丝网印刷B-Li玻璃掺杂Ba0.5Sr0.5TiO3厚膜介电性能研究

钛酸锶钡(BST)陶瓷材料在外置偏压直流电场作用下,具有高的介电可调性,可以广泛地应用于电可调陶瓷电容器以及无源可调微波器件的设计与开发.通过B-Li玻璃的有效掺杂,实现BST陶瓷材料与Ag、Cu贱金属电极材料的低温友好烧结,是发展混合集成厚膜电路的技术要求.主要采用丝网印刷工艺,在Al2O3陶瓷衬底上,制备了B-Li玻璃掺杂的Ba0.5Sr0.5TiO3厚膜材料,并对其最佳烧结温度、物相结构、显微形貌以及介电性能进行了研究.结果表明,B-Li玻璃掺杂的Ba0.5Sr0.5TiO3厚膜材料在950℃可以实现低温烧结,得到了厚度为20μm的均匀致密厚膜材料;相比于BST陶瓷块体材料,5%(质量分数)B-Li玻璃掺杂BST厚膜的居里峰发生了明显的弥散和宽化,介电常数显著降低;在室温和10kHz频率下,其介电常数为210,介电损耗为0.0037,介电可调性可达15%以上,可以适用于厚膜混合集成电路与可调器件的设计和开发.     

锆钛酸钡陶瓷的介电性能研究

采用溶胶．凝胶法制备了掺锆钛酸钡（Ba（Zr0.2Ti0.8）03，简称BZT20）介电陶瓷。通过SEM电镜观察其表面形貌，X射线衍射（XRD）分析其相结构，阻抗分析仪测量BZT陶瓷的介电温谱。结果发现，通过掺锆（Zr含量为20％（摩尔分数）），SEM电镜照片表明制备的BZT20陶瓷粒径约60gm，XRD结果说明掺锆钛酸钡BZT20陶瓷是单一的钙钛矿结构，室温下为三方相结构。锆钛酸钡介电常数温谱没有明显的频率弥散，提高测试频率，温谱的峰值未发生漂移。     

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。     

非制冷红外探测器夹层厚膜工艺及介电性能研究

以钡、锶和锰醋酸盐为原料,采用新型溶胶-凝胶法制备锰掺杂4%mol、Ba/Sr分别为60/40、65/35和70/30的纳米粉体,均匀分散于组分相同的BST溶胶中,形成稳定的厚膜先体凝胶.浓度0.4mol/L钛酸钡凝胶薄膜种子层,作为不同组分厚膜之间的中间夹层.利用旋转涂覆工艺在LNO/Pt/Ti/SiO2/Si复合底电极上,制备出厚度约为6～10μm的BST介电增强型夹层厚膜.XRD测试结果表明,650℃热处理2h后的夹层厚膜为单一钙钛矿相,750℃热处理后2h的夹层厚膜在室温、环境温度25℃、频率1kHz下相对介电常数εγ和介质损耗tanδ分别约为1200和0.03,室温25℃附近较宽范围介温变化率>1.2%/℃,BST夹层厚膜无裂纹出现,表面平整,致密,是制备大阵列非制冷红外焦平面阵列(UFPA)的优选材料.     

聚酰亚胺多孔膜的制备与介电性能研究

以均苯四甲酸二酐和4,4′-二氨基二苯醚为原料合成聚酰亚胺前体聚酰胺酸溶液,通过溶液诱导相分离和热酰亚胺化法制备聚酰亚胺多孔膜。结果表明,用该方法得到的聚酰亚胺多孔膜具有较好的热稳定性。SEM分析显示,在不同的凝胶浴组成、凝胶浴温度和挥发时间等制膜条件下,可得到不同孔结构的多孔膜。与指状孔膜相比,海绵状孔多孔膜具有较低的介电常数。当凝胶浴组成DMAc/H2O为20/80、凝固浴温度为25℃、挥发时间为20min时,多孔膜断面几乎完全由海绵状孔组成,介电常数为1.45。     

La替代对Bi2O3-ZnO-Nb2O5陶瓷介电性能的影响

研究了A位La^3＋替代对Bi2O3-ZnO-Nb2O5（BZN）陶瓷结构和介电性能的影响。当La替代量X〈0．5时,陶瓷相结构为单一的立方焦绿石相。随着La替代量的增加,陶瓷样品的晶粒尺寸和密度逐渐减小。低温下的介电弛豫现象随着La替代量的增加也发生有规律的变化,介电常数逐渐减小,弛豫峰峰形逐渐宽化,峰值温度向低温方向移动。与La替代量为0．1、0．15、0．3和0．5相对应的弛豫峰的峰值温度分别为-95℃、-99℃、-109℃和-112℃。     

Ba4(Nd0.85Bi0.15)28/3Ti18O54陶瓷低温化研究

采用复合添加BaCuO2-CuO和BaO-B2O3-SiO2助剂的方法,研究了Ba4(Nd0.85Bi0.15)28/3 Ti18O54陶瓷的低温烧结特性和微波介电性能.添加2.5wt?CuO2-CuO和5wt?O-B2O3-SiO2后Ba4(Nd0.85 Bi0.15)28/3 Ti18O54陶瓷在950℃烧结成瓷,气孔率为5.29%,介电常数ε为60.25,Q·f值为2577GHz(5.6GHz),频率温度系数τf为 25.1ppm/℃,可与Cu电极浆料低温共烧.     

PMN铁电陶瓷B位有序与介电弛豫特性研究

本文采用退火热处理及掺入La³⁺离子两种方法,利用高分辨透射电镜、选区电子衍射、X射线衍射等技术对B位离子有序结构与介电弛豫性能的关系进行分析．研究表明,B位离子有序化是直接提高弥散相变（DPT）程度的原因,其机理是离子扩散,存在扩散平衡．退火仅能提高有序度,无法改变有序区尺寸;通过La³⁺离子掺杂,可有效提高有序区域大小,由于是非化学计量比,造成Nb⁵⁺离子在无序区中过度富集,形成焦绿石相．     

Sintering temperature-induced electrical properties of (Ba0.90Ca0.10)(Ti0.85Zr0.15)O3 lead-free ceramics

Effects of the sintering temperature on the microstructure and electrical properties of (Ba_0.90Ca_0.10)(Ti_0.85Zr_0.15)O₃ (BCTZ) lead-free piezoelectric ceramics have been studied, where these ceramics were prepared by the conventional oxide-mixed method at varied sintering temperatures from 1300 °C to 1500 °C. These BCTZ ceramics exhibits a phase transition from a rhombohedral phase to the coexistence of rhombohedral and tetragonal phases with an increase of sintering temperature. With an increase of sintering temperature, their relative density and average grain size gradually increase, and electrical properties are improved greatly. These BCTZ ceramics sintered at ～1440 °C have optimum electrical properties: d₃₃ ～ 442 pC/N and k_p ～ 48.9%, making it a promising material for lead-free piezoelectric ceramics.     

制备工艺对(Ba0.85Ca0.15)(Ti0.9Zr0.1)O3无铅压电陶瓷结构与性能的影响

采用液相混合与固相烧结相结合的方法制备了(Ba_0.85Ca_0.15)(Ti_0.9Zr_0.1)O₃ (BCTZ) 无铅压电陶瓷, 系统研究了烧结保温时间对其相结构、介电、压电和铁电性能的影响以及电学性能随温度的变化。研究结果表明: 制备的陶瓷样品具有单一的四方钙钛矿结构。当烧结温度为1540℃时, 随着保温时间的延长, 样品晶粒尺寸变大, 居里温度(T_c)升高, 压电性能提高, 电致伸缩性能下降。当保温时间为24 h时, BCTZ陶瓷综合性能最为优异: T_c ~90℃, tanδ < 0.05, k_p ~ 0.46, d₃₃ ~ 540 pC/N, P_s ~17 μC/cm²。陶瓷电学性能随温度变化测试结果又表明, BCTZ陶瓷的电学性能具有很强的温度依赖性, 随着温度的升高其电学性能逐渐下降。     

(Ba0.85Ca0.15)(Ti0.9Zr0.1-xSnx)O3无铅压电陶瓷的相结构与压电性能

钙锆共掺钛酸钡陶瓷(BCZT)具有优异的介电性能和压电性能, 是一类具有发展潜力的无铅压电陶瓷, 但其压电性能仍无法与铅基陶瓷媲美。为提高压电性能, 本研究对陶瓷材料进行Sn元素掺杂改性((Ba_0.85Ca_0.15)- (Ti_0.9Zr_0.1-xSn_x)O₃, x=0.02~0.07))。晶体结构分析证实所有组分的陶瓷无杂相, 处于正交相与四方相两相共存状态, 并具有较大的c/a; 显微结构分析发现所有陶瓷都很致密, 且平均晶粒尺寸随着Sn含量的增加而增大。当x=0.04时, 陶瓷最致密, 且室温处于准同型相界附近, 因此拥有最佳的电学性能: d₃₃=590 pC•N ^-1, k_p=52.2%, tanδ=0.016, ε ^T₃₃=5372, d ^*₃₃=734 pm•V ^-1, IR=57.8 GΩ•cm。本研究表明: Sn掺杂的BCZT基无铅压电陶瓷具有优异的压电性能, 有望在换能器、机电传感器和驱动器等方面得到应用。     

掺钇(Ba,Ca)(Ti,Zr)O_3电容器陶瓷抗还原性的研究

对掺钇的(Ba,Ca)(Ti,Zr)O3(BCTZ)电容器陶瓷进行了抗还原性研究,研究了不同摩尔分数的钇的掺杂对BCTZ电容器陶瓷的介电性能、显微结构和密度的影响。结果表明,随着Y2O3掺杂量的增加,BCTZ陶瓷的室温介电常数、介质损耗逐渐减小,居里温度向低温方向移动,同时绝缘电阻率升高,BCTZ陶瓷抗还原性能提高;Y2O3的掺入能够促进BCTZ陶瓷的致密化,并有利于抑制BCTZ陶瓷的晶粒生长。     

Structural and Dielectric Properties of Dy-doped( Ba, Sr, Ca) TiO3 Thick Films

Preparation and electrecatalytic activities of Pt-TiO2 nanotubes （Bao.57Sr0.33 Cao.10 ）TiO3 powders, prepared by the sol-gel method, were doped MnCO3 as acceptor and Dy2O3 as donor. This powder was mixed with an organic vehicle and BSCT thick films were fabricated by the screen-printing techniques on alumina substrate. The structural and dielectric properties of BSCT thick films were investigated with variation of Dy2O3 amount. As a result of the differential thermal analysis （DTA）, exothermic peak was observed at around 670℃ due to the formation of the polycrystalline perovskite phase. All the BSCT thick films showed the XRD patterns of a typical polycrystalline perovskite structure. The average grain size of BSCT thick films decreased with increasing amount of Dy2O3 . The relative dielectric constant and dielectric loss of the BSCT thick film doped Dy2O3 0.1mol% were 4637.4 and 1.6% at lkHz, respectively.     

Improved energy storage and electrocaloric properties of lead-free Ba0.85Ca0.15Zr0.1Ti0.9O3 ceramic

Lead-free Ba_0.85Ca_0.15Zr_0.1Ti_0.9O₃ (BCZT) ceramic powders were synthesized using the sol–gel method. The ceramics thickness was reduced to achieve high-energy storage and large electrocaloric effect in bulk ceramics. Dielectric, ferroelectric, energy storage, and electrocaloric properties were investigated for BCZT ceramic with 400 µm. Here, pure crystalline structure and homogenous microstructure were identified by XRD analysis and SEM measurements, respectively. The dielectric measurements revealed a maximum dielectric constant associated with ferroelectric–paraelectric phase transition. The maximum of \(\varepsilon^{\prime}_{{\text{r}}}\) was 17841, around 352 K. Furthermore, the BCZT ceramic exhibited improved energy storage and electrocaloric properties. A high recoverable energy density W_rec of 0.24 J/cm³ and a total energy density W_total of 0.27 J/cm³ with an efficiency coefficient of?~?88% at 423 K under an electric field of 55 kV/cm were obtained. Besides, The maximum value of ΔT?=?2.32 K, the electrocaloric responsivity ζ?=?0.42 K mm/kV, the refrigeration capacity RC?=?4.59 J/kg and the coefficient of performance COP?=?12.38 were achieved around 384 K under 55 kV/cm. The total energy density W_total and the temperature change ΔT were also calculated by exploiting the Landau–Ginzburg–Devonshire (LGD) theory. The theoretical results matched the experimental findings. These results suggest that the synthesized BCZT ceramic with reduced thickness could be a promising candidate for energy storage and electrocaloric applications.

     

Orientation-dependent phase transition and dielectric properties of Ba0.85Ca0.15Ti0.9Zr0.1O3 thin films

Polycrystalline Ba_0.85Ca_0.15Ti_0.9Zr_0.1O₃ (BCZT) thin films with (100) preferential and random orientation are prepared on the LaNiO₃ electrodes coated on Si substrates by chemical solution deposition process. The results show that the two types of films stabilize in the pure perovskite structure. The ferro-paraelectric phase transitions of two types of films occur at the temperature ranges of 280.2–297.8 K and 278.4–287.6 K, respectively. The dielectric constant, relaxation time and tunability of the random orientation film are smaller than those of the (100) preferential film but both almost have the similar leakage current characteristics. The mechanism associated with the change of the electrical properties of the thin films is also discussed.     

Low temperature sintering and properties of lead-free (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 ceramics with Ba(Cu0.5W0.5)O3 addition

The low-temperature sintering behavior of (Ba_0.85Ca_0.15)(Zr_0.10Ti_0.90)O₃ (BCZT) piezoelectric ceramics with Ba(Cu_0.5W_0.5)O₃ (BCW) addition has been investigated. The addition of 0.1 wt% BCW promotes the sinterability of BCZT ceramics owing to the generation of a liquid phase, resulting in a reduction of sintering temperature from 1,540 to 1,350 °C. The piezoelectric coefficient (d ₃₃), and the electromechanical coupling factor (kp) of the BCZT ? 0.1 wt%BCW specimen sintered at 1,350 °C were 555 pC/N and 55 %, respectively, while Curie temperature (Tc) increases from 85 to 95 °C.     

Dielectric,ferroelectric, and piezoelectric properties of Sb2O3-modified (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 lead-free ceramics

The microstructures, phase structure, and electrical properties have been investigated for the Sb₂O₃-modified (Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃ lead-free piezoelectric ceramics. The grain size was strongly affected by Sb₂O₃, and the solid solutions show a single phase perovskite structure. The ceramics with x = 0.1 % exhibit enhanced electrical properties of d ₃₃ ～556 pC/N, k _p ～52 %, ε _r ～3,895, tan δ ～1.3 %, and P _r ～12.6 μC/cm² when sintered at a low temperature of ～1,350 °C. The high temperature stability of ferroelectric properties (P _r ～14.8 μC/cm²) was obtained in the temperature range from ?60 to 0 °C. And with the addition of small amount of Sb₂O₃, Curie temperature (T _c ) maintains virtually unaltered.