(Ag_(0.75)Li_(0.1)Na_(0.1)K_(0.05))(Nb_(1-x)Sb_x)O_3无铅压电陶瓷的结构和电性能研究

采用传统陶瓷工艺制备了(Ag_(0.75)Li_(0.1)Na_(0.1)K_(0.05))(Nb_(1-x)Sb_x)O_3(x=0~0.10)系无铅压电陶瓷,研究了Sb含量变化对陶瓷的相结构、显微结构和电性能的影响。结果表明:在所研究组成范围内陶瓷均形成了单一钙钛矿结构,当x=0.03~0.06时陶瓷存在正交-伪立方两相共存区;Sb~(5+)的引入使陶瓷的晶粒尺寸有所减小,当x=0.04~0.06时陶瓷晶粒尺寸较为均匀(1~2μm)。陶瓷压电常数d_(33)和机电耦合系数k_p随Sb含量增加均先增大后减小,d_(33)和k_p分别在x=0.04和0.05时达到最大值68 p C/N和26.0%。Sb~(5+)的引入使陶瓷的居里温度有所降低,铁电相变得更加不稳定。     

(K0.5Na0.5)(TaxNb1-x)O3无铅压电陶瓷的性能特征

采用传统电子陶瓷制备工艺制备了(K0.5Na0.5)(TaxNb1-x)O3无铅压电陶瓷。研究了不同Ta含量下(K0.5Na0.5)(TaxNb1-x)O3陶瓷的晶相组成及性能特征。结果表明,(K0.5Na0.5)(TaxNb1-x)O3陶瓷在低Ta含量时形成单一斜方相固溶体,但Ta含量达到0.08mol后则有K6Ta10.8O30次晶相产生。随着Ta的加入,陶瓷的体积密度逐渐增大,居里温度(Tc)逐渐降低。当Ta含量为0.08mol时陶瓷具有良好的铁电、压电性能和介电稳定性能,其压电常数d33为76pC/N。     

(K0.52Na0.44Li0.04)(Nb0.86Ta0.10Sb0.04)O3-BiFeO3无铅压电陶瓷的电性能

采用固相法制备(1-x)(K0.52Na0.44Li0.04)(Nb0.86Ta0.10Sb0.04)O3-xBiFeO3[(1-x)LF4-xBF]无铅压电陶瓷,研究BF含量(0≤x≤0.010 00)对LF4陶瓷微观结构和电性能的影响.结果表明:所有样品均具有纯的四方钙钛矿结构,引入BF能明显改善LF4陶瓷的致密性...     

Ba掺杂对Pb(Zr,Ti,Sb)O_3压电陶瓷Curie温度与压电性能的影响

用传统固相法制备了组成为0.98Pb1.0–xBaxTi0.48Zr0.52O3–0.02PbSbO3(x=0.18～0.24)的Ba掺杂Pb(Zr,Ti,Sb)O3(PSZT)压电陶瓷。通过X射线衍射和Raman光谱研究了Ba掺杂PSZT陶瓷的结构,并测量和分析了Ba掺杂对PSZT压电陶瓷的Curie温度和压电性能的影响。结果表明:Ba掺杂影响PSZT陶瓷中四方相和三方相的转化过程、两相比例、晶粒大小并导致四方相的晶格畸变。随Ba含量(x)从0.18增加到0.24,PSZT陶瓷的Curie温度从189℃几乎线性下降到141℃;当Ba掺杂量为0.22时,PSZT陶瓷的Curie温度为156℃,压电应变常数d33为578pC/N,机电耦合系数Kp为0.63,机械品质因数Qm为37.3。     

Mg4(Mb2-xSbx)O9陶瓷的制备与微波介电性能

采用传统固相反应法制备了Mg4(Nb2-xSbx)O9陶瓷,研究了该材料的烧结性能、物相结构、显微组织和微波介电性能.X射线衍射结果显示,在x小于或等于1.6的范围内,形成了具有α-Al2O3刚玉型晶体结构的连续固溶体,晶轴长度和晶胞体积均随着锑含量的增加而降低.在x等于2.0时,Mg4Sb2O9的物相结构发生了变化,晶轴长度和晶胞体积也发生了突变.当0.4≤x≤O.8时,陶瓷的烧结温度从1400℃降低到了1300℃;而当x≥1.2后,陶瓷的烧结性能和微波介电性能均降低.在1300℃,5h的烧结条件下,Mg4(Nb1.6Sb0.4)O9陶瓷的微波介电常数(εr)为12.26,Q·f为168450 GHz.     

溶胶–凝胶法制备(Na0.50+xK0.50-2xLix)Nb0.9Ta0.1O3无铅压电陶瓷及其性能

采用溶胶–凝胶法制备Li+取代(K0.5Na0.5)+及Ta5+取代Nb5+的(K0.5Na0.5)NbO3陶瓷粉体,采用无压烧结工艺制备(Na0.50+xK0.50–2xLix)Nb0.9Ta0.1O3(x=0,0.02,0.04)陶瓷样品。研究了前驱体煅烧温度对陶瓷粉体物相组成的影响。分析了不同Li+掺杂量对样品物相组成、微观结构、体积密度及电学性能的影响。结果表明:前驱体的最佳煅烧温度为600℃,通过透射电子显微镜分析陶瓷粉体的粒径为49 nm;不同Li+掺杂量制备的(Na0.50+xK0.50–2xLix)Nb0.9Ta0.1O3陶瓷样品均为正交相钙钛矿结构;随着Li+掺杂量的增加,(Na0.50+xK0.50–2xLix)Nb0.9Ta0.1O3陶瓷的体积密度先增大后减小,介电常数逐渐升高,压电常数先降低再升高,剩余极化强度逐渐升高。Li+掺杂量x为0.04时样品的压电常数(d33=94 pC/N)、相对介电常数(εr=684.33)及剩余极化强度(Pr=98.27μC/cm2)较好。     

(K_(0.44)Na_(0.52)Li_(0.04))(Nb_(0.86)Ta_(0.10)Sb_(0.04))O_3陶瓷的压电性能

采用传统固相法制备Li、Ta和Sb共同掺杂铌酸钾钠(KNN)的(K0.44Na0.52Li0.04)(Nb0.86Ta0.10Sb0.04)O3(KNLNTS)无铅压电陶瓷。研究不同烧结温度对该陶瓷的结构、形貌、致密度以及电学性能的影响。结果表明:不同温度下烧结的陶瓷样品均为钙钛矿相结构;在1 050~1 150℃之间烧结均可获得性能良好的陶瓷样品;1 050℃烧结的样品表现出最佳的综合电学性能,即相对介电常数和压电系数均较大,分别为1 120pC/N和193pC/N,介电损耗较小为2.55%,机械品质因子较大为85,密度较大为4.65g/cm3,且该样品具有饱和的电滞回线。随着烧结温度的升高,陶瓷样品电学性能下降和晶粒增大均与样品中存在着碱金属离子挥发有关。KNLNTS陶瓷样品的Curie温度由不掺杂的KNN陶瓷样品的420℃下降为301℃。     

MgO掺杂Ca_(0.85)Sr_(0.15)Cu_3Ti_(4.01)O_(12)陶瓷的制备及介电性能

首先研究了Ti缺失和过量对Ca_(0.85)Sr_(0.15)Cu_3Ti_(4+x)O_(12)陶瓷粉体(x=-0.005～0.020)相结构的影响,再采用传统固相法制备了MgO掺杂(0～25 mol%)Ca_(0.85)Sr_(0.15)Cu_3Ti_(4.01)O_(12)陶瓷,主要研究了MgO含量变化对Ca_(0.85)Sr_(0.15)Cu_3Ti_(4.01)O_(12)陶瓷晶相结构、显微结构和介电性能的影响。结果表明:x=-0.005～0.005时有少量的CuO杂相存在,当x=0.010时得到了单一的类钙钛矿结构,Ti含量进一步增加出现了少量的TiO_2杂相;随着MgO掺量的增加,晶粒尺寸逐渐增大,在MgO掺量为1 mol%时,体积密度达到最大为4.98 g/cm~3,相对密度为98.76%。陶瓷的室温介电常数和介电损耗均是先增大后减小,在MgO掺量为5 mol%时,陶瓷的介电常数达到最大值1.01×10~5(10 kHz),介电损耗为0.183。在40～100 kHz频率范围内,介电常数均在4.78×10~4以上,具有良好的频率稳定性。     

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.     

Ca含量对(Ba1-xCax)(Zr0.1Ti0.9)O3-BiFeO3无铅压电陶瓷微结构和电学性能的影响

笔者采用传统固相法制备了0.99(Ba_1-xCa_x)(Zr_0.1Ti_0.9)O₃-0.01BiFeO₃(BC_xZT,x=0.00,0.06,0.12,0.18)无铅压电陶瓷,系统地研究了Ca含量对陶瓷相结构、微观形貌和电学性能的影响。研究结果表明：所有样品均为ABO₃钙钛矿结构固溶体,无其他杂相存在;随着Ca含量的增加,陶瓷晶体结构从三方相向四方相转变。Ca的加入对频率色散影响不明显,具有良好的频率稳定性。通过拟合修正后的Curie-Weiss定律,研究介电弛豫特性,γ值由1.76降到1.61,说明陶瓷弛豫程度下降。Ca取代Ba后,d₃₃和k_p均呈现先增加后减小的变化趋势,当x=0.12时获得最佳电学性能：ε_r=4 448、tanδ=0.013、d₃₃=207 pC/N、k_p=0.24。从P-E曲线观察出...     

Nonstoichiometric microwave dielectric ceramics [(Na0.5-xBi0.5+x/3)0.5Ca0.5]MoO4 with low sintering temperatures

In this work, [(Na_0.5-xBi_0.5+x/3)_0.5Ca_0.5]MoO₄ (x = ±0.03, ±0.06, ±0.09, ±0.12) microwave dielectric ceramics prepared by the solid-state reaction method are investigated. All the samples can be sintered well below 800℃. The sintered ceramics show a scheelite structure without any secondary phase, indicating that a solid solution is formed in nonstoichiometric [(Na_0.5-xBi_0.5+x/3)_0.5Ca_0.5]MoO₄. While x value increases from -0.12 to 0.12, the relative permittivity rises from 16.7 to 21.0, TCF value is improved from -21 ppm/℃ to +1 ppm/℃, and Q × f value varies in the range of 17,000 GHz and 34,000 GHz. The Raman analysis reveals that one of the external modes is attributed to be the main factor affecting the performances. When x = 0.09 and 0.12, high performance microwave dielectric ceramics can be well densified at low sintering temperatures (750−775℃) with relative permittivities of 20.9–21.0, improved Q × f values of 31,400−33,000 GHz, and near-zero temperature coefficients of resonate frequency (|TCF| ≈ ±2 ppm/℃).     

Effect of Sn Substitution on Cation Ordering in (Zr1–xSnx)TiO4 Microwave Dielectric Ceramics

The crystal structure and microwave dielectric properties of (Zr_1–xSn_x)TiO₄ ceramics with x ranging from 0.0 to 0.15 have been investigated to characterize the effect of Sn substitution on cation ordering and the effect of ordering on dielectric loss. The crystal structure of the samples was investigated using high-resolution transmission electron microscopy and electron diffraction. Although Sn substitution inhibits ordering, the effect is progressive and ordering still proceeds to an observable degree in samples with x = 0.15. The ordered structure of all samples is of the incommensurate modular type previously observed for Sn-free zirconium titanate compositions. In this structure individual (100) cation layers are observed to switch abruptly from Zr-rich to Ti-rich occupancy, indicating that ordering proceeds by the segregation of Zr and Ti into elongate two-dimensional domains on (100). The domains get smaller as the Sn content of the samples increases and in Zr_0.5Sn_0.15TiO₄ the length scale of the cation correlations is approximately 25–50 Å. We propose that the decrease in the driving energy for the coarsening of the domains during the ordering transformation is due to the preferential segregation of Sn to the Zr-Ti domain boundaries. Whereas the long-range cation ordering increases the dielectric loss of Sn-free ceramics by 30%, it results in a negligible change in the loss properties of Zr_0.91Sn_0.09TiO₄. It is possible that the hypothesized effect of Sn in stabilizing the Zr-Ti boundaries may also affect the contribution of these sites to the dielectric loss of the ordered structures.     

Phase Structure, Microstructure, and Electrical Properties of Sb-Modified (K, Na, Li) (Nb, Ta) O3 Piezoelectric Ceramics

Lead-free (K_0.44Na_0.52Li_0.04)(Nb_{0.80− x} Ta_0.20Sb _x )O₃ piezoelectric ceramics were prepared by the ordinary sintering method. The much higher Pauling electronegativity of Sb compared with Nb makes the ceramics more covalent. By increasing x from 0.00 to 0.06, the phase structure of the ceramics changed from the tetragonal to the pseudocubic phase, and both the bands in the Raman scattering spectra shifted to lower frequency numbers. The grain growth of the ceramics was improved by substituting Sb⁵⁺ for Nb⁵⁺. By increasing x , the dielectric properties were optimized and the variation of dielectric constants before and after poling became smaller. Only the tetragonal–cubic phase transition was observed above room temperature in all the ɛ_r– T curves. The degree of diffuseness increased from 1.29 at x =0.00 to 1.96 at x =0.06, indicating that the ceramics at x =0.06 changed to an approximate ideal relaxor ferroelectric. The temperature dependences of f _r and k _p became better by increasing x properly. Significantly, the ceramics with x between 0.00 and 0.04 had high density and outstanding electrical properties ( d ₃₃=241–272pC/N, k _p=0.42–0.52, ɛ_r=1258–1591, tan δ=0.015–0.025, T _c=280°–355°C, E _c=10.62–12.60 kV/cm, and P _r=16.19–20.13 μC/cm²). Besides, the underlying mechanism for variations of the electrical properties due to Sb⁵⁺ substitution was explained in this work.     

复合烧结助剂对Ca_(0.3)(Li_(0.5)Sm_(0.5))_(0.7)TiO_3微波介质陶瓷低温烧结与性能研究

研究了以Ca_(0.3)(Li_(0.5)Sm_(0.5))_(0.7)TiO_3(CLST-0.7)为基料,复合添加10 wt%CaO-B_2O_3-SiO_2(CBS)、4 wt%Li_2O-B_2O_3-SiO_2-CaO-Al_2O_3(LBSCA)和0～2 wt%CuO氧化物为烧结助剂的微波介质陶瓷的低温烧结行为及微波介电特性.结果表明:随着CuO添加量的增加,陶瓷体积密度、介电常数ε_r、无载品质因数与谐振频率乘积Qf值,都呈先增加后降低,频率温度系数τ_f呈降低的趋势.添加10 wt%CBS、4.0 wt% LBSCA和1.0 wt%CuO的CLST-0.7微波介质陶瓷,在900 ℃烧结5 h具有较佳的微波介电性能:ε_r ＝ 67.31,Qf ＝ 2197 GHz,τ_f＝40.28 ppm/℃.     

Preparation and Properties of （Na0.50＋xK0.50-2xLix）Nb0.9Ta0.1O3 Lead-Free Piezoelectric Ceramics by Sol-Gel Method

采用溶胶–凝胶法制备Li＋取代（K0.5Na0.5）＋及Ta5＋取代Nb5＋的（K0.5Na0.5）NbO3陶瓷粉体,采用无压烧结工艺制备（Na0.50＋xK0.50–2xLix）Nb0.9Ta0.1O3（x=0,0.02,0.04）陶瓷样品。研究了前驱体煅烧温度对陶瓷粉体物相组成的影响。分析了不同Li＋掺杂量对样品物相组成、微观结构、体积密度及电学性能的影响。结果表明：前驱体的最佳煅烧温度为600℃,通过透射电子显微镜分析陶瓷粉体的粒径为49nm;不同Li＋掺杂量制备的（Na0.50＋xK0.50–2xLix）Nb0.9Ta0.1O3陶瓷样品均为正交相钙钛矿结构;随着Li＋掺杂量的增加,（Na0.50＋xK0.50–2xLix）Nb0.9Ta0.1O3陶瓷的体积密度先增大后减小,介电常数逐渐升高,压电常数先降低再升高,剩余极化强度逐渐升高。Li＋掺杂量x为0.04时样品的压电常数（d33=94pC/N）、相对介电常数（εr=684.33）及剩余极化强度（Pr=98.27μC/cm2）较好。     

Structural and Dielectric Properties of Ag(Nb0.8Ta0.2)1−xSbxO3 (x≤0.08) Ceramics

Sb₂O₅ were selected to substitute (Nb_0.8Ta_0.2)₂O₅ and the effects of Sb substitution on the dielectric properties of Ag(Nb_0.8Ta_0.2)O₃ ceramics were studied. The perovskite Ag(Nb_0.8Ta_0.2)_{1− x} Sb _x O₃ ceramics showed no obvious change with x value being no more than 0.08, and the pseudoperovskite unit cell parameters a = c , b and monoclinic angle β decrease with Sb concentration increasing. The dielectric properties of Ag(Nb_0.8Ta_0.2)_{1− x} Sb _x O₃ ceramics were found to be affected greatly by the substitution of Sb for Nb/Ta. The ɛ value of Ag(Nb_0.8Ta_0.2)_{1− x} Sb _x O₃ ceramics sintered at their densified temperature increased from 480 to 825 with x from 0 to 0.08, the tan δ value decreased sharply from 0.0065 to 0.0023 (at 1 MHz) with x increasing from 0 to 0.04, and then kept a stable lower tan δ value ∼0.0024 with x to 0.08. The temperature coefficient of capacitance values continuously decreased from a positive value of 1450 ppm/°C for x =0 to a negative value of −38.52 ppm/°C for x =0.08.     

BNBMT无铅压电陶瓷的制备及性能研究

本文采用新型溶胶-凝胶制粉技术和传统陶瓷生产工艺制备了0.93Bi0.5Na0.5TiO3-0.07Ba1-xMgxTiO3（简称BNBMT100x）体系无铅压电陶瓷,并对BNBMT陶瓷的晶相特征及其介电和压电性能进行了讨论。XRD分析表明,陶瓷样品均形成了单一的钙钛矿结构固溶体;Mg的加入对陶瓷的介电、压电性能有显著影响;陶瓷的铁电-顺电相变峰显著降低、展宽;介电损耗在室温至200℃范围内较平缓。当x=0.04时,机电耦合系数kp和kt最大,分别为16%和19%,压电常数d33值为111pC/N。