溶胶-凝胶法制备CaBi_4Ti_4O_(15)基陶瓷粉体

采用溶胶凝-胶法制备V掺杂的铋层复合物CaBi4Ti3.95V0.05O15.025(CBTVO)陶瓷粉体,利用TDA/TG和IR光谱分析前驱体凝胶的变化,利用XRD和SEM分析和观察不同热处理温度下CBTVO粉体的相组成和颗粒形貌,利用EDX测定粉体颗粒的元素分布,并对CaBi4Ti4O15类钙钛矿主晶相的形成过程和机制进行探讨。结果表明:有机物在300℃之前基本上完全排除,铋层类钙钛矿结构的主晶相在500℃开始形成,并含有少量的Bi2O3相。Bi2Ti2O7相在590℃左右出现,当热处理温度高于800℃后则完全消失。热处理后的粉体颗粒呈片状,900℃热处理后粉体颗粒尺寸介于200～600nm之间,且各元素分布接近于化学计量比。     

铋层状化合物Sr0.3Ba0.7Bi4-xLaxTi4O15陶瓷材料的介电性能

采用固相烧结工艺制备了铋层状化合物Sr0．3Ba0.7Bi4-xLaxTi4O15铁电陶瓷。X射线衍射证实：La含量很大的范围内(x=0～1)均形成了层状钙钛矿结构固熔体。Sr0.3Ba0.7Bi3.25La0.75Ti4O15粉料在低温下难以烧结,随着烧结温度的提高,Sr0．3Ba0.7Bi4-xLaxTi4O15陶瓷密度增加的同时,产生焦绿石相,但La的加入在一定程度上抑制焦绿石相的形成．Sr0．3Ba0.7Bi4-xLaxTi4O15陶瓷的介电常数峰在10kHz时较宽,在100Hz时,介电常数峰被随温度升高而逐渐增大的介电常数所“屏蔽”,材料损耗角正切随温度升高而增大,在低频下增加得更快。     

Enhanced piezoelectric performance in Na0.5Bi4.5Ti4O15-based bismuth-layered ceramics by Nb/Mn doping modification

In this work, Na_0.5Bi_4.5Ti_3.94–xMn_0.06Nb_xO_15+y bismuth-layered ferroelectric ceramics were prepared by a solid-state reaction method. The effect of Nb⁵⁺ content on crystal morphology, electrical properties, and piezoelectric performance were systematically investigated. The results show that the introduction of Nb⁵⁺ into Na_0.5Bi_4.5Ti_3.94–xMn_0.06Nb_xO_15+y ceramics to replace Ti⁴⁺ increases the ratio of b/a lattice parameter, leading to the TiO₆ octahedral distortion and the structural transformation tendency from the orthorhombic to tetragonal phase, which facilitates dipole movements of Na_0.5Bi_4.5Ti_3.94–xMn_0.06Nb_xO_15+y ceramics. Therefore, the ferroelectric properties of Na_0.5Bi_4.5Ti_3.94–xMn_0.06Nb_xO_15+y ceramics are improved, and an enhanced piezoelectric coefficient of 30 pC/N combining great temperature stability with d₃₃ value higher than 25 pC/N in the temperature range of 25°C–450°C has been realized in Na_0.5Bi_4.5Ti_3.94–xMn_0.06Nb_xO_15+y ceramics with x = 0.08 mol. Our work provides a good model for designing lead-free ultrahigh Curie temperature piezoelectric devices that can be practically applied in extremely harsh environments.     

Nb5+掺杂改性CaBi4Ti4O15压电陶瓷的研究

采用传统固相烧结法,制备了CaBi4Ti(1-x)NbxO1(5x=0.00-0.05,CBT-N)系铋层状结构无铅压电陶瓷。研究了Nb5+掺杂对CBT压电陶瓷压电与介电性能的影响。研究结果表明:添加Nb5+离子,改善了CBT陶瓷的烧结特性,提高了瓷体的致密度。Nb2O5的引入降低了CBT系列陶瓷的介质损耗,改善了陶瓷的压电与介电性能。当掺入量x=0.04(CaBi4Ti0.96Nb0.04O15)时制备的CBT基铋层状压电陶瓷具有优异的压电性能:d33=14pC/N,Qm=3086,εr=212,tanδ=0.0041,kt/kp=1.681。     

铋层状化合物SrBi4-xCexTi4O15陶瓷的铁电性能研究

采用溶胶-凝胶法制备了SrBi4-xCexTi4O15(x=0.2~0.8)铁电陶瓷,X-射线衍射证实随着x掺杂量的增加,晶粒中a、b轴取向的晶粒逐渐增多,与扫描电镜的分析结果一致。介温谱表明样品的居里温度最大为590℃,通过研究铁电性发现,剩余极化和矫顽场先增大后减少,当x=0.6时它们分别达最大值为3.56μC/cm2和9.38 kV/cm,这是氧空位与晶格畸变共同作用的结果。     

Er3+ 掺杂对Bi3Ti1.5W0.5O9-Bi4Ti3O12 共生无铅压电陶瓷性能的影响

用传统固相法制备了Bi_7-x Er _x Ti_4.5W_0.5O₂₁(BTW-BIT-xEr³⁺,x=0.05、0.10、0.15、0.25、0.35)共生铋层结构无铅压电陶瓷,用BTW-BIT-xEr³⁺的XRD和SEM表征其相结构和形貌,研究了Er³⁺掺杂对其上转换发光性能和电学性能的影响。结果表明：在这种陶瓷中生成了铋层状结构的单一晶相。在980 nm光波激发下所有组分的上转换荧光谱中都能清晰地观察到两个绿光和一个红光发射峰,峰的中心分别位于532 nm、548 nm和660 nm处。改变掺杂Er³⁺离子浓度可调节其强度比。根据BTW-BIT-0.15Er³⁺样品在532 nm和548 nm绿光的光强比拟合了290~440 K的温度灵敏度,结果表明440 K处的灵敏度最大为0.0023 K^-1。Er³⁺离子替代BTW-BIT-xEr³⁺伪钙钛矿层的Bi³⁺使氧空位浓度的降低,降低了高温介电损耗,提高了激活能和压电常数。BTW-BIT-0.15Er³⁺陶瓷的综合电学性能最优,分别为d₃₃=14 pC/N、T_c=697℃,tanδ=0.53%、Q_m=2055。这种陶瓷材料具有最优的发光性能和良好的热稳定性。     

Thermal and piezoelectric properties of Bi3.15Nd0.85Ti3O12 thin film prepared by metal organic decomposition

Bi3.15Nd0.85Ti3O12(BNT) powder and thin film were prepared by metal organic decomposition(MOD) method.The heat flow curve of BNT powder was measured with a modulated temperature differential scanning calorimeter,and thermal physical parameters such as thermal conductivity coefficient and thermal diffusion coefficient were obtained from the heat flow curve.The phase identification,ferroelectric,and piezoelectric properties of BNT thin film annealed at 700°C were investigated with X-ray diffractometer,ferroelectric analyzer,and scanning probe microscope.The results show that the thin films consisting of a single phase of bismuth-layered perovskite are polycrystalline,without a preferred orientation.Remnant polarization 2Pr is 63.2μC/cm 2 under 530 kV/cm applied field,and the effective piezoelectric coefficient d33 is 30 pm/V.