Electrical,structural and thermal properties of nanoceramic (Bi2O3)1−x−y(Ho2O3)x(Tm2O3)y ternary system

Ho₂O₃ and Tm₂O₃ doped Bi₂O₃ composite electrolyte type materials for solid oxide fuel cells (SOFCs) operating at intermediate-temperature were investigated. The bismuth-based ceramic powders were produced by using conventional solid-state synthesis techniques. The products were characterized by means of scanning electron microscopy (SEM), X-ray powder diffraction (XRD), differential thermal analysis/thermal gravimetry (DTA/TG), and the four-point probe technique (4PPT). XRD and DTA/TG measurements indicate that all of the samples have the stable fluorite type face centered cubic (fcc) δ-phase. 4PPT measurements were performed in the temperature range 150–1000 °C in air and these measurements showed that the electrical conductivity of the samples decrease with increasing amount of Tm₂O₃. This increase in the electrical conductivity of the samples could be attributed to the increase in the numbers of highly polarizable cations and oxide ion vacancies. The highest conductivity value was found as 5.31×10^?1 Ω cm^?1 for the (Bi₂O₃)_1?x?y(Ho₂O₃)_x(Tm₂O₃)_y ternary system (for x=20 and y=5 mol%) at 1000 °C. The activation energies of the samples were calculated from log σ graphics versus 1000/T. These calculated results showed that the translation motion of the charge carriers, oxygen vacancies, and space charge polarizations are responsible for the change in activation energy as a function of temperature.     

Li_2O掺杂Li_(3x)La_(2/3-x)TiO_3固体电解质的制备及性能

用高温固相法合成了一系列不同组成的固体电解质Li3xLa2/3-xTiO3(LLTO,x=0.06,0.10,0.12,0.16,摩尔分数),研究了不同Li2O掺杂量对LLTO显微结构和电导率的影响。对样品进行X射线衍射和扫描电子显微镜分析,用交流阻抗技术测试其电导率。结果表明:LLTO为超结构的立方晶体,在LLTO(x=0.12)陶瓷中有Li0.485La0.505TiO3相产生;1150℃烧结的样品晶粒分布较均匀且大部分为球形,1250℃烧结的样品致密度较高,晶粒的形状均匀,为片状,x=0.06时,LLTO的电导率最大,其室温电导率为1.1×10-6S/cm。     

New Gallium-substituted hydrotalcites: [Mg1-x Ga x (OH)2](CO3) x/2 ·mH2O

A series of Ga-containing hydrotalcite-like materials (GaHTs), [Mg_1-x Ga _x (OH)₂](CO₃) _x/2 ·mH₂O wherex = 0.072 0.35 (Mg/Ga = 12.9 1.8), was synthesized by a coprecipitation method. The resulting solids were characterized by means of X-ray diffraction, thermal gravimetric and infrared analyses. All GaHTs showed diffraction patterns typical of Mg-Al hydrotalcites. Small amounts of brucite, Mg(OH)₂, were detected only in the GaHT with Mg/Ga = 12.9. Attempts to obtain Ga-richer hydrotalcites, Mg/Ga < 1.8, resulted in solids with an invariably constant Mg/Ga = 1.8 ratio, which appears to be the maximum Ga content limit. Judging from the TGA pattern of a GaHT (Mg/Ga = 7.7), the layered structure is stable up to ca. 573 K, and at 873 K the resulting solid shows a MgO-like diffraction pattern, suggesting that Ga³⁺ may be replacing some Mg²⁺ ions in MgO. Once their layered structure collapses (i.e., at 873 K), GaHT can be easily converted back into the original layered material by treating in a carbonate-containing aqueous solution, i.e., they show the memory effect typical of Mg-Al hydrotalcites.     

Linear Optical Properties of x PbO – 20 SiO2–10 Na2O – (70 - x) B2O3 Glass System

Silicon - Optical spectral analysis of a glass system with composition xPbO – 20 SiO2–10 Na2O – (70 - x) B2O3, where x = 20, 30, 40, 50 and 60 mol %, was studied. The investigated...     

A comparative raman study of the local structure in (Ge2S3) x (As2S3)1-x and (GeS2) x (As2S3)1−x glasses

The Raman spectra of glasses in the ternary (Ge₂S₃) _x (As₂S₃)_1−x and (GeS₂) _x (As₂S₃)_1−x systems are reported. It is shown that the degree of disorder in the (Ge₂S₃) _x (As₂S₃)_1−x glasses increases with an increase in the Ge content. The differences in the spectra of glasses with the same molar content of As₂S₃ are discussed in terms of the changes occurring in the local structure due to deviations from the stoichiometry. The observed changes in the intensity of the boson peak indicate changes in the medium-range order structure of the glasses under study.     

高Curie温度(1-2x)PbNb2O6-xSrTiO3-xTiO2压电陶瓷

采用传统电子陶瓷的制备方法制备了(1-2x)PbNb2O6-xSrTiO3-xTiO2(x=0.005～0.025)高Curie温度(θc)压电陶瓷.X射线衍射分析表明:所有样品在1 250℃保温2h烧结均形成铁电性的斜方钨青铜型结构(tungsteu bronze structure,TB).相对介电常数-温度(εr-θ)曲线表明:该体系具有高的θc(500～560℃).测试了不同掺杂量对陶瓷介电和压电性能的影响,发现材料的θc、压电常数(d33)和机电耦合系数(κp)随着x值的增加先增加后降低.当x=0.02时,陶瓷的d33达到最大值,为83pC/N,θc为550℃,κp达33.4%,材料的介电常数Εθ33/ε0为217,为组成的最优配方.     

Ceramic pigments from CoxNi3-xP2O8 (0 ≤ x ≤ 3) solid solutions

Co_xNi_3-xP₂O₈ (0 ≤ x ≤ 3) solid solutions were synthesized via the chemical co-precipitation method. Variation of unit cell parameters and interatomic distances indicated that these solid solutions with the Ni₃P₂O₈ structure are stable between 800 and 1200 °C in compositions with 0 ≤ x ≤ 1.5 and between 800 and 1000 °C when (0 ≤ x ≤ 3). When (2.5 ≤ x ≤ 3.0), the solid solutions lead to the Co₃P₂O₈ structure, being stable between 800 and 1000 °C.The yellow colour of the Ni₃P₂O₈ compound changes to pink or red when Co(II) ions are incorporated in the structure as Ni₃P₂O₈ solid solutions are formed. Bands corresponding to second and third electronic transitions of the Co(II) ions in octahedral coordination appear in the 450–600 nm in the UV-V spectra, and they are responsible of the observed changes in the colour. Absorbance in the visible spectra was also obtained from enamelled samples but a new band at 650 nm with considerable absorbance when x > 1.0 increased the blue amount, and colour of the enamelled samples was yellowish brown, brown, green and blue.     

Dielectric properties of (1−x)La(Mg1/2Ti1/2)O3–xSrTiO3 ceramics

Powders of (1−x)La(Mg_1/2Ti_1/2)O₃–xSrTiO₃ series have been prepared by a non-conventional chemical route based on the Pechini method. Homogeneous solid solutions allowed the sintering of dense and single-phase ceramics for the full composition range (0⩽x<1). Crystal structure of the ceramics was investigated by XRD and several compositional driven structural transformations were observed. The dielectric function of the ceramics was measured at radio, microwave and far infrared (FIR) frequency ranges to help clarifying the relationship between dielectric properties and structure. The FIR data were found to reflect clearly the sequence of structural modifications observed. In order to evaluate the importance of intrinsic mechanisms in the dielectric response at the GHz and MHz ranges, the reflectivity spectra were fit to the Berreman–Unterwald form of dielectric function. The fits showed that the lower frequency dielectric response seems to be dominated by lattice phonons. Microwave permittivity and temperature coefficient of the resonant frequency were found to obey a hyperbolic-type law.     

Large-strain 0.7Pb(ZrxTi1−x)O3–0.1Pb(Zn1/3Nb2/3)O3–0.2Pb(Ni1/3Nb2/3)O3 piezoelectric ceramics for high-temperature application

0.7Pb(Zr_xTi_1−x)O₃–0.1Pb(Zn_1/3Nb_2/3)O₃–0.2Pb(Ni_1/3Nb_2/3)O₃ (0.7PZT–0.1PZN–0.2PNN, x = 0.44–0.47) piezoelectric powders and ceramics have been prepared through conventional solid-state reaction method. Outstanding piezoelectric and dielectric properties occurred at the morphotropic phase boundary (MPB), which was characterized by the X-ray diffraction spectrum. The MPB composition (x = 0.46) performed high d₃₃ value (641 pC/N), indicating that the system suited large-strain application. The field-induced strain reached 0.25% under a considerably low electric field (0.8 kV/mm) according to the bipolar strain *S–E loops. The effect of the grain size on the aging phenomenon and temperature stability has also been investigated. Due to higher Curie temperature and smaller grain size, the 0.7PZT–0.1PZN–0.2PNN ceramics maintained a high d₃₃ level after depoling treatment, revealing a superior strain capacity for high-temperature application.     

Effects of microstructure on the microwave dielectric properties of Ba(Co1/3Nb2/3)O3 and (1−x)Ba(Co1/3Nb2/3)O3–xBa(Zn1/3Nb2/3)O3 ceramics

Ba(Co_1/3Nb_2/3)O₃(BCN) has a 1:2 ordered hexagonal structure. A large amount of the liquid phase, which contains high concentrations of Ba and Nb ions was found in the BCN ceramics. Q-values of BCN increased with increasing sintering temperature; however, it significantly decreased when the sintering temperature exceeded 1400 °C. The presence of a large amount of liquid phase could be responsible for the decrease of the Q-value. For (1−x)Ba(Co_1/3Nb_2/3)O₃–xBa(Zn_1/3Nb_2/3)O₃ [(1−x)BCN–xBZN] ceramics, the 1:2 ordered hexagonal structure was observed in the specimens with x⩽0.3 and the BaNb₆O₁₆ second phase was found in the specimens with x⩾0.6. Grain growth, which is related to the BaNb₆O₁₆ second phase occurred in the specimens with x⩾0.5. In this work, the excellent microwave dielectric properties of τ_f=0.0 ppm/°C, ε_r=34.5 and Q×f=97,000 GHz were obtained for the 0.7BCN–0.3BZN ceramics sintered at 1400 °C for 20 h.     

添加Al2O3-ZrO2(Y2O3)系易熔混合物的Al2O3质陶瓷

研制了添加Al2O3—ZrO2(Y2O3)系易熔混合物细粉碎颗粒的刚玉质陶瓷，并研究其结构和性能。指出利用这种易熔混合物对于制造陶瓷材料是很有前途的。     

Li_(1+x)Ge_(2-x)Cr_xP_3O(12)系统的相关系与电导

研究了Li_(1+x)Ge_(2-x)Cr_xP_3O_(12)系统的相组成与电导的关系。用Cr~(3+)置换LiGe_2P_3O_(12)中的Ge~(4+)在00.5时出现未知相。用少量Cr~(3+)取代Ge~(4+)后电导率即骤增,在固溶体范围内电导率随x值的增大而升高,在0.2≤x≤0.6区间都有较高的电导率。Lj_(1.3)Ge_(1.7)Cr_(0.3)P_3C在35℃、300℃、450℃时的电导串分别为2.9×10~(-5)、1.1×10~(-2)、4.6×10~(-2)(S/cm),电导活化能为0.37eV,电子迁移数在10~(-5)数量级。     

Phase Formation in the ZrO2 – Nd2O3 (Y2O3) – Al2O3 (Cr2O3) SYSTEMS AND PROPERTIES OF MATERIALS BASED ON THEM

The nature and degree of completeness of phase transformations that occur at 1100 – 1750°C in ZrO₂ – Nd₂O₃ (Y₂O₃) – Al₂O₃ (Cr₂O₃) compositions rich with ZrO₂ are studied. It is shown that the zirconium-yttrium cubic solid solution has a maximum resistance to the action of Al₂O₃ and Cr₂O₃. The sinterability and other properties of parts from ZrO₂ can be controlled within a quite wide range by adding Al₂O₃, Cr₂O₃, and NdCrO₃ to ZrO₂ stabilized by Nd₂O₃.     

Crystal structure and piezoelectric properties of xPb(Mn1/3Nb2/3)O3–(0.2 − x)Pb(Zn1/3Nb2/3)O3–0.8Pb(Zr0.52Ti0.48)O3 ceramics

Pb(Mn_1/3Nb_2/3)O₃–Pb(Zn_1/3Nb_2/3)O₃–Pb(Zr_0.52Ti_0.48)O₃ (designated as PMnN–PZN–PZT) piezoelectric ceramics were prepared and the effects of PMnN content on the crystal structure and electrical properties were investigated. The results show that the pure perovskite phase forms in these ceramics. The crystal structure changes from tetragonal to rhombohedral and the lattice constant decreases with increase of PMnN content. The morphotropic phase boundary (MPB) of xPMnN–(0.2 ? x)PZN–0.8PZT ceramics occurs where the content of PMnN, x, lies between 0.05 and 0.085 mol. The dielectric constant (?), piezoelectric constant (d₃₃) and Curie temperature (T_c) decrease, while the mechanical quality factor (Q_m) increases with the increase of PMnN content. The ceramic with composition 0.075PMnN–0.125PZN–0.8PZT has the optimal piezoelectric properties, ? is 842, d₃₃ is 215 pC/N, T_c is 320 °C, k_p is 0.57 and Q_m amounts to 1020, which makes it a promising material for high power piezoelectric devices.     

Na_3Zr_(2-x)Mg_xSi_(2-2x)P_(1+2x)O_(12)系统的相关系和电性能

研究了Na_3Zr_(2-x)Mg_xSi_(2-2x)P_(1+2x)O_(12)系统的组成、结构和电性能。结果表明:Mg~(2+)能在一定的组成范围内取代Na_3Zr_2Si_2PO_(12)中的Zr~(4+)形成固溶体,单相固溶体区域延伸至x=0.5;当x=0.4时固溶体的结构由单斜转变为三方。固溶体的电导率随x的增加而降低。本文还从结晶化学的角度讨论了Na_3Zr_(2-x)Mg_xSi_(2-2x)P_(1+2x)O_(12)系统的组成、结构和电性能的关系。     

Ba1-3x/2Lax(Mg1/3Ta2/3)O3陶瓷的微波介电性能

采用固相合成法制备了Ba1-3x/2Lax(Mg1/3Ta2/3陶瓷,研究了La掺杂对钽镁酸钡的结构和微波介电性能的影响.结果表明:A位取代能改进其烧结性能.在x≤0.02时,烧结样品为单相的钙钛矿结构,B位离子1:2有序;当x>0.02时出现第二相Ba0.5TaO3.B位离子有序度随着x的增大先增加后减小,在x=0.04时出现最大值.x≤0.02时介电常数变化较小,而后其值逐渐增大.品质因数与谐振频率的乘积(Q×f)值随着x的增大先增大后减小,在x=0.02时取得最大值;谐振频率温度系数(τf)值随着x增大而增大.     

(1-y)Ca1-xLa2x/3TiO3-yCa(Mg1/3Nb2/3)O3复合微波介质陶瓷的研究

采用固相合成法制备了 ( 1-y)Ca1 -xLa2x/ 3 TiO3 -yCa(Mg1 / 3 Nb2 / 3 )O3 系列微波介质陶瓷材料 ,研究了复合系统的微波介电性能、烧结性能和微观结构。研究结果表明 :在y =0 .4～ 0 .6范围内 ,体系形成了单一的钙钛矿结构 ;当复合体系组成 0 .5Ca0 .6La0 .2 67TiO3 -0 .5Ca(Mg1 / 3 Nb2 / 3 )O3 时 ,在 14 0 0℃下烧结保温 4小时所得到材料的微波介电性能最佳 ;εf=5 5 ,Q×f =45 0 0 0GHz( 7.6GHz下 ) ,τf=0 .0 4ppm/℃。     

(1-y)Ca1-xLa2x/3TiO3-yCa(Mg1/3Nb2/3)O3复合体系的微波介电性能

采用固相合成法制备了(1-y)Ca1-xLa2x/3TiO3-yCa(Mg1/3Nb2/3)O3系列微波介质陶瓷材料.研究了复合系统的微波介电性能和微观结构.研究结果表明在y=0.4～0.6范围内,体系形成了单一的钙钛矿结构.当复合体系组成为0.5Ca0.6La0.267TiO3-0.5Ca(Mg1/3·Nb2/3)O3时,在1 400℃下烧结保温4 h所制备的材料表现出良好的微波介电性能εr=55,Q×f=45 000 GHz(7.6 GHz下),τf=0.04×10-6/℃.     

Li_(1 x)Ti_(2-x)Ga_xP_3O_(12)和Li_(1 2x)Ti_(2-x)Mg_xP_3O_(12)系统的相关系和电导

研究了Li_(1 x)Ti_(2-x)Ga_xP_3O_(12)和Li_(1 2x)Ti_(2-x)Mg_xP_3O_(12)系统的组成、结构和电性的关系。在这两个系统中,Ga~(3 )和Mg~(2 )都能在一定的组成范围内取代LiTi_2P_3O_(12)中的Ti~(4 )形成固溶体,并使电导率提高。电导率极大值分别出现在x=0.6和x=0.3处,其在300℃左右的值为8.4×10~(-3)和5.3×10~(-3)s/cm。 比较了Ga~(3 )、Mg~(2 )和In~(3 )三种离子取代Ti~(4 )对电性的影响,并从结晶化学角度讨论了它们的差异。