溶胶-凝胶法制备的高压电常数(Bi_(0.5)Na_(0.5))_(1-x)Ba_xTiO_3系无铅压电陶瓷

测量了使用溶胶 凝胶工艺制备的 (Bi0 5Na0 5) 1 -xBaxTiO3(x =0 0 0 ,0 0 4 ,0 0 6 ,0 0 8,0 12 )系陶瓷的介电、压电、铁电和热释电性能 .由于使用了溶胶 凝胶工艺制备的粉料 ,因此所有样品的压电性能都得到了较大提高 .其中(Bi0 5Na0 5) 0 94 Ba0 0 6 TiO3系陶瓷具有该系列最大的压电常数 ,d33=173× 10 - 1 2 C N ,与传统工艺相比 ,d33提高了近4 0 % .同时 ,在一定范围内 ,随Ba含量的增加 ,材料的剩余极化Pr 和矫顽场Ec 逐渐减小 ,退极化温度逐渐降低 .对于 (Bi0 5Na0 5) 0 94 Ba0 0 6 TiO3系陶瓷 ,剩余极化和矫顽场分别为 2 5 μC cm2 和 2 8kV cm ,退极化温度约为 80℃ .     

溶胶-凝胶法制备Bi0.5Na0.5TiO3陶瓷及其电学特性

用溶胶-凝胶工艺成功制备出Bi05Na05TiO3纳米微粉，并利用此微粉烧结出高致密度的Bi05Na05TiO3陶瓷.这种新工艺制备的Bi05Na05TiO3陶瓷，其压电性能远远高于普通方法制备的陶瓷，其中压电常数d33和机电耦合系数kt分别高达102×10-12C/N和58%.同时发现，对于这种Bi05Na05TiO3陶瓷，室温时只需施加100kV/cm左右的交变电场，就可得到矩形度极好的饱和回线，得到的剩余极化Pr和矫顽场Ec分别为32μC/cm2和61kV/cm.而在100℃以上只需施加35kV/cm的极化电场就可使样品充分极化.     

铋层化合物Sr1+xBi4-xTi4-xTaxO15(x=0—1)陶瓷的介电和铁电特性

研究了铋层化合物Sr1+xBi4-xTi4-xTaxO15(x=0—1)陶瓷的介电和铁电特性.研究发现随着x值的增大,材料的居里点由540℃降到30℃左右,但材料始终具有铁电性.对于SrBi4Ti4O15陶瓷施加120kVcm的电场仍无法得到饱和的回线,此时的剩余极化和矫顽场分别约为7μCcm2和73kVcm.对于x=04—05的材料由于它们同时具有较高的居里温度300℃—360℃,较大的剩余极化7—8μCcm2和较小的矫顽场37—47kVcm,因此是一类性能较为优良的铁电材料. 关键词： 居里温度 剩余极化 矫顽场     

椭偏光谱法研究溶胶-凝胶TiO2薄膜的光学常数

以钛酸丁酯为前驱体,采用溶胶-凝胶工艺成功制备了TiO₂薄膜.利用反射式椭圆偏振光谱仪测量了薄膜的椭偏参量Ψ和Δ,并用Cauchy模型对椭偏参数进行数据拟合,得到了薄膜的厚度和光学常数在380—800 nm的色散关系.用分光光度计测量了薄膜的反射率,并用干涉法计算薄膜的厚度;使用原子力显微镜观测了薄膜的表面微结构,分析讨论了不同退火温度处理的薄膜微结构与光学常数之间的关系.研究结果表明,Cauchy模型能较好地符合溶胶-凝胶TiO₂薄 关键词： 光学常数 2薄膜')" href="#">TiO₂薄膜 溶胶-凝胶 椭圆偏振     

溶胶-凝胶法制备氧化锌薄膜的压电行为

"采用溶胶-凝胶技术在单晶硅Si(111)上制备了ZnO压电薄膜,并以扫描电镜、X射线衍射仪(XRD)和原子力显微镜(AFM)进行了表征．XRD衍射实验表明ZnO薄膜随着膜厚的增大,其(002)取向逐渐增强;AFM研究了薄膜的表面形貌、粗糙度与晶粒大小的结果表明,ZnO压电薄膜的粗糙度与晶粒寸随着薄膜厚度的增大而减小．粗糙度为2.188~0.914 nm．利用PFM研究压电系数,发现随着薄膜厚度的增加,(002)生长方向增强,压电系数逐渐增大;当力参数小于薄膜的表面粗糙度时,压电系数测量不准确且在较大幅度     

溶胶-凝胶法制备纳米多孔SiO2薄膜

以正硅酸乙酯(TEOS)为原料，采用旋转涂敷的方法，结合溶胶-凝胶技术在硅衬底上制备超低介电常数多孔SiO₂薄膜.采用两种不同的改性方法对薄膜表面进行改性，傅里 叶变换红外光谱分析发现改性后薄膜中含有大量的—CH₃键，从而减少了孔洞塌陷.用扫 描电子显微镜观察薄膜的表面形貌，发现薄膜内孔洞尺寸在70—80 nm之间.调节溶胶pH值，发现pH值越小凝胶时间越长.对改性样品热处理的结果表明，在300 ℃时介电常数最低达2.05. 关键词： 2')" href="#">多孔SiO₂ 低介电常数 溶胶-凝胶     

溶胶-凝胶法制备的GeO2-SiO2凝胶玻璃的红光发射

以3三氯锗丙酸和正硅酸乙酯为原料采用溶胶凝胶法制备了GeO2SiO2凝胶玻璃.室温下以532nm激光(Nd:YAG)激发GeO2SiO2凝胶玻璃有一强的发光峰,这种发光有两个发光带,其峰位分别在575nm和624nm.该发光现象是由镶嵌在GeO2SiO2凝胶玻璃中GeO2纳米颗粒产生的.利用吸收光谱和TEM对GeO2SiO2凝胶玻璃进行了表征,结果发现随着Ge含量的增加凝胶玻璃中GeO2纳米颗粒的尺寸越来越大,吸收边向低能边移动.X射线衍射和电子衍射确定GeO2SiO2凝胶玻璃中GeO2颗粒的结构为非晶结 关键词： GeO2-SiO2凝胶玻璃 溶胶-凝胶法 红光发射     

溶胶-凝胶法制备高折射率TiO2薄膜

采用溶胶- 凝胶法制备了TiO2纳米晶溶胶,并以旋涂法（spin-coating）镀制了高折射率光学薄膜。借助光散射技术和透射电镜研究了溶胶的微结构。采用原子力显微镜、场发射扫描电镜、紫外-可见-近红外光谱仪、椭偏仪、漫反射吸收光谱及强激光辐照实验,对膜层的结构、光学性能及抗激光损伤性能进行了系统的表征。结果显示:纳米晶薄膜的折射率达到了1.9,而传统的溶胶-凝胶薄膜折射率只有1.6;同时纳米晶薄膜的抗激光损伤阈值与传统的溶胶-凝胶薄膜相差不大,在1 064 nm处分别为16.3 J/cm2(3 ns脉冲) 和16.6 J/cm2(3 ns脉冲);纳米晶溶胶薄膜可以在保持较高抗激光损伤阈值情况下,大幅度提高薄膜折射率。     

溶胶-凝胶法制备BaTiO3/SrTiO3多层膜的介电增强效应

采用溶胶凝胶法,在PtTiSiO2Si衬底上逐层制备了BaTiO3SrTiO3多层膜.从多层膜的XRD图可看出明显的双峰,分别对应为BaTiO3和SrTiO3的特征峰,表明样品已形成了多层膜结构.与同厚度的Ba05Sr05TiO3单层膜比较,BaTiO3SrTiO3多层膜的介电系数得到了明显的增强,在频率为10kHz时,周期为66nm的BaTiO3SrTiO3多层膜相对于同厚度的Ba05Sr05TiO3薄膜的介电系数从245增强到595,而损耗依然保持较低,分别为0029和0033.研究同时表明,BaTi 关键词： 溶胶-凝胶法 多层膜 介电增强     

A位等价与非等价取代对(K0.5Na0.5)NbO3陶瓷极化的影响

研究了在铌酸钾钠基陶瓷中,A位等价与非等价取代对陶瓷极化温度和极化电场的影响,结果表明:A位等价取代的陶瓷对极化温度和极化电场没有强烈依赖性,可以使极化足够充分,能有效提高铌酸钾钠基陶瓷的压电性能;相反,A位非等价取代的陶瓷对极化温度和极化电场敏感,容易击穿,极化不充分,限制了铌酸钾钠基陶瓷的压电性能. 关键词： 铌酸钾钠 极化 压电     

Na0.25K0.25Bi0.5TiO3无铅压电陶瓷的介电特性研究

用固相反应法制备了Na0.25K0.25Bi0.5TiO3(NKBT50)陶瓷,研究了该陶瓷在室温至400℃温度范围内的介电性能.发现该陶瓷的介电温谱与烧结气氛、极化状态有关.在空气中烧结的未极化样品在70℃附近存在介电和损耗峰,而极化后及在氧气氛中烧结的样品并不存在该介电、损耗峰.分析认为70℃的介电和损耗峰与氧空位形成的缺陷偶极子的极化弛豫有关.热激电流显示,陶瓷的去极化温度为225℃,与此相对应的介电、损耗峰也与氧空位有关.     

Enhanced piezoelectric properties near the morphotropic phase boundary in lead-free (1-x)(Bi0.5K0.5)TiO3-xBi(Ni0.5Ti0.5)O3 ceramics

Lead-free piezoelectric ceramics of the composition (1-x)(Bi_0.5K_0.50)TiO₃-xBi(Ni_0.50Ti_0.50)O₃ or (1-x)BKT-xBNiT (when x = 0–0.20 mol fraction) were prepared by a conventional mixed-oxide method and sintered at 1050 °C for 4 h. The effects of BNiT content on the phase equilibria, and the dielectric, ferroelectric and piezoelectric properties were systematically investigated. High density sintered specimens (5.71–6.12 g/cm³) were obtained for all compositions. X-ray diffraction patterns showed that all BKT-BNiT samples exhibited a single perovskite phase which confirms that BNiT and BKT formed a solid solution up to x = 0.20. A morphotropic phase boundary (MPB) separating a BKT-rich tetragonal phase and a BNiT pseudo-cubic phase was identified over the compositional range 0.05 < x < 0.10, where enhanced electrical properties were observed. The optimum dielectric properties (ε_r = 1710, tanδ = 0.036), ferroelectric properties (P_r = 16.6 μC/cm², E_c = 22.5 kV/cm and R_sq = 0.86) and piezoelectric properties (d₃₃ = 288 pC/N, S_max = 0.22% and d^*₃₃ = 313 pm/V) were observed with a relatively high T_m ∼ 304 °C within this MPB region. Overall, these results indicate that the BKT-BNiT ceramic system is a promising lead-free piezoelectric candidate for further development for actuator applications.     

Transverse piezoelectric properties of Mn-doped Bi0.5Na0.5TiO3 thin films

Lead-free (Bi_0.5Na_0.5)(Ti_1-xMn_x)O₃ (BNTMn-x; x = 0, 0.0025, 0.0050, 0.0100) thin films were fabricated using a chemical solution deposition method on Pt/TiO₂/SiO₂/Si substrate. The effect of Mn substitution on crystal structures, surface morphologies, and ferroelectric and transverse piezoelectric properties of BNTMn-x thin films was investigated. The 0.5 mol% Mn-doped (Bi_0.5Na_0.5)(Ti_0.995Mn_0.005)O₃ thin film exhibited a well-saturated ferroelectric P-E hysteresis loop at room temperature. A remnant polarization (P_r) of 16 μC/cm² was obtained for the BNTMn-0.0050 film at an applied electric field of 400 kV/cm. In addition, a 1.12-μm-thick BNTMn-0.0050 film was applied as a cantilever. The Pt/BNTMn-0.0050/Pt/TiO₂/SiO₂/Si unimorph cantilever exhibited a high transverse piezoelectric coefficient ($e_{31}^1$) of 2.43 C/m².     

Synthesis and physical properties of Ca- and Ta-modified (K,Na)NbO3 lead-free piezoelectric ceramics

Polycrystalline samples of lead-free Ca and Ta co-substituted potassium sodium niobate (K_0.5Na_0.5NbO_3, KNN) ceramics have been prepared by solid state reaction technique. X-ray diffraction showed formation of a single-phase perovskite structure with orthorhombic symmetry. Substitution inhibits the grain growth, improves densification and decreases the ferro-paraelectric phase transition temperature. Temperature dependent dielectric permittivity studies demonstrate significant decrease in peak-permittivity values in the substituted samples. Bulk longitudinal piezoelectric coefficient is significantly enhanced, up to ～155 pC/N for (K_0.48Na_0.48Ca_0.02)(Nb_0.85Ta_0.15O₃) as compared to 95 pC/N for pristine KNN ceramic. Local piezoelectric properties have been observed by piezoresponse force microscopy (PFM) technique. Distinct piezocontrast was studied in both vertical and in-plane modes of PFM for all samples. The samples exhibit self-polarization effect in the unpoled state and effective local vertical piezoelectric coefficient was the largest in Ca and Ta co-substituted sample whereas the in-plane piezoelectric coefficient was maximum for Ca-substituted KNN sample. These studies are important for using substituted lead free KNN materials in various piezoelectric applications.     

The effect of CuO and NiO doping on dielectric and ferroelectric properties of Na0.5Bi0.5TiO3 lead-free ceramics

In the present work, lead-free piezoelectric ceramics (Na_0.5Bi_0.5)TiO₃ –xCuO–yNiO (for x = 0.0, 0.02, 0.04 and 0.06) have been prepared by a conventional solid-state reaction method. An investigation of CuO and NiO doping in bismuth sodium titanate (BNT) and a study of the structure, morphology, and dielectric and ferroelectric properties of the NBT–CuNi system have been conducted. Phase and microstructural analysis of the (Na_0.5Bi_0.5)TiO₃ (NBT) based ceramics has been carried out using X-ray diffraction and scanning electron microscopy (SEM) techniques. Field emission scanning electron microscopy (FE-SEM) images showed that inhibition of grain growth takes place with increasing Cu and Ni concentration. The results indicate that the co-doping of NiO and CuO is effective in improving the dielectric and ferroelectric properties of NBT ceramics. Temperature-dependent dielectric studies have also been carried out at room temperature to 400 °C at different frequencies. The NBT ceramics co-doped with x = 0.06 and y = 0.06 exhibited an excellent dielectric constant ?_r = 1514. The study suggests that there is enormous scope of application of such materials in the future for actuators, ultrasonic transducers and high-frequency piezoelectric devices.