The structure and properties of Ag(Nb0.8Ta0.2)O3 ceramic doped with MnNb2O6

The influences of doping of MnNb2O6 on the structure and dielectric properties of Ag(Nb0.8Ta0.2)O3 were illustrated. Ag(Nb0.8Ta0.2)O3 samples doped with different amount of preformed MnNb2O6 (1 mol%, 2 mol%, 3 mol%, 4 mol%, 6 mol%, 8 mol%) were prepared by traditional solid-state reaction method and characterized by XRD, SEM and EDS, and the dielectric properties of samples were compared. The experiment results indicated that when the doping amount of MnNb2O6 was greater than 3 mol%, second phase appeared because of the solid solution limit. The permittivity of the Ag(Nb0.8Ta0.2)O3 samples doped with MnNb2O6 firstly increased and then decreased with the sintering temperature, while the dielectric loss decreased first, and then increased slightly. 1 100 ℃ seems to be the most proper sintering temperature for most of the samples. When the amount of MnNb2O6 is about 3 mol%, the samples have the best dielectric properties, larger permittivity and smaller dielectric loss.     

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）,     

Synthesis and Piezoelectric Properties of Lead-free （ Bi0.5 Na0.5 ）1-x（BaaSrb）xTiO3 Ceramics

A new group of lead-free piezoelectric ceramics,（Bi0.5 Na0.5）1-x（BaaSrb）xTiO3（abbreviated as BNBST[100x-100a/100b],0〈x〈1,a＋b=1）,was synthesized.The ceramics were prepared by conventional ceramic sintering technique,and the ceramics with density of 95% of the theoretical one can be sintered without the atmosphere control during the sintering process.The results of the X-ray diffraction（XRD） data show that the ceramics possess a single perovskite phase.The measurements of dielectric and piezoelectric properties reveal that the ceramics provide relatively high piezoelectric charge constant d33 and high planar electromechanical coupling factor kp.For the BNBST6-95/5 ceramics,d33 is equal to 170pC/N,and kp is equal to 32.0%.The fabrication technique for these ceramics is conventional and stable.     

Composition dependence of phase structure and electrical properties of (1−y)Bi1−xNdxFeO3−yBiScO3 ceramics

In this work, we have studied a new lead-free ceramic of(1-y)Bi_(1-x)Nd_xFeO_(3-y)BiScO_3(0.05≤x≤0.15 and 0.05≤y≤0.15) prepared by a conventional solid-state method, and the influences of Nd and Sc content on their phase structure and electrical properties were investigated in detail. The ceramics with 0.05≤x≤0.10 and 0.05≤y≤0.15 belong to an R3 c phase, and the rhombohedral-like and orthorhombic multiphase coexistence is established in the composition range of 0.125≤x≤0.15 and y=0. The electrical properties of the ceramics can be enhanced by modifying x and y values. The highest piezoelectric coefficient(d33~51 p C/N) is obtained in the ceramics with x=0.075 and y=0.125, which is superior to that of a pure BiFeO_3 ceramic. In addition, a lowest dielectric loss(tan δ~0.095%, f=100 k Hz) is shown in the ceramics with x=0.15 and y=0 due to the involvement of low defect concentrations, and the improved thermal stability of piezoelectricity at 20–600oC is possessed in the ceramics. We believe that the ceramics can play a meaningful role in the high-temperature lead-free piezoelectric applications.     

Effect of Li content on the microstructure and properties of lead-free piezoelectric （K0.5Na0.5）1-xLixNbO3 ceramics prepared by SPS

Lead-free piezoelectric （K0.5sNa0.5）1-xLixNbO3 （x = 0at%-20at%） ceramics were synthesized by spark plasma sintering （SPS） at low temperature and the effects of LiNbO3 addition on its crystal structure and properties were also studied. When the Li content was less than 6at%, a single proveskite phase with the similar structure of （K0.5Na0.5）NbO3 was formed; and a secondary phase with K3Li2Nb5O15 structure was observed in the 6at% 〈 x 〈 20at% compositional range. Furthermore, LiNbO3 existed as the third phase when the Li content was higher than 8at%. The grain sizes increased from 200-500 nm to 5-8 μm when the K3Li2Nb5O15 and LiNbO3 like phases were formed. With increasing Li content, the relative density of the ceramics first decreased from 97% to 93% and then kept constant. The piezoelectric coefficient d33, dielectric constant, and planner electromechanical coupling factor exhibited a decreasing tendency with increasing Li content because of the decrease in density and the formation of the secondary phase such as K3Li2Nb5O15 and LiNbO3. The formation of dense microstructure with a single phase is necessary in improving the properties of the （K0.5Na0.5）1-xLixNbO3 ceramics.     

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...     

Effects of Sr2＋ substitution on the structural,dielectric, and piezoelectric properties of PZT-PMN ceramics

This study described the structural, dielectric, and piezoelectric behavior of Pb1-xSrx[（Zr0.52Ti0.48）0.95（Mn1/3Nb2/3）0.05]O3 ceramics （PSZT-PMN, x=0, 0.025, 0.050, and 0.075）, prepared by a semi-wet route. X-ray diffraction, dielectric, and piezoelectric investigations were carried out to analyze the crystal structure. The relative dielectric constant and dielectric loss were both calculated as the functions of temperature. The room-temperature dielectric constant reaches a maximum for a Sr2＋-modified PZT-PMN ceramic with an x value of 0.050, which corresponds to the morphotropic phase boundary （MPB）. Raman spectroscopy studies also confirm the existence of this MPB for x=0.050. The piezoelectric strain coefficients （d33） value shows a maximum response for this composition. In addition, the phase transition temperature decreases significantly when the Sr2＋concentration increases in the PZT-PMN ceramics.     

Microstructures and Electrical Properties of Bi_(0.5)-(Na_(1-x-y)K_xLi_y)_(0.5)TiO_3 Lead-free Piezoelectric Ceramics

The microstructures and electrical properties of Bi0.5(Na1-x-yKxLiy)0.5TiO3 lead-free piezoelectric ceramics were studied.These ceramics were prepared by conventional ceramic technique.XRD analysis reveals that the ceramics possess almost pure perovskite phase when y≤0.2.The SEM results show that,with more amounts of Li+,the crystalline grain growing speed is accelerated,and the sintering temperature can effectively be decreased.The measurements of piezoelectric properties indicate that the ceramics with relatively low amount of Li+ and high amount of K+ have comparatively large piezoelectricity.The dielectric measurements show that the ceramics have properties like relaxor ferroelectrics and diffuse phase transition(DPT) at Td and Tc,respectively.The results of ferroelectric measurements reveal the system has relatively higher remanent polarization Pr(27.6 μC/cm2) and lower coercive field Ec(37.5 kV/cm).     

Dielectric and Magnetic Properties of (1-x)CaTiO_3-xNi_(0.5)Zn_(0.5)Fe_2O_4 Composite Ceramics

(1-x)CaTiO_3-xNi_(0.5)Zn_(0.5)Fe_2O_4(0 x 1.0) composite ceramics were synthesized by a conventional solid state reaction method.The phase formation,microstructure,and dielectric and magnetic properties were investigated by X-ray diffraction,scanning electron microscopy,precision impedance analysis,and vibrating sample magnetometry,respectively.The results indicate that the composite ceramics are composed of both perovskite phase Ca TiO_3 and spinel phase Ni_(0.5)Zn_(0.5)Fe_2O_4.The maximal relative density for 0.5CaTiO_3-xNi_(0.5)Zn_(0.5)Fe_2O_4 composite ceramics reaches 97.8%,as it has been sintered at the temperature of 1260 ℃ for 3 h.Dielectric constant and loss tangent of(1-x)CaTiO_3-xNi_(0.5)Zn_(0.5)Fe_2O_4 composite ceramics show dispersion in the low frequency range.Their phase transition temperature of the dielectric constant shifts to lower temperatures with the increase of Ni_(0.5)Zn_(0.5)Fe_2O_4 content.This phenomenon is attributed to that the phase transition temperature of CaTiO_3 is higher than that of Ni_(0.5)Zn_(0.5)Fe_2O_4.The saturation magnetization of (1-x)CaTiO_3-xNi_(0.5)Zn_(0.5)Fe_2O_4 composite ceramics increases with the Ni_(0.5)Zn_(0.5)Fe_2O_4 ferrite content.     

Effects of Sintering Technology on PMZN Piezoceramics Properties

Pb (Mn1/3Sb2/3) x(Zn1/3Nb2/3)y (Zr0.535Ti0.465)1-x-yO3(PMZN) piezoelectric ceramics were fabricated .The effects of sintering temperature and heat-treatment time on properties were discussed, the opti-mum preparation technology parameters were obtained. In this case, the ceramics have the highest electromechanical coupling coefficients and mechanical quality factor and the least dielectric loss. It is revealed that the PMZN piezo-ceramics material can be utilized for high-power ultrasound transducers.     

Structure and Electrical Properties of （Na0.5Bi0.5）0.94Ba0.06TiO3 Ceramicwith0.5wt% of MnO

The structure and electrical properties of （Na0.5Bi0.5）0.94Ba0.06TiO3 ceramic doped with 0.5 wt% of MnO were investigated in comparison with those of （Na0.5Bi0.5）0.94Ba0.06TiO3 ceramic. It was ascertained that the MnO addition did not cause remarkable change in crystal structure and microstructure. The MnO addition mainly displayed a hard effect on the electrical properties, an increase of coercive field （E） and mechanical quality factor （Qm） together with a decrease of dielectric constant （εr） and piezoelectric constant （d33）. An enhancement of electromechanical coupling factor （kp） with the MnO addition was obtained too. An essential relation between the piezoelectric properties and ferroelectric nature of the ceramics was detected. It was found that the piezoelectric properties of the ceramics highly depended on the corporative contribution of remanent polarization （Pt） and coercive field.     

Effects of NaNbO_3-Co_2O_3 Co-additive on the Properties of PZN-PZT Ceramics

NaNbO_3-Co_2O_3 co-added PZN-PZT(PZCNNT)ceramics were prepared using conventional solid state reaction.The piezoelectric and dielectric properties were measured.The experimental results show that the addition of 0.3mol% Co_2O_3 leads to low dielectric loss(tgδ)in PZCNNT ceramics and the proper addition of NaNbO_3 not only improves piezoelectric properties but also decreases intensively dielectric loss and mechanical loss.The optimal ceramic having d_(33)=310 pC/N,k_p=0.59,ε_r=985,tgδ=0.0034,Q_m=1380 was obtained.     

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 f...     

Effect of milling process on the core-shell structures and dielectric properties of fine-grained BaTiO3-based X7R ceramic materials

Fine-grained BaTiO3-based X7R ceramic materials were prepared and the effects of milling process on the core-shell structures and dielectric properties were investigated using scanning electron microscope, transmission electron microscope, and energy dispersive spectroscopy (EDS). As the milling time extends, the dielectric constant of the ceramics increases, whereas the temperature coefficient of capacitance at 125°C drops quickly. The changes in dielectric properties are considered relevant to the micro-s...     

Influence of Ca_xSr_(1-x)(0≤x≤1) Substitution for Zn on Microwave Dielectric Properties of Li_2ZnTi_3O_8 Ceramic as Temperature Stable Materials

A temperature stable Li_2Zn_(0.95)(Sr_xCa_(1-x))_(0.05)Ti_3O_8 (0≤x≤1) ceramics were fabricated using a conventional solid-state route sintered at 1100 ℃ for 4 h.The XRD results indicate that the main phase Li_2ZnTi_3O_8 and secondary phase including Sr_xCa_(1-x)TiO_3 (0≤x≤1) solid solution and TiO_2 co-exist in composite and form a stable composite system when the (Ca_xSr_(1-x)) (0≤x≤1) substitutes for Zn of Li_2ZnTi_3O_(8 )ceramic.As x is increased from 0 to 1,the relative permittivity (ε_r) increases from 26.65 to 27.12,and the quality factor (Q×f) increases from 63 300 to 66 600 GHz.With the increased of x,the temperature coefficient of resonant frequency (τ_f) increases from 0.27 to 8.23 ppm/℃,and then decreases to 3.51 ppm/℃.On the whole,the Li_2Zn_(0.95)(Sr_xCa_(1-x))_(0.05)Ti_3O_8 (0≤x≤1) ceramics show excellent comprehensive properties of middle ε_r=25-27,higher Q×f ≥ 60000 GHz and τ_f ≤±8.5 ppm/℃.     

Phase Structure and Electrical Properties of La2O3-doped BiInO3-PbTiO3 Ceramics with High Curie Temperature

The phase structure and electrical properties of pure and La2O3-doped BiInOa-PbTiO3 (BI-PT) ceramics were studied respectively.In (1-x)BI-xPT (x=0.72-0.80) ceramics,the stability of tetragonal phase increased with increasing x,and pure perovskite structure was obtained for x=0.80 ceramics.The phase transition temperature range was between 575 ℃ and 600 ℃for x=0.72-0.80 ceramics,higher than that of PT (～490 ℃).The c/a ratio almost linearly decreased with increasing La2O3 content in x=0.80 ceramics.It is believed that Pb2+ vacancies were formed by La3+ substituting Pb2+ in La2O3-doped BI-PT ceramics.Tc shifted to lower temperature by 30 ℃/mol% La2O3.The maximum dielectric constant 8557 around 559 ℃ was exhibited in 0.5mol%-doped BI-0.80PT ceramics.La2O3-doped ceramics could be poled resulting from decreasing of c/a ratio and improving of dielectric loss and resistivity.The maximum piezoelectric coefficient d33 was 12 pC/N for 2mol%-doped BI-0.80PT ceramics.     

Effects of NaNbO3-Co2O3 Co-additive on the Properties of PZN-PZT Ceramics

NaNbO3-Co2O3 co-added PZN-PZT （PZCNNT） ceramics were prepared using conventional solid state reaction. The piezoelectric and dielectric properties were measured. The experimental results show that the addition of 0.3mo1% Co2O3 leads to low dielectric loss （tgδ） in PZCNNT ceramics and the proper addition of NaNbO3 not only improves piezoelectric properties but also decreases intensively dielectric loss and mechanical loss. The optimal ceramic having d33=310 pC/N, kp=0.59, εr=985, tgδ=0.0034, Qm=1380 was obtained.     

Small Rb~+ Doping in CaCu_3Ti_4O_(12)——A Possible Approach to Reduce Dielectric Loss

Ca1-xRbxCu3Ti4O12 （x=0, 0.01, 0.02 and 0.03） ceramics were synthesized by the sol-gel method. Doping Rb＋ reduces dielectric loss, which reaches minimum when x=0.02. By measuring properties of electrical conduction, larger leakage current density and height of grain-boundary Sehottky potential barrier （φB） were found in the doped samples, and φB became maximum when x=0.02. These results are attributed to the increase in the amount of oxygen vacancies and the formation of Cu-rich/Ti-poor grain-boundary layers, and it can be concluded that the dielectric loss in CCTO ceramic can be reduced by manipulating the composition and electrical properties of grain boundary.     

Preparation, characterizations and magnetic properties of doped barium hexaferrites BaFe12-2x Mn x Sn x O19 (x = 0.0–1.0)

A series of doped barium hexaferrites BaFe12-2xMnxSnxO19 (x = 0.0-1.0) particles were prepared by the co-precipitation/molten salt method. The particle size and crystalline of the samples BaFe12-2xMnxSnxO19 decrease with an increase in the doping amount x. When x is less than 0.8, the pure BaFe12-2xMnxSnxO19 particles with hexagonal plate morphology are obtained. The effects of substitution on magnetic properties were evaluated and compared to nomal BaFe12O19. The specific magnetizations (Ms) of doped materials have been significantly improved. Among all these compositions, the BaFe10.4Mn0.8Sn0.8O19 sample has the highest Ms value of 81.8 A?m2?kg-1 at room temperature and its intrinsic coercivity (Hc) is 44.5 kA?m-1. The as-prepared doped barium ferrites exhibit a low temperature coefficient of coercivity close to zero. The coercivity is independent of temperature when x is in the a range 0.5-0.7.     

Preparation, Characterization and Dielectric Property of Sr5 LaTi3 Nb7O30 Ceramic

Sr5LaTi3Nb7O30 ceramic was prepared by the conventional high temperature solid-state reaction route. The sintered samples were characterized by X-ray diffraction, scanning electron microscopy ( SEM ), differential thermal calorimetry ( DSC ) and dielectric measurements. The results show Sr5LaTi3Nb7O30 belongs to paraclectric phase of filled tetrngonal TB structure at room temperature, and undergoes a diffuse phase transition in the temperature range of -54-34℃ . And Sr5LaTi3Nb7O30 ceramic shows a high dielectric constant of 479 with a low dielectric loss of 0.005 at 1MHz . In comparison with Ba-based ceramics with TB structure, the temperature coefficients of the dielectric constant ( τt ) is significantly reduced.