity (～8 × 10³) and low loss (～0.2) at 1 kHz and room temperature, which are superior to that of undoped rutile polycrystalline ceramics. This ceramic shows a steadier frequency-dependent dielectric permittivity and loss than rutile TiO₂ crystal. These results enrich the fundamental knowledge of columbite-rich TiO₂, thereby enabling the exploitation of new applications.     

Preparation of porous Y2SiO5 ceramics with high porosity and extremely low thermal conductivity for radome applications

It is well known that aqueous gel-casting is challenging to prepare high-porosity ceramics due to the considerable drying shrinkage, cracking, and deformation of green bodies during drying caused by the high surface tension of water. Porous Y₂SiO₅ ceramics with high porosity were prepared by introducing carbon fibers as a support material in the drying process of aqueous gel-casting to reduce shrinkage during drying. Burning out the carbon fibers after drying does not negatively affect the properties of the porous ceramic. As prepared green bodies by aqueous gel-casting have low shrinkages of 8.69%–6.81% during drying processes and high compressive strength of 13.73 ± 1.55–10.66～0.49 MPa. The higher compressive strength of the green body has a positive significance for processing porous ceramics into special-shaped structures. As prepared porous Y₂SiO₅ ceramics have high porosity of 73.94%–87.71%, lightweights of 1.16–0.55 g?cm³, extremely low thermal conductivities of 0.134 ± 0.006 to 0.051 ± 0.001 W?m^?1?k^?1, relatively low dielectric constants of 2.34–1.58, and tan δ are lower than 1.25 × 10^?3. Porous Y₂SiO₅ ceramics with excellent dielectric properties and thermal insulation properties meet the requirements of thermal insulation and wave transmission integration of radome materials. Aqueous gel-casting also enriches the preparation methods of high-porosity Y₂SiO₅ ceramics.     

Higher permittivity of Ni-doped lead zirconate titanate,Pb[(Zr0.52Ti0.48)(1-x) Nix]O3, ceramics

The paper reports highest obtained dielectric constant for Ni-doped Lead Zirconate Titanate [PZT, Pb(Zr_0.52Ti_0.48)O₃] ceramics. The Ni-doped PZT ceramic pellets were prepared via conventional solid-state reaction method with Ni content chosen in the range 0–20?at%. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were employed to investigate the crystal structure of the prepared ceramics. The X-ray diffraction analysis indicated that the ceramic pellets had crystallized into tetragonal perovskite structure. A minute displacement of XRD peaks was detected in the diffraction spectra of Ni-doped PZT ceramic samples which when examined by size-strain plot (SSP) method revealed presence of homogenous strain that decreased with increase in concentration of Ni. In FTIR the maximum absorption at 597?cm^?1, 608?cm^?1, 611?cm^?1, 605 and 613?cm^?1 for Ni?=?0, 5, 10, 15 and 20?at%, respectively, confirmed the formation of perovskite structure in all the compositions and the slight shift suggests decrease in cell size on doping. The values of dielectric constant (ε′) & tanδ as a function of frequency and temperature were measured for the prepared ceramics and it revealed highest ever reported dielectric constant for Ni - doped PZT with Ni?=?5?at%. The dielectric variation with temperature exhibited a diffused type ferroelectric–paraelectric phase transition for the doped samples. Also, the maximum dielectric constant value (ε′_max) decreased while the phase transition temperature increased with increase in doping concentration of Ni. The estimated activation energy of different compositions was found to increase from 0.057 to 0.068?eV for x?=?0.00 to x?=?0.20 in ferroelectric phase. The piezoelectric, ferroelectric and magnetic properties were also investigated.     

Simultaneously with large energy density and high efficiency achieved in NaNbO3-based relaxor ferroelectric ceramics

Dielectric capacitors are in urgent need of miniaturized and lightweight products. The new lead-free NaNbO₃-based ferroelectric ceramic material is a good choice owing to its high energy storage density, superior charge/discharge performance and decent frequency/temperature stability. In this work, a novel lead-free relaxor ferroelectric ceramic, (1-x)NaNbO₃-xBa(Mg_1/3Nb_2/3)O₃ [(1-x)NN-xBMN, x = 0.18, 0.20, 0.22 and 0.24], was designed and prepared via a local random field strategy. The impedance analysis demonstrates that the introduction of BMN could enhance the insulation ability and breakdown strength of the (1-x)NN-xBMN ceramic. Finally, the excellent energy storage performances with simultaneously ultrahigh energy storage density (W_st～4.04 J/cm³), recoverable energy storage density (W_rec～3.51 J/cm³), efficiency (η～87 %) and fatigue endurance (number of cycles: 5000) are obtained in the 0.78NN-0.22BMN ceramic. In addition, excellent frequency (1～100 Hz) and temperature stability (20～140 °C) can also be observed in the 0.78NN-0.22BMN ceramic. It is crucial that the ceramic shows extremely short charge-discharge time (t_0.9～45 ns), tremendous current density (C_D～680 A/cm²), giant power density (P_D～47.6 MW/cm³) and excellent temperature stability (30～150 °C). These results indicate that 0.78NN-0.22BMN ceramic is a promising dielectric capacitor material.     

Colossal dielectric properties of Na1/3Ca1/3Sm1/3Cu3Ti4O12 ceramics: Computational and experimental investigations

A modified sol?gel technique was used to synthesize a high dielectric ceramic, Na_1/3Ca_1/3Sm_1/3Cu₃Ti₄O₁₂. The crystal structure of this sintered ceramic matches the standard pattern of a body?centered cubic (bcc) system within the Im3 space group (JCPDS No. 75–2188). No impurity phases were observed. Interestingly, a high dielectric permittivity of ～1.14–1.35 × 10⁴ and a low loss tangent of ～0.027–0.039 were achieved in this sintered Na_1/3Ca_1/3Sm_1/3Cu₃Ti₄O₁₂ ceramic. Our DFT calculations disclosed that substitution of Na⁺ ions at Cu²⁺ sites causes an observed excess Cu concentration. As a result, metastable insulating phases were formed at a relatively high sintering temperature. Additionally, our electron density calculations revealed that Na ions lose their electrons to Sm ions, whereas the oxidation states of Cu and Ti are unaltered. Our results show that Cu⁺ and Ti³⁺ were observed after introducing an oxygen vacancy into this lattice. Significantly different values of R_g, R_gb, and E_g, E_gb support an internal barrier layer capacitor as the most likely origin of the giant dielectric properties of this ceramic. XPS results show mixed Cu⁺/Cu²⁺ and Ti³⁺/Ti⁴⁺ in all ceramics, suggesting that electron hopping between Cu⁺?Cu²⁺ and Ti³⁺?Ti⁴⁺ is the probable origin of the n?type semiconducting state inside the grains.     

Pb-free (Ba1−xCax) (Zr0·18Ti0.82)O3 dielectric tunable ceramics with giant figure-of-merit under low electric field

Dielectric tunable devices with improved overall tunability properties are in urgent demand for tunable applications. Hence, a series of Pb-free dielectric tunable ceramics based on (Ba_1?xCa_x) (Zr_0·18Ti_0.82)O₃ (abbreviated as BCZTx, x = 0.05–0.21, corresponding to BCZT05 to BCZT21) were carefully prepared using the traditional solid-state route in this work. The crystal structure, surface morphology, dielectric properties, and tunable performance of different BCZTx ceramics at room temperature (RT) were systematically studied. The temperature-dependent dielectric tunable performance was further investigated. The phase evolutions were co-confirmed by XRD and $\frac{d{\epsilon }_r}{dT}$-T curves. Interesting, high tunability (86.09%), together with a relatively low dielectric loss (~0.19% @7.42 kV/cm) were obtained in BCZT09 ceramics at 1 kHz, resulting in a giant figure-of-merit (FOM) of 448, which implied these ceramics are promising matrix for dielectric tunable applications that operated at RT. From the Tunability?T and FOM?T curves, it can be found that Ca²⁺ incorporation can improve the temperature stability of dielectric tunable performance to a certain extent. In addition, the FOM?T curve of BCZT09 showed advantages over other compositions in the temperature range of ?20 °C–85 °C, and its maximum FOM (~886) was reached at 40 °C. These observations suggest the BCZT09 ceramic as a promising matrix for application in dielectric tunable devices operating at RT. This work may guide the design of novel high-performance tunable ceramic materials.     

Improved non-ohmic and dielectric properties of Cr3+ doped CaCu3Ti4O12 ceramics prepared by a polymer pyrolysis solution route

CaCu_3-xCr_xTi₄O₁₂ (x?=?0.00–0.20) ceramics were prepared via a polymer pyrolysis solution route. Their dielectric properties were improved by Cr³⁺ doping resulting in an optimal dielectric constant value of 7156 and a low tanδ?value of 0.092 in a sample with x?=?0.08. This might have resulted from a decrease in oxygen vacancies at grain boundaries. XANES spectra confirmed the presence of Cu⁺ ions in all ceramic samples with a decreasing Cu⁺/Cu²⁺ ratio due to an increased content of Cr³⁺ ions. All CaCu_3-xCr_xTi₄O₁₂ ceramics showed nonlinear characteristic with improvement in both the breakdown field (E_b) and its nonlinear coefficient (α). Interestingly, the highest values of α, ～ 114.4, and that of E_b, ～8455.0?±?123.6?V?cm^?1, were obtained in a CaCu_3-xCr_xTi₄O₁₂ sample with x?=?0.08. The improvement of dielectric and nonlinear properties suggests that they originate from a reduction of oxygen vacancies at grain boundaries.     

Preparation of an environment-friendly LTCC material by using waste soda-lime glass and natural volcanic ash

Glass/ceramic composites applied in the field of low-temperature co-fired ceramics (LTCC) were successfully prepared at 670–710 °C by using waste soda-lime glass (WG) as a binder and natural volcanic ash as a ceramic raw material. Based on the theories of suppression and supplementary network effects, alkaline-earth metal ions (R²⁺, R = Mg, Ca, Sr, and Ba) and B₂O₃ were applied to improve the dielectric properties of WG and composites, respectively. The influence of R²⁺ on the crystal phase evolution, microstructure, mechanical, dielectric, and thermal properties of WG-volcanic ash-based composites were systematically investigated. By doping 2.5 wt% Ba²⁺ to the environment-friendly LTCC composites, physical properties i.e., ε_r of 4.86 at 1 MHz, tan δ of 6.32 × 10^?3, coefficient of thermal expansion of 8.72 × 10^?6/°C, and thermal conductivity of 1.04 W/(m·K) are obtained. It is worth mentioning that the environment-friendly LTCC composite uses WG with a low glass transition temperature to reduce the sintering temperature and a tiny amount of a modifier to adjust the dielectric performance instead of synthesizing specific crystals by adding lots of chemical reagents. These, in turn, do not only have the potential to be used in the LTCC packaging technology but also have significance for sustainable development. Additionally, because of good chemical compatibility between aluminum and the composites, the environment-friendly LTCC composites with ultra-low sintering temperature have the potential ability to lower the cost of LTCC packaging materials.     

Structure,electrical and dielectric properties of Ca substituted BaTiO3 ceramics

BaTi_1-xCa_xO_3-x [BTC100x] ceramics were synthesized via solid-state reaction method. Effect of Ca substitution on the structure, electrical and dielectric properties of BTC100x ceramics was systematically investigated. Calcined BTC100x powders were in tetragonal phase when x?≤?0.01, whereas transformed to cubic at x?>?0.01. Additionally, the diffraction peak (200) shifted to lower angles with increasing x, indicating increased unit cell volume. Meanwhile, Ba_0.97Ca_0.03TiO₃ [BC3T] ceramic was prepared and studied, to compare with BaTi_0.97Ca_0.03O_2.97 (BTC3). It was found that pure BaTiO₃ [BT] and BC3T ceramics had the similar structural and dielectric properties, whereas BTC3 ceramic showed much difference，XRD patterns, Raman spectrum, impedance spectra and dielectric-temperature spectra provided strong evidence of Ca²⁺ substitution at Ti site in BT lattice. Finally, BTC100x ceramics were produced and dielectric properties were investigated. With increasing x, the Curie temperature decreased from 128?°C (BT) to 42?°C (BTC5).     

Enhanced relative permittivity in niobium and europium co-doped TiO2 ceramics

The appearance of colossal permittivity materials broadened the choice of materials for energy-storage applications. In this work, colossal permittivity in ceramics of TiO₂ co-doped with niobium and europium ions ((Eu_0.5Nb_0.5)_xTi_1-xO₂ ceramics) was reported. A large permittivity (ε_r ～ 2.01?×?10⁵) and a low dielectric loss (tanδ ～ 0.095) were observed for (Eu_0.5Nb_0.5)_xTi_1-xO₂ (x?=?1%) ceramics at 1?kHz. Moreover, two significant relaxations were observed in the temperature dependence of dielectric properties for (Eu, Nb) co-doped TiO₂ ceramics, which originated from defect dipoles and electron hopping, respectively. The low dielectric loss and high relative permittivity were ascribed to the electron-pinned defect-dipoles and electrons hopping. The (Eu_0.5Nb_0.5)_xTi_1-xO₂ ceramic with great colossal permittivity is one of the most promising candidates for high-energy density storage applications.     

Dielectric properties of CaCu3Ti4O12 ceramics with Zn substitution for Cu

Abstract

CaCu_3–xZn_xTi₄O₁₂ (x is from 0 to 1·0) polycrystalline samples were fabricated via a two-step solid state reaction process. The lattice parameter of the monophasic CaCu₃Ti₄O₁₂ phase increased as Zn content increased. Scanning electron microscopy (SEM) images of the CCTO ceramic show bimodal grain size distribution and the grain size decrease largely with the appearance of Zn₂TiO₄ second phase. The dielectric permittivity of pure CCTO ceramic is ～1·5×10⁴ at f?=?100 Hz. The dielectric constant of the sample largely increased with Zn substitution in the frequency range f<10⁴ Hz. The highest dielectric constant was 6·2×10⁴ at f?=?100 Hz with Zn substitution of x?=?0·8. The improved dielectric properties are believed to be related to the presence of a thin grain boundary barrier layer. The resistivity of the grain boundary decreased largely with Zn substitution as evidenced from the impedance plots.     

Control of coring effect in BaTi4O9 microwave dielectric ceramics by doping with Mn4+

In the present work, we have attempted to reduce the effect of coring effect in the titanate ceramic system BaTi₄O₉ (BT4) by doping it with Mn⁴⁺. The microwave dielectric BaTi₄O₉ ceramics doped with 0, 0.5 and 1.0 mol% Mn⁴⁺ were synthesized by conventional ceramic processing route. The XRD studies confirmed a single phase crystalline structure for all the ceramic samples studied. The SEM micrographs of the ceramics reveal a microstructural change leading towards a more uniform grain size distribution as the Mn⁴⁺ content increases to 1.0 mol%. In the low frequency region (100 Hz to 1 MHz), the temperature stability of dielectric properties exhibits a marked improvement with the increasing amount of Mn⁴⁺ in the ceramic system. In the microwave frequency region (9.3 GHz), Q-factor increases from 11,625 GHz to 46,500 GHz for BaTi₄O₉ ceramic doped with 1.0 mol% Mn⁴⁺. The present paper reveals that the commonly observed degradation of dielectric properties due to coring effect in the BaTi₄O₉ ceramic system can be controlled by doping it with an appropriate quantity of Mn⁴⁺.     

Effect of pore size and porosity on piezoelectric and acoustic properties of Pb(Zr0.53Ti0.47)O3 ceramics

We studied the effect of porosity and pore morphology on the functional properties of Pb(Zr_0.53Ti_0.47)O₃ (PZT) ceramics for application in high frequency ultrasound transducers. By sintering a powder mixture of PZT and polymethylmetacrylate spherical particles (1.5 and 10?μm) at 1080°C, we prepared ceramics with ～30% porosity with interconnected micrometer sized pores and with predominantly ～8?μm spherical pores. The acoustic impedance was ～15?MRa for both samples, which was lower than for the dense PZT. The attenuation coefficient α (at 2.25?MHz) was higher for ceramics with ～8?μm pores (0.96?dB?mm^??1?MHz^??1), in comparison to the ceramic with smaller pores (0.56?dB?mm^??1?MHz^??1). The high α value enables the miniaturisation of the transducer, which is crucial for medical imaging probes. The dielectric and piezoelectric coefficients, polarisation, and strain response decreased with increased porosity and decreased pore/grain size. We suggest a possible role of pore/grain size on the switching behaviour.     

Dielectric and microwave absorption properties of divalent-doped Na3Zr2Si2PO12 ceramics

The work attempted to develop a new kind of high temperature microwave absorption material. Dense Na₃Zr_1.9M_0.1Si₂PO_11.9 (M?=?Ca²⁺, Ni²⁺, Mg²⁺, Co²⁺, Zn²⁺) and Na₃Zr_2-xZn_xSi₂PO_12-x (x?=?0.1, 0.2, 0.3, 0.4) ceramics were prepared by solid-state reactions for phase, microstructure characterization and dielectric properties, microwave absorption properties analysis. Results show that the complex permittivity increases in all the divalent-doped Na₃Zr₂Si₂PO₁₂ ceramics. Na₃Zr_1.8Zn_0.2Si₂PO_11.8 ceramic exhibits the highest complex permittivity and optimum microwave absorption performance. The lowest reflection loss is -28.1?dB at 9.88?GHz and the bandwidth is 4.14?GHz (8.26–12.4?GHz) with a thickness of 2.1?mm. It indicates that Na₃Zr₂Si₂PO₁₂ ceramic can be chosen as a potential candidate of microwave absorption material and the performance can be enhanced by divalent doping strategy.     

Effect of yttrium (Y) substitution on the structure and dielectric properties of BaTiO3

As the rate of application of multilayer ceramic capacitors (MLCCs) in small electronic devices increases, the use of the raw material barium titanate (BaTiO₃) with a small particle size and excellent dielectric properties becomes needed. Due to the size effect, small-sized BaTiO₃ generally has a cubic phase structure with a low dielectric constant, which limits its use in MLCCs. We report the preparation of small cubic phase Y-doped BaTiO₃ (BYT) nanoparticles by a hydrothermal method and the preparation of highly dielectric tetragonal phase BYT ceramics based on this method. XRD and Raman analysis showed that the BYT nanoparticles are in substable cubic phases. The particle size of the BYT nanoparticles, measured by TEM, XRD, and BET, was approximately 35 nm. The dielectric properties of the BYT ceramics were tested by an impedance analyzer, and the dielectric constant of the BYT ceramics was 7547 when the Y³⁺ doping amount was 0.5 mol%. In addition, the substitution mechanism of Y³⁺ doping in BaTiO₃ crystals was proposed from XPS and EPR analysis. The results demonstrate for the first time that the 50 nm cubic phase BaTiO₃ powder can meet the needs of next-generation high-capacity MLCCs. This work provides a reference for small cubic phase BaTiO₃ as a dielectric material for high-capacity MLCCs.     

Ultra-stable X9R type CaCu3-xZnxTi4.1O12 ceramics

CaCu_3-xZn_xTi_4.1O₁₂ (x?=?0.00, 0.05 and 0.10) precursor powders were prepared by the polymer pyrolysis (PP) solution method. Ultra-stable X9R type capacitor with very low loss tangent (tanδ) ~0.017 varied within a value of less than 0.05 in a wide temperature range of ?60 to 150?°C and high dielectric constants (ε^′) ~9200 with Δε′ ≤?±?15% in a wide temperature range of ?60 to 210?°C was achieved in CaCu_2.95Zn_0.05Ti_4.1O₁₂ (Zn05-1) ceramic obtained by sintering the precursor powder (x?=?0.05) at 1060?°C for 8?h. A major role for the validity of ε^′ and tanδ in these wider temperature ranges was suggested to originated from the very high grain boundary resistance (R_gb ~413,190?Ω?cm), resulting from the effect of Zn²⁺ doping and TiO₂-rich at grain boundary. With the excellent dielectric properties of (Zn05-1) ceramic, it was suggested to be applied for X8R and X9R capacitors. Interestingly, improvements of nonlinear properties with very high nonlinear coefficient (α ~ 25.94) and breakdown field (E_b~ 3146.25?V.cm^?1) values were achieved in (Zn05-1) ceramic, as well.     

Magneto-dielectric laminated Ba(Fe0.5Nb0.5)O3-Bi0.2Y2.8Fe5O12 composites with high dielectric constant and high permeability

Magneto-dielectric laminated ceramic composites of xBa(Fe_0.5Nb_0.5)O₃-(1-x)Bi_0.2Y_2.8Fe₅O₁₂(BFN-BYIG) with high volume fractions of the giant dielectric constant material BFN (x=10, 30, 50, 70 wt%) were fabricated by the solid-state sintering method. Microstructure, dielectric and magnetic properties of the composites were investigated. The composites possess stable dielectric properties in the frequency range from 100 Hz to 1 MHz with high dielectric constant and low dielectric loss. The maximum permeability of the magneto-dielectric laminated composites reaches up to about 25. And the magnetic behaviors are strongly dependent on the mass ratio of BYIG. The results indicate that such multilayer structures of BFN/BYIG can enhance the permeability and decrease the dielectric and magnetic loss efficiently.