Bi0.5Na0.5TiO3和Bi0.5K0.5TiO3含量对三元固溶体系无铅PTC热敏陶瓷性能的影响

PTC热敏陶瓷的无铅化是绿色智能加热及电路智能保护元件研制的重要前提。为了获得可在空气气氛下烧结且兼具高居里温度和高升阻比的无铅化PTC热敏陶瓷,本工作采用固相法制备了(1-x)BaTiO₃-0.5xBi_0.5Na_0.5TiO₃-0.5xBi_0.5K_0.5TiO₃和0.98BaTiO₃-0.02yBi0_.5Na_0.5TiO₃-0.02(1-y)Bi_0.5K_0.5TiO₃三元固溶体系无铅PTC热敏陶瓷材料,研究了不同含量的Na和K元素对无铅PTC热敏陶瓷材料的烧结特性和电学性能的影响。结果表明,BNT和BKT均与BaTiO₃形成固溶体,随着BNT含量的增加,PTC陶瓷平均晶粒尺寸减小;当BNT和BKT含量相同时,PTC陶瓷可以在较宽的烧结温度范围内实现半导化,且在...     

Structure and electrical properties of (Bi0.5Na0.5)0.94Ba0.06TiO3–Bi0.5(Na0.82K0.18)0.5TiO3–BiAlO3 lead free piezoelectric ceramics

0.09(Bi_0.5Na_0.5)_0.94Ba_0.06TiO₃–(0.01 − x) Bi_0.5(Na_0.82K_0.18)_0.5TiO₃–x BiAlO₃ (BNBKT–xBA) lead-free piezoelectric ceramics were synthesized by conventional solid-state reaction processes. Structure, ferroelectric and piezoelectric properties of BNBKT–xBA ceramics were investigated. X-ray diffraction data shows that BNBKT–xBA ceramics form the pure perovskite phases and the ceramics have the morphotropic phase boundary when x ≤ 0.030. At room temperature, the BNBKT–xBA ceramics at x = 0.030 have better electrical properties, the piezoelectric constant d₃₃ and planar coupling factor k_p of BNBKT–xBA ceramics reaches peak values at x = 0.030: d₃₃ = 217 pC N⁻¹, k_p = 0.308. The remnant polarization P_r, mechanical quality factor Q_m and relative dielectric constant ?_r of BNBKT–xBA ceramics at x = 0.030 attains 33.8 μC cm⁻², 133 and 928 (100 KHz), respectively. As BA content increase, the depolarization temperature T_d shift toward lower temperature, and T_d of BNBKT–xBA ceramics with x = 0.030 decreased to 55 °C.     

Densification behavior, microstructure, and electrical properties of sol–gel-derived niobium-doped (Bi0.5Na0.5)0.94Ba0.06TiO3 ceramics

Superfine powders (~100 nm) with compositions of (1 − x)(Bi_0.5Na_0.5)_0.94Ba_0.06TiO₃ + xNb⁵⁺ (BNTBT6 + xNb) with x from 0 to 0.02 were synthesized by an improved citrate sol–gel method using Nb₂O₅ as Nb⁵⁺ source. The sintering behavior, microstructure, and various electrical properties of BNTBT6 + xNb ceramics were investigated. The results indicated that the addition of a small amount of Nb⁵⁺ has no remarkable effect on the crystal structure and grain morphology, but the electrical properties of the ceramics are obviously influenced. The BNTBT6 + 0.005Nb compositions exhibit enhanced densification behavior and improved electrical properties of a piezoelectric constant d ₃₃ ~ 205 pC/N and a planar electromechanical coupling factor k _p ~ 33%.     

Y2O3掺杂(Bi0.5 Na0.5)0.94 Ba0.06 TiO3无铅压电陶瓷的研究

采用固相合成法制备了Y2O3掺杂(Bi0.5 Na0.5)0.94 Ba0.06 TiO3无铅压电陶瓷.研究了Y2O3掺杂对(Bi0.5 Na0.5)0.94Ba0.06 TiO3陶瓷晶体结构、介电与压电性能的影响.XRD分析表明,在所研究的组成范围内陶瓷均能够形成纯钙钛矿固溶体.介电常数-温度曲线显示陶瓷具有弛豫铁电体特征,陶瓷的弛豫特征随掺杂的增加更为明显.在Y2O3掺杂量为0.5%时陶瓷的压电常数d33分别为137 pC/N,为所研究组成中的最大值,掺杂量为0.1%时,机电耦合系数kp与kt最大值为0.30,0.47.     

Effects of ball milling on microstructure and electrical properties of sol–gel derived (Bi0.5Na0.5)0.94Ba0.06TiO3 piezoelectric ceramics

A citrate sol–gel method was investigated for synthesizing lead-free piezoelectric compositions of (Bi_0.5Na_0.5)_0.94Ba_0.06TiO₃ (BNT) and the effect of ball milling on the sintering, microstructure and electrical properties of BNT ceramics was emphasized. The thermal analysis and X-ray diffraction results show that crystalline powders with a single perovskite structure can be obtained when calcined at 600 °C for 3 h. The average particle size of as-calcined powder and electrical properties of sintered samples were obviously dependent on an additional ball milling. Because of well-dispersed superfine powders (∼100 nm), the BNT ceramics can be well densified at temperature 50 °C lower than that by mixed-oxide method and conventional sol–gel method and as a result exhibit enhanced electrical properties of a piezoelectric constant d₃₃ ∼ 180 pC/N and a planar electromechanical coupling factor k_p ∼ 0.29.     

Tb掺杂LaMnO3材料的电输运与介电性能研究

采用固相反应法制备了A位掺杂的La0.95Tb0.05MnO3(LTMO)钙钛矿材料。研究了LTMO的电输运性能、磁性能以及介电性能。结果表明,LTMO表现出半导体电输运特性,其磁序结构表现出类自旋玻璃行为,而其介电性能在100K附近表现出弛豫特性,当温度高于100K时LTMO介电常数ε′随温度的升高几乎不变化,表现出介电常数的高温稳定性。     

半化学法制备0.80Pb(Mg1/3Nb2/3)O3-0.20PbTiO3 陶瓷的研究

研究了制备纯钙钛矿相0．80Pb(Mg1／3Nb2／3)O3-0．20PbTiO3(缩写为PMNT)陶瓷的半化学法新工艺．详细讨论了除Nb2O5外，其它反应物以其非氧化物形态分别代替PbO、MgO和TiO2，以及PbTiO3或同成分的0．80PMN-0．20PT等钙钛矿相子晶对PMNT预烧粉体中钙钛矿相含量的影响；探讨了烧结温度对半化学法制备的PMNT陶瓷介电性能的影响，并对PMNT陶瓷的相组成、显微组织及介电性能进行了表征和测定．结果表明：提高镁组分的反应活性对提高预烧粉体中钙钛矿相含量的效果较好，同时以钛酸四丁酯取代TiO2的效果最好；半化学法工艺简单，能在850。C／2h预烧条件下制得几乎纯钙钛矿相的PMNT粉体，经过较低的烧结温度(950℃／2h)可制得致密的、介电性能优异的PMNT陶瓷．     

脉冲电流烧结掺杂Ba0.5Sr0.5TiO3陶瓷介电性能的研究

以硝酸钡、硝酸锶、钛酸四丁脂、硝酸铜、硝酸镧以及氨水为原料，利用柠檬酸一硝酸盐燃烧法制备了Ba0．5Sr0．5TiO3(BST)、1mol％Cu^2 掺杂BST、1mol％La^3 掺杂BST，以及0．5mol％Cu^2 和0．5mol％La^3 共掺杂BST粉末．利用脉冲电流(简称PECS)烧结设备烧结所制备的粉体，结果发现掺杂可以大大改善BST陶瓷晶粒大小的均匀性．介电性能测试结果表明1mol％Cu^2 掺杂不仅降低了BST的介电损耗，同时也降低了介电常数，而1mol％La^3 掺杂，以及0．5mol％Cu^2 和0．5mol％La^3 共掺杂降低了BST的介电损耗，但在25℃附近介电常数升高．     

(Na0.8K0.2)0.5Bi0.5TiO3陶瓷的介电压电性能

研究了(Na0.8K0.2)0.5Bi0.5TiO3陶瓷的介电和压电性能,发现陶瓷从室温到500℃温度范围的介电谱中存在两个介电峰,电滞回线显示第一个介电峰由铁电-反铁电相变引起的,温度继续升高,反铁电相由宏畴变为微畴,微畴向顺电相转变导致了第二个介电峰,该峰对应的相变为弥散型相变.室温下陶瓷具有较高的剩余极化强度Pr=29.4μC/cm2和相对低的矫顽电场Ec=2.8kV/mm,极化后的陶瓷显示出较高的压电常数d33=120pC/N和机电耦合系数Kp=28.5%,以及高的频率常数Nφ=2916Hz.m,120℃具有最小的谐振频率温度系数.     

微波烧结BaZrxTi1-xO3陶瓷介电性能研究

采用微波烧结制备BaZrxTi1-xO3陶瓷并与常规烧结作对比,研究了微波烧结对材料晶体结构和介电性能的影响。结果表明,微波烧结在所需时间远远低于常规烧结的情况下,得到的样品在结晶度上明显优于常规烧结,微波烧结得到的陶瓷晶粒尺寸较常规烧结明显减小;介电温谱测试表明微波烧结所得陶瓷样品居里峰的峰强和峰宽都有所改变,此外,微波烧结得到的陶瓷弛豫现象也较常规烧结发生改变。     

Ferroelectric and piezoelectric properties of [(Bi0.98La0.02Na1?xLix)0.5]0.94Ba0.06TiO3 lead-free ceramics

Lead-free ceramics [(Bi_0.98La_0.02Na_1−x Li _x )_0.5]_0.94Ba_0.06TiO₃ have been prepared by an ordinary sintering technique and their ferroelectric and piezoelectric properties have been studied. The results of X-ray diffraction reveal that Li⁺, Ba²⁺, and La³⁺ diffuse into the Bi_0.5Na_0.5TiO₃ lattices to form a new solid solution with a pure perovskite structure. The partial substitution of Li⁺ lowers the coercive field E _c and improves the remanent polarization P _r. Because of the larger P _r and lower E _c, the ceramic with x = 0.10 exhibits optimum piezoelectric properties: d ₃₃ = 212 pC/N and k _P = 36.1%. The partial substitution of Li⁺ for Na⁺ shifts the depolarization temperature T _d toward low temperature. The ceramics exhibit relaxor characteristic, which is probably resulted from the cation disordering in the 12-fold coordination sites. The temperature dependences of the ferroelectric and dielectric properties suggest that the ceramics contain both the polar and non-polar regions near/above T _d, which cause the polarization hysteresis loop become deformed and the ceramics become depolarized.     

La,Nb复合掺杂Sr2Ta2O7陶瓷高温介电性能研究

研究了La,Nb复合掺杂Sr2Ta2O7陶瓷的高温介电性能,A位镧掺杂提高了材料体系的电阻活化能,从而提高了高温电阻率,Sr1.98 La0.02Ta2O7在700℃电阻率为3.65×107,和Sr2Ta2O7相比(4.37×106)电阻率提高了一个数量级;Nb掺杂对Sr2Ta2O7结构影响不大,Nb取代Ta的位置后主要影响垂直于Ta-O线的O离子位移.铌掺杂有效地提高了材料体系的居里温度,从-173℃(Sr2Ta2O7)提高到-11℃(Sr1.98 La0.02Ta1.9Nb0.1O7).     

Nb或La掺杂的Ba(Ti0.9Sn0.1)O3基陶瓷的介电性能

研究了掺杂Nb2O5或La2O3的Ba(Ti0.9Sn0.1)O3基陶瓷的介电性能.结果表明掺入0.5%(摩尔比)Nb或La后Ba(Ti0.9Sn0.1)O3基陶瓷的居里温度向低温方向明显移动,而且介电常数显著增大,室温介电常数达30000,峰值介电常数达35000左右,同时介电损耗也明显增加.     

Dy掺杂BaTiO3陶瓷的制备及其介电性能

采用溶胶凝胶法制备了掺杂不同量Dy2O3(掺杂摩尔分数分别为0.001,0.002,0.003,0.005,0.007)的BaTiO3陶瓷,并对其介电性能的变化进行了研究.结果表明Dy2O3掺杂使BaTiO3陶瓷的电阻率明显降低,当添加量为0.005mol时,电阻率最小,为4.19×108Ω·m.Dy2O3掺杂使BaTiO3陶瓷的介电性能在不同掺杂量和不同频率下发生了明显变化,掺杂量为0.001mol、0.002mol时,BaTiO3陶瓷的介电特性和频率特性得到明显改善,在频率为1000Hz时介电性能相对较好.Dy2O3掺杂使BaTiO3陶瓷的介电温谱有所展宽,且Curie温度有所降低,交流电导随着温度的升高而增大,并在Curie点附近达到最高.     

Structure and piezoelectric properties of new (Bi0.5Na0.5)1?x?yBax(Yb0.5Na0.5)yTiO3 lead-free ceramics

New lead-free ceramics (Bi_0.5Na_0.5)_1−x−yBa_x(Yb_0.5Na_0.5)_yTiO₃ (x = 0.02–0.10 and y = 0–0.04) have been prepared by an ordinary sintering technique and their structure and piezoelectric properties have been studied. X-ray diffraction shows that Ba²⁺ and Yb³⁺ diffuse into the Bi_0.5Na_0.5TiO₃ lattices to form a solid solution with a pure perovskite structure and a morphotropic phase boundary (MPB) between rhombohedral and tetragonal phases is formed at 0.04 < x < 0.10. The partial substitutions of Ba²⁺ and Yb³⁺ for A-site ions of Bi_0.5Na_0.5TiO₃ decrease effectively the coercive field E _c and improve significantly the remanent polarization P _r. The ceramics with x = 0.06 and y = 0–0.02 situate within the MPB and possess the lower E _c and larger P _r, and thus exhibit optimum piezoelectric properties: d ₃₃ = 155–171 pC/N and k _p = 29.2–36.7%. The temperature dependences of the dielectric and ferroelectric properties suggest that the ceramics may contain both the polar and non-polar regions at temperatures near/above T _d.     

Nd掺杂的BaCeO3的阻抗谱和电性能研究

以固相反应法成功获得单一立方相的钙钛矿型化合物,ＢａＣｅ１－ｘＮｄｘＯ３－ａ。采用交流阻抗谱技术分别在空气,氧气和氩气以及不同水蒸气分压的湿空气中,于３００－７５０℃范围内研究Ｎｄ掺杂的ＢａＣｅＯ３样品的电学性质。     

Pb(Fe2/3W1/3)O3的制备及其介电性能研究

本文采用半化学法,即硝酸铁代替传统氧化物混合法中的三氧化二铁与PbO和WO3浆料混合,经850℃,2h预烧,一步合成了钙钛矿单相的Pb(Fe2/3W1/3)O3(PFW)预烧粉体;再经870℃和2h烧结,得到了纯钙钛矿相的PFW陶瓷,其理论密度大于98%,在1kHz时的最大介电常数εmax为8000,高于二次合成法和传统氧化物法制备的PFW陶瓷,表明半化学法对制备PFW陶瓷是可行的.     

SrCO3掺杂对PMN-PMnN-PZT-Ce压电陶瓷储能及介电弛豫性能的影响

通过铌铁矿先驱法制备了Pb(Mg_(1/3)Nb_(2/3))O_3-Pb(Mn_(1/3)Nb_(2/3))O_3-PbZrO_3-PbTiO_3+0.3%CeO_2(质量分数)+xSrCO_3(PMN-PMnN-PZT-Ce-xSr,x=0.00,0.03,0.05,0.07)四元系压电陶瓷,研究了SrCO_3含量的变化对Pb(Mg_(1/3)Nb_(2/3))O_3-Pb(Mn_(1/3)-Nb_(2/3))O_3-PbZrO_3-PbTiO_3+0.3%CeO_2(质量分数)(PMN-PMnN-PZT-Ce)压电陶瓷相结构、储能密度以及弛豫行为的影响。通过XRD表明,样品为单一稳定的钙钛矿结构,并且存在准同晶界(MPB);当x=0.07时,在外加电场60kV/cm下取得较好的储能性能:储能密度W1=0.31J/cm~3,储能效率η=0.47;通过修正Curie-Weise定律,较好地描述了陶瓷弥散相变的特征,弥散相变系数γ随着Sr~(2+)掺杂量的增加而增加。当x=0.07时,γ取得最大值1.972 8,此时弛豫现象最明显。     

氧化锆掺杂BaTiO_3陶瓷显微结构和介电性能研究

为了改变纯钛酸钡陶瓷的介电性能,以钛酸钡和氧化锆为原料,通过固相烧结法制备了不同物质的量比氧化锆掺杂钛酸钡基介电陶瓷。利用X射线衍射仪、透反射偏光显微镜和安捷伦LCR仪分析了其显微组成、相结构和介电特性。实验表明:氧化锆的掺杂不改变钛酸钡的晶体结构,当频率保持不变时,改变氧化锆在BaTiO3陶瓷中的掺杂量不会影响介电峰的位置,只影响了峰值大小。当掺杂物质的量比保持不变时,改变频率对峰的位置影响较大,呈现出随着频率的增加向高温区移动,峰值由大到小再到大的现象。在100 Hz下,当掺杂物质的量比为1.08∶100时介电常数最大。     

Sb2O3掺杂BNT-BZT1陶瓷的介电和铁电性能

采用固相反应法,制备了[0.9(Bi0.5Na0.5)TiO3-0.1Ba(Ti0.95Zr0.05)O3]+xwt%Sb2O3无铅压电陶瓷,研究了Sb2O3掺杂对样品相结构、介电、铁电性能的影响。实验结果表明:所有样品都形成了纯的钙钛矿结构,无第二相生成。材料存在明显的弛豫现象,从而改善了介电高温温度稳定性(在x=0.6wt%组分、1kHz下、150℃~250℃范围内,介电常数保持在4000左右),但结果同时也表明掺杂使铁电稳定性降低。