Dielectric Properties of Ag（Nb1-xTax）O3 and Bi2O3 Doped Ag（Nb1-xTax）O3 Ceramics

Dielectric properties of Ag（Nb1-xTa）O3 and Bi2O3 doped Ag（Nb1-xTax）O3 solid solutions were investigated. The results show that with the increase of Ta content （x）, the sintering temperature increased, and the dielectric loss （tanδ） and the temperature coefficient （αc） decreased. Ag（Nb1-xa）O3 （x=0.4） ceramics sintered at 1 100℃ had the highest permittivity （516.8） and a lower tanδ （0.0021） at 1 MHz, and its temperature coefficient was about 191 ppm/℃. The sintering temperature of Ag（Nb1-xTa）O3 （x=0.4） was lowered by the addition of Bi2O3, and its dielectric properties were improved. Ag（Nb0.6Ta0.4）O3 ceramics with 2.5 wt% Bi203 addition presented the optimum dielectric properties （ε=566, tanδ= 0.0007 and αc≈0ppm/℃） （1 MHz）,     

The microstructure and properties of Ag(Nb0.8Ta0.2)1−x (Mn0.5W0.5) x O3 ceramic system

The microstructure and dielectric properties of Ag(Nb0.8Ta0.2)1-x(Mn0.5W0.5)xO3(x=0,0.04,0.08,0.12,0.16) ceramic system were investigated.The Ag(Nb0.8Ta0.2)1-x(Mn0.5W0.5)xO3 ceramics were prepared by the traditional solid-state reaction method and were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM) and Raman spectrometer.The sintering ability and dielectric properties of Ag(Nb0.8Ta0.2)1-x(Mn0.5W0.5)xO3 were found to be improved with the doping of Mn4+ and W6+ ions.The densification temperature of Ag(Nb0.8Ta0.2)1-x(Mn0.5W0.5)xO3 ceramics decreased from 1 080 ℃ to 1 000 ℃ when x increased from 0 to 0.16.Ag(Nb0.8Ta0.2)1-x(Mn0.5W0.5)xO3 ceramic was found to have the best dielectric properties when x=0.08,larger permittivity(■=547) and smaller dielectric loss(tan■=0.00156).     

La2O3、Cr2O3共掺杂的CCTO陶瓷介电性能研究

采用氧化物混合工艺制备了La2O3和Cr2O3共掺杂的CaCu3Ti4O12(CCTO)陶瓷材料。通过XRD、介电温度特性等测试手段,研究了掺杂不同浓度的La2O3和Cr2O3对CCTO体系陶瓷介电性能的影响,并对掺杂机理进行了分析.研究结果表明:分别掺杂La2O3和Cr2O3的CCTO陶瓷的介电损耗为～0.2,比纯的CCTO陶瓷样品低,而介电常数仍保持在～104;掺杂0.03at%La2O3和0.08at%Cr2O3的CCTO陶瓷材料的介电常数为4.4×104,介电损耗可降至0.15.因此,通过共掺杂的方法可以在有效降低CCTO陶瓷介质损耗的同时,仍维持高的介电常数.     

Structure and dielectric properties of ZnO and Nb<Subscript>2</Subscript>O<Subscript>5</Subscript> doped BaO-TiO<Subscript>2</Subscript> system microwave ceramics

The microwave dielectric properties and microstructure of BaTi4.3ZnyO9.6＋y ＋0.02 mol% SnO2＋0.01 mol% MnCO3＋x mol% Nb2O5（x=0-0.05, y=0-0.08） system ceramics were studied as a function of the amount of ZnO and Nb2O5 doped. Addition of （y=0-0.05） ZnO and （x=0-0.025） Nb2O5 enhanced the reactivity and decreased the sintering temperature effectively. It also increased the dielectric constant ε r and quality factor Q（=1/tan 8） of the system due to the substitution of Ti^4＋ ions with incorporating Zn^2＋and Nb^5＋ ions, which was analyzed by the reaction ZnO＋Nb2O5＋ 3 TiTxTi →ZnTi＋ 2NbTi＋3TiO2. When the system doped with （y=0.05） ZnO and （x=0.025） Nb205 were sintered at 1 160 ℃ for 6 h, the εr. Qf0 value and rfwere 36.5, 42 000 GHz, and＋1.8 ppm/℃, respectively, at 5 GHz.     

Low-temperature sintering and microwave dielectric properties of Ba<Subscript>2</Subscript>Ti<Subscript>3</Subscript>Nb<Subscript>4</Subscript>O<Subscript>18</Subscript> ceramics

The effects of CuO and H3BO3 additions on the low-temperature sintering,microstructure,and microwave dielectric properties of Ba2Ti3Nb4O18 ceramics were investigated.The addition of less amount of CuO (< 1 wt%) considerably facilitated the densification of Ba2Ti3Nb4O18 ceramics.Appropriate addition of H3BO3 (< 3.5 wt%) remarkably improved the microwave dielectric properties of ceramics.The addition of H3BO3 and CuO successfully reduced the sintering temperature of Ba2Ti3Nb4O18 ceramics from 1300 to 1050 ℃.B...     

Preparation, Characterization and Dielectric Properties of Ba6Mg0.67Nb9.33O30 Ceramic

A new niobate Ba6Mg0.67Nb9.33O30 was ssnthesized in the BaO-MgO-Nb2O5 system by solid state reaction at 1350 ℃ for 48 b. The strncture and dielectric properties of Ba6Mg0.67Nb9.33O30 were determined by X-ray pouder diffraction, straining electron microscopy and dielectric measurements. The results show that Ba6Mg0.67Nb9.33O30 belongs to ferroelectric phase of filled tetragonal tungsten bronze structure at room temperature with unit cell parameters ： a = 1. 26052（4） nm , c = 0.40045（2） nm, space group P4bm , calculated density 5 . 707g. cm ^-3 . Ba6Mg0.67Nb9.33O30 belongs to relaxor ,ferroetectrics undergoing diffusive phase transition, and the transition temperature （ Tc ） is 30 ℃ observed at 10 kHz. At room temperature, Ba6Mg0.67Nb9.33O30 eeramic has a high dielectric constant 850 at 1 MHz and a low dielectric loss of 0. 0052.     

Effect of sintering aid CuO-MnO2 on dielectric properties of 0.5Ba(Mg1/3Nb2/3)O3-0.5Ba(Ni1/3Nb2/3)O3 ceramics

Microstructures and microwave dielectric properties of 0.5Ba(Mg_1/3Nb_2/3)O₃-0.5Ba(Ni_1/3Nb_2/3)O₃ ceramics with x wt% CuO−x wt% MnO₂ additions (x=0.25–1) prepared by conventional solid-state route were investigated. It is found that low level-doping of CuO-MnO₂ can significantly improve the density of the specimens and their microwave dielectric properties. The relative density of 0.5Ba(Mg_1/3Nb_2/3)O₃-0.5Ba(Ni_1/3Nb_2/3)O₃ ceramics can be increased by 95% sintering at 1 330 °C due to the liquid phase effect. The second phase is not observed in ceramics with CuO-MnO₂ addition. The parameter ε _r increases with increasing sintering temperature, and Q _f is effectively promoted by CuO-MnO₂ addition. Higher CuO-MnO₂ content would make τ_f value more positive. Meanwhile, ε _r value of 30.5, Q _f value of 63 200 GHz and τ _f value of 0.5 ppm/°C were obtained for 0.5Ba(Mg_1/3Nb_2/3)O₃-0.5Ba(Ni_1/3Nb_2/3)O₃ ceramics with 0.5 wt% CuO-0.5 wt% MnO₂ addition sintered at 1 330 °C for 4 h.     

Structural and Dielectric Properties of Ba5RNiNb9O30 （R = La, Nd and Sm） ceramics

1 IntroductionSince the discovery of ferroelectricity and relatedproperties in BaTiO3,a large amount of research work onoxidesin search of novel materials for industrial applica-tions ,has been done .High performance dielectric ceram-ics are applied as key materials for resonators , discreteand multiplayer (MLC) capacitors ,andtemperature com-pensating capacitors . Some ferroelectric oxides are alsovery important due to the rapid progress in microwavetelecommunications ,satellite broadcastin…     

Microstructures and characteristics of deep trap levels in ZnO varistors doped with Y2O3

In this paper discussions on ZnO based varistor ceramics doped with different ratios of Y₂O₃ are presented. Analysis on the phase and microstructures of the samples indicates that an additional phase is detected in the samples doped with Y₂O₃, and the average grain size of the specimens decreases from about 9.2 μm to 4.5 μm, with an increase in the addition of Y₂O₃ from 0 mol% to 3 mol%. The corresponding varistor’s voltage gradient markedly increases from 462 V/mm to 2340 V/mm, while the nonlinear coefficient decreases from 22.3 to 11.5, respectively. Furthermore, the characteristics of deep trap levels in these ZnO samples are investigated by measuring their dielectric spectroscopies. The trap energy level and capture cross section evaluated by relaxation peak of the Cole-Cole plot vary slightly as the addition of Y₂O₃ increases. These traps may be ascribed to the intrinsic defects of ZnO lattice.     

Dielectric properties of Pb (Zn1/3 Nb2/3) O3?PbZrO3?PbTiO3 solid solution near morphotropic phase boundary

The dielectric properties of Pb(Zn_1/3Nb_2/3) O₃-PbZrO₃−PbTiO₃ (PZN-PZ-PT) system near the rhombohedral/tetragonal morphotropic phase boundary (MPB) are carefully studied in this paper. It is found that, for all samples, the curves around the temperatures of dielectric permittivity peak show the characteristics of diffuse phase transition. The change in PbZrO₃/PbTiO₃ ratio has much influence on the dielectric properties of the samples. The extent of diffuse phase transition increases with the increasing Zr/Ti ratio. The samples in rhombohedral region have typical diffuse phase transition in the temperature range measured. However, for the samples with tetragonal symmetry, a spontaneous normal ferroelectric-relaxor phase transition exists at temperature lower than that of permittivity peak. This normal ferroelectric-relaxor phase transition is confirmed by the experiment of thermally driven current. The analysis of TEM reveals that the samples in tetragonal region show a 90% macrodomain structure, while the samples in rhombohedral region have the configuration of microdomain structure.     

Preparation and piezoelectric properties of CuO-added (Ag<Subscript>0.75</Subscript>Li<Subscript>0.1</Subscript>Na<Subscript>0.1</Subscript>K<Subscript>0.05</Subscript>)NbO<Subscript>3</Subscript> lead-free ceramics

CuO-doped (Ag_0.75Li_0.1Na_0.1K_0.05)NbO₃ (ALNKN-xCuO, x = 0–2mol%) lead-free piezoelectric ceramics were prepared by the solid-state reaction method in air atmosphere. The effects of CuO addition on the phase structure, microstructure, and piezoelectric properties of the ceramics were investigated. The experimental results show that the ALNKN ceramics without doping CuO possess rhombohedral phase along with K2Nb6O16-type phase and metallic silver phase. For all of the CuO-doped ALNKN ceramics, a pure perovskite structure with the orthorhombic phase was obtained by enclosing the samples in a corundum tube. A homogeneous microstructure with the grain size of about 1 μm was formed for the ceramics with 0.5mol% CuO. The grain size increases with increasing amount of CuO. The temperature dependence of dielectric properties indicates that the ferroelectric phase of the ALNKN-xCuO ceramics becomes less stable with the addition of CuO. The ceramics with x = 1mol% exhibit relatively good electrical properties along with a high Curie temperature. These results will provide a helpful guidance to preparing other AN-based ceramics by solid-state reaction method in air atmosphere.     

Low-temperature sintering and microwave dielectric properties of Li2MgTi3O8 ceramics doped with BaCu（B2O5）

The influences of BaCu(B₂O₅) (BCB) addition on sintering, microstructure and microwave dielectric properties of Li₂MgTi₃O₈ ceramics were investigated using X-ray diffractometry, scanning electron microscopy and microwave dielectric measurements. The experimental results show that a small amount of BaCu(B₂O₅) addition can effectively reduce the sintering temperature to 900 °C, and induce only a limited degradation of the microwave dielectric properties. Typically, the best microwave dielectric properties of ɛ _r=24.5, Q×f =24 622 GHz, τ _f=4.2×10⁻⁶ °C⁻¹ are obtained for 1.0% BCB-doped Li₂MgTi₃O₈ ceramics sintered at 900 °C for 3 h. The BCB-doped Li₂MgTi₃O₈ ceramics can be compatible with Ag electrode, which may be a strong candidate for low temperature co-fired ceramics applications.     

The influence of cobalt acetate on sol-gel derived mullite densification behaviour

Monophasic mullite (3Al2O3?2SiO2) samples doped with 0.002 M, 0.02 M, 0.1 M, 0.15 M and 0.2 M of cobalt were prepared by a sol-gel process. Prepared gels were then dried, grinded, pressed into pellets and sintered at 1 000 °C and 1 300 °C for 4 h. Phase formation and densification behavior has been investigated as a function of the cobalt content and sintering temperature. Mullite densification behavior was analyzed .The density of the sintered ceramics was measured using Archimedes method. CoO and Co related compounds were detected by the analysis for G3, G4 and G5 doping levels. The mullite X-ray diffraction suggests predominant incorporation of Co in the glassy phase, whose quantity increased with the doping level.     

助烧剂对(Zr_(0.8)S_(0.2))TiO_4晶相与介电性能的影响

采用传统的固相反应法制备(Zr0.8S0.2)TiO4陶瓷样品,研究不同含量ZnO、Fe2O3、NiO对(Zr0.8S0.2)TiO4材料的晶相、显微结构与介电性能的影响。结果表明:上述添加剂可以降低(Zr0.8S0.2)TiO4陶瓷的烧结温度,当助烧剂ZnO、Fe2O3、NiO的质量分数分别为0.5%、0.5%、0.2%时,烧结温度为1 350℃时已烧结成瓷,没有气孔,致密性好,具有α-PbO2型结构(Zr0.8Sn0.2)TiO4相;随着烧结温度的升高,陶瓷样品出现过烧,介电常数εr由1 300℃的39.833 4下降到1 400℃的26.298 4,介质损耗tanδ在10-3数量级。     

Glass-forming ability and chemical stability of magneto-optical glass heavily doped with rare earth oxide

The glass-forming region of B₂O₃-Al₂O₃-SiO₂ (BAS) glass heavily doped with rare earth oxides was investigated by an effective method, and the chemical stability was investigated by powder method. Influences of rare earth oxides on the glass-forming ability and the chemical stability of the BAS glass were also discussed. The experimental results show that the BAS glass-forming region expands firstly with the increase of the Tb₂O₃ content up to 30mol% and then shrinks. The acid-resistant capacity of the BAS glass doped with rare earth oxides is the lowest, the water-resistant capacity is secondary, and the alkali-resistant capacity is the best. Besides, the glass chemical stability can be improved by doping appropriate amount of rare earth oxides. Moreover, the stronger the ionic polarization ability of the rare earth ions is, the better the chemical stability of the BAS glass will be.     

Effect of Rare Earth Oxides on the Microstructure and Microwave Dielectric Properties of CaO-MgO-Nb2Os-TiO2 System Ceramics

La2O3 and SrO-doped CaO-MgO-Nb2O3-TiO2 system ceramics were prepared by solid-state ceramic technique.The microstructure and microwave dielectric properties of CaO-MgO-Nb2O5-TiO2-La2O3 cermics can be adjusted by varying the amount of La^3＋ or Sr^2＋ ions respectively.The replacement of Ca^2＋ by La^3＋ at A-site of the ceramics increases the quality factor Q value（ at 7.6GHz）as well as the temperature coefficient of resonant frequency τf and decreases the dielectric constant εr and the substitution of Sr^2＋ at A-site in this ceramics system exhibits opposite characteristics.The microwave properties of La^3＋,Sr^2＋-doped CaO-MgO-Nb2O5-TiO2 system ceramics depend on the degree of octahedral distortion inside materials.     

Formation and dielectric properties of Mn-Doped BSTN composite ceramics

The influence of Mn doping on the formation and dielectric properties of 0.7BaO·0.3SrO·(1−y)TiO₂·yNb₂O₅ (BSTN) composite ceramics were investigated. The Mn was doped according to the formula 0.7BaO·0.3SrO·(0.7−z)TiO₂·0.3Nb₂O₅·zMnO₂ (BSTNM). The results show the two phases, perovskite phase BST and the tungsten bronze phase SBN, are coexistence in BSTNM as they are in BSTN composite ceramics. The Mn ions doped in BSTN substitute for Nb⁵⁺ ions in the tungsten bronze phase, and then, the Nb⁵⁺ ions substitute for Ti⁴⁺ ions in the perovskite phase. With the increasing of Mn dopant, the content of the perovskite phase increases while that of the tungsten bronze phase decreases, and the grain size of the perovskite phase decreases. As well as, the phase transition temperature of tungsten bronze phase increases with value z increasing from 0 to about 0.05.     

A novel technique for probing phase transitions in ferroelectric functional materials: Condensed matter spectroscopy

As relaxor ferroelectric functional materials, their crystal structures depend on temperature, component, electric filed, pressure, and so on, which are important for the applications of sensors, transducers, and actuators. For the case of PbTiO₃-based ferroelectrics Pb(Zn_1/3Nb_2/3)O₃-PbTiO₃, Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃, Pb(In_1/2Nb_1/2)O₃-Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ and some other crystals, they have been extensively investigated due to the excellent electromechanical and piezoelectric properties. Generally, ferroelectric crystal structure and corresponding phase diagram are detected by temperature-dependent high resolution X-ray diffraction, low frequency dielectric permittivity, and domain structures. In this review, we focus on the novel condensed matter spectroscopy (i.e., spectroscopic ellipsometry, transmittance, photoluminescence spectra as well as Raman spectra), which is nondestructive, noncontact, and sensitive optical techniques for probing symmetries, phase transitions and phase diagrams of ferroelectric crystals. Besides, it can supply some other physical and chemical information for ferroelectric and semiconductor functional materials such as optical band gap, electronic transitions, dielectric functions, optical conductivity, absorption, phonon modes, lattice dynamics as functions of temperature and PT composition.     

Microstructure and microwave dielectric properties of CaO-B2O3-SiO2 glass ceramics with various B2O3 contents

The effects of B2O3 addition on both the sintering behavior and microwave dielectric properties of CaO-B2O3-SiO2 (CBS) glass ceramics were investigated by Fourier transform infrared spectroscopy (FTIR),X-ray diffractometry (XRD) and scanning electron microscopy (SEM).The results show that the increasing amount of B2O3 causes the increase of the contents of [BO3],[BO4] and [SiO4],which deduces the increase of CaB2O4 and α-SiO2 and the decrease of CaSiO3 correspondingly.No new phase is observed throughout the...     

Effect of ZnO-B<Subscript>2</Subscript>O<Subscript>3</Subscript> glass addition on the microwave dielectric properties of BaO-Nd<Subscript>2</Subscript>O<Subscript>3</Subscript>-TiO<Subscript>2</Subscript>-Bi<Subscript>2</Subscript>O<Subscript>3</Subscript> system

The effect of ZnO-B₂O₃(ZB) glass addition on the sintering behavior, microstructures and microwave dielectric properties of BaO-Nd₂O₃-TiO₂-Bi₂O₃ (BNTB) system was investigated with the aid of X-ray diffraction, scanning electron microscopy and capacitance meter. It is found that the ZB glass addition, acting as a sintering aid, can effectively lower the sintering temperature of BNTB system to 850 °C. The dielectric constant of BNTB-ZB ceramics increases with the increase of soaking time and the value of dielectric loss decreased with increasing soak time. The optical dielectric properties at 1 GHz of ɛ=74, tan δ=4×10⁻⁴, and TCC=25 ppm/°c were obtained for the BNTB system doped with 25 wt% ZB glass sintered at 850 °C for 2 h, representing that the BNTB-ZB ceramics could be promising for multilayer low temperature co-fired ceramics applications.