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1.
沈彩  刘庆峰  刘茜 《无机材料学报》2004,19(6):1339-1344
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.  相似文献   

2.
水基溶胶-凝胶法制备Ba0.5Sr0.5TiO3薄膜及其介电性能研究   总被引:8,自引:0,他引:8  
本文研究了一种以水为溶剂的Ba0.5Sr0.5TiO3(BST)液体源溶液,并用Sol-Gel技术制备出BST薄膜,实验中,对水基BST液体源浓缩凝胶进行了DTA/TGA分析,XRD谱分析显示,BST膜呈现纯钙钛矿相结构.从SEM电镜照片可以看到,BST薄膜厚度均匀一致,650℃热处理20min后,晶粒大小为200nm左右.性能测试结果表明,介电性能与膜厚有关,厚度为1250的BST薄膜具有较优良的介电性能,当测试频率为1kHz时,介电常数为330,介电损耗为0.043左右.  相似文献   

3.
徐华  沈明荣  方亮  甘肇强 《功能材料》2004,35(5):603-605,609
采用脉冲激光沉积法,在Pt/Ti/SiO2/Si基底上分剐制备厚度为350nm的Ba0.5Sr0.5TiO3(BST)、Pb0.5Ba0.5TiO3(PBT)和Pb0.5Sr0.5TiO3(PST)薄膜并研究了它们的介电性质。XRD显示,在相同的制备条件下三者具有不同的择优取向,PST具有(110)择优取向,PBT具有(111)择优取向,而BST则是混合取向。SEM显示三者样品表面均匀致密,颗粒尺寸大约在50nm至150nm之间。PST与BST、PBT相比有更高的介电常数,在频率为10kHz时,分别为874、334和355,而损耗都较低,分别为0.0378、0.0316和0.0423,同时PST漏电流也是最小的。测量薄膜的C-V特性扣铁电性能表明室温下BST呈现的是顺电相,PST和PBT则呈铁电相。本文也测量了薄膜在不同频率下的介电温度特性,BST、PBT和PST均表现出频率弥散现象,即随着频率的降低.居里温度降低而介电常数会升高。并测得BST和PST的居里温度分剐为-75和150℃。而PBT的居里温度在250℃以上。本文研究表明:与BST相比较,PBT的介电常数与之相近,漏电流较大;而PST具有高介电常数,较小的漏电流和较大的电容-电压调谐度,在相关半导体器件中的应用将有很大的潜力。  相似文献   

4.
采用溶胶-凝胶工艺成功制备出K0.5Bi0.5TiO3微细粉料,并利用此微粉烧结出成瓷良好的K0.5Bi0.5TiO3陶瓷.用X射线衍射法测定了K0.5Bi0.5TiO3陶瓷粉末室温和高温(600℃)时的点阵常数,确定K0.5Bi0.5TiO3的高温相为立方结构(点群m3m)指标化其衍射线,给出了K0.5Bi0.5TiO3陶瓷粉末的多晶X射线衍射数据.以此X射线衍射方法研究了K0.5Bi0.5TiO3陶瓷粉末的铁电-顺电相变,测定了k0.5Bi0.5TiO3的介电特性.所作测量表明K0.5Bi0.5TiO3可能是一种有序-无序型弛豫铁电体,呈现一级弥散相变特征.这可采用极性微区理论阐释,弛豫特性是由此类材料非均衡性产生的极性微区在逐渐冻结过程中引起的.  相似文献   

5.
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.  相似文献   

6.
采用溶胶凝胶法制备了Sn0.5Ti0.5O2固溶体.用X射线衍射(XRD)和红外(IR)技术对材料的结构和热稳定性进行了分析表征.固溶体的热稳定性与起始反应温度有关,40℃水浴制备的凝胶经过1000℃烧结就发生了相分解,出现了富Sn、富Ti相,而80℃水浴制备的凝胶经过1200℃烧结也不发生相分解,仍以Sn0.5Ti0.5O2相存在.将胶体制成了薄膜元件并测试了元件的气敏性能,发现此元件对H2S气体有一定的灵敏度.  相似文献   

7.
采用新型的Sol-gel工艺制备了Ba0.6Sr0.4TiO3(BST)超细粉体,将BST粉体进行压制和烧结,获得了晶粒尺寸在1μm以内的BST陶瓷块体.观察了BST陶瓷块体的结晶情况并测定了其电学性能.在Sol-gel工艺中,加入了有机大分子量聚乙烯吡咯烷酮(polyvinyl pyrrolidone,PVP)制备BST前驱体.实验结果表明PVP的加入可有效增加前驱体的稳定性和分散性,降低BST陶瓷的预烧温度约250℃,并在1200℃获得晶粒细小、致密的BST陶瓷.BST陶瓷,显示弥散相变特征.  相似文献   

8.
以钛酸正丁酯为前驱体,乙酰丙酮为络合剂,分别在室温和70℃进行对前驱体改性的络合反应,获得改性前驱体Ti(O-Bu)4-x(AcAc)x.以异丙醇为溶剂,采用溶胶-凝胶(sol-gel)法制备0.1—3.0mol%Er^3+抖掺杂TiO2粉末.差热-热重(TG-DTA)分析结果表明,由室温络合改性前驱体制备的粉末,无定型到锐钛矿和锐钛矿到金红石的相变温度,较由70℃络合改性前驱体制备的粉末均升高40℃.X射线衍射(XRD)分析表明,700℃烧结,室温络合所得掺0.1-3.0mol%Er^3+:TiO2粉末为单一锐钛矿结构,70℃络合所得粉末为锐钛矿和少量金红石的混合相结构.400-800℃烧结,两种络合所得粉末均获得中心波长为1.53μm的多峰结构光致发光(PL)谱.其中,700℃烧结的粉末PL强度最强.70℃络合较室温络合的粉末PL强度可提高3倍.  相似文献   

9.
溶胶-沉淀法制备钛酸锶钡粉末及其水热处理   总被引:5,自引:0,他引:5  
通过溶胶一沉淀法制备出完全钙钛矿结构的Ba0.71Sr0.29TiO3(BST)粉末,粉末的颗粒尺寸约为300nm。但得到的BST粉末不稳定,在乙酸中容易兮解。通过TG-DTA和XRD分析,直接沉淀得到的粉末颗粒失重大,而且由于颗粒所吸附的有机物阻碍了Ba^2 和Sr^2 的扩散,造成了直接沉淀的BST颗粒内部的组分不均匀和结晶不完全。通过对直接沉淀的BST粉末进行150-200℃的水热后处理,其结晶性得到了很大的改善,稳定性也得到了提高。实验表明,水热处理具有与烧结相似的效果,但BST粉末的分散性得到了改善。  相似文献   

10.
为了满足微波器件小型化的需要,开发高介电常数的低温烧结微波介质材料成为一种趋势.采用复合掺杂低熔点氧化物来降低BaO-Sm2O3-TiO2系(BST)微波介质陶瓷的烧结温度,通过X射线衍射和扫描电子显微镜分析其物相组成和显微结构,用阻抗分析仪测量了陶瓷材料的介电性能.结果表明:在Ba4(Sm1-0.15Bi0.15)28/3Ti18O54的基质陶瓷材料中,复合掺杂3%的ZnO和2%的B2O3时,其烧结温度为1060℃,得到的BST微波介质陶瓷的介电性能为:εr≈64,tanδ≈1.2×10-3,τf=-8.3×10-5/℃.  相似文献   

11.
The (x) Ni0.5Cu0.5Fe2O4 + (1−x) Ba0.5Pb0.5Ti0.5Zr0.5O3 ME composites have been synthesized by a standard ceramic method. The presence of single phase in x = 0 and x = 1 as well as two phases in x = 0.15, 0.30 and 0.45 composites has been confirmed by XRD. The dielectric constant (ε′) and dielectric loss (tan δ) have been studied as a function of temperature and frequency. These composite materials exhibit maximum dielectric constant with a variation of frequency and temperature. The composite 15% Ni0.5Cu0.5Fe2O4 + 85% Ba0.5Pb0.5Ti0.5Zr0.5O3 had the highest magnetoelectric voltage coefficient of 0.248 mV/cm Oe at room temperature among the studied composites.  相似文献   

12.
CdTe0.5Se0.5/Cd0.5Zn0.5S core/shell quantum dots (QDs) with a tunable photoluminescence (PL) range from yellow to dark red (up to a PL peak wavelength of 683 nm) were fabricated using various reaction systems. The core/shell QDs created in the reaction solution of trioctylamine (TOA) and oleic acid (OA) at 300 °C exhibited narrow PL spectra and a related low PL efficiency (38%). In contrast, the core/shell QDs prepared in the solution of 1-octadecene (ODE) and hexadecylamine (HDA) at 200 °C revealed a high PL efficiency (70%) and broad PL spectra. This phenomenon is ascribed that the precursor of Cd, reaction temperature, solvents, and ligands affected the formation process of the shell. The slow growth rate of the shell in the solution of ODE and HDA made QDs with a high PL efficiency. Metal acetate salts without reaction with HDA led to the core/shell QDs with a broad size distribution.  相似文献   

13.
T. Yu  K.W. Kwok  H.L.W. Chan 《Materials Letters》2007,61(10):2117-2120
(1 − x)Bi0.5Na0.5TiO3-xBi0.5K0.5TiO3 [BNT-BKT-100x] thin films have been successfully deposited on Pt/Ti/SiO2/Si substrates by a sol-gel process together with rapid thermal annealing. A morphotropic phase boundary (MPB) between Bi0.5Na0.5TiO3 and Bi0.5K0.5TiO3 was determined around x ∼ 0.15. Near the MPB, the film exhibits the largest grain size, the highest ε value (360) and the largest Pr value (13.8 μC/cm2). The BNT-BKT thin film system is expected to be a new and promising candidate for lead-free piezoelectric applications.  相似文献   

14.
Lead-free piezoelectric ceramics (1 − x − y)Bi0.5Na0.5TiO3xBi0.5K0.5TiO3yBiCoO3 (x = 0.12–0.24, y = 0–0.04) have been fabricated by a conventional solid-state reaction method, and their structure and electrical properties have been investigated. The XRD analysis shows that samples with y ≤ 0.03 exhibit a pure perovskite phase and very weak impurity reflections can be detected in the sample with y = 0.04. With x increasing from 0.12 to 0.24 and y increasing from 0 to 0.04, the ceramics transform gradually from a rhombohedral phase to a tetragonal phase and rhombohedral–tetragonal phase coexistence to a pseudocubic phase, respectively. The morphotropic phase boundary (MPB) of the system between rhombohedral and tetragonal locates in the range of x = 0.18–0.21, y = 0–0.03. The ceramics near the composition of the MPB have good performances with piezoelectric constant d 33 = 156 pC/N and electromechanical coupling factor k p = 0.34 at x = 0.21 and y = 0.01, which attains a maximum value in this ternary system. Adding content of BiCoO3 leads to a disappearance of the response in the curves of dielectric constant-temperature to the ferroelectric–antiferroelectric transition. The temperature dependence of dielectric properties suggests that the ceramics are relaxor ferroelectrics. The results show that (1 − x − y)Bi0.5Na0.5TiO3xBi0.5K0.5TiO3yBiCoO3 ceramics are good candidate for use as lead-free ceramics.  相似文献   

15.
Lead-free piezoelectric ceramics (1 − x)Bi0.5(Na0.84K0.16)0.5TiO3xBa0.77Ca0.23TiO3 (BNKT–xBCT, x = 0–0.04) were synthesized by conventional solid-state reaction method. The piezoelectric, dielectric, and ferroelectric characteristics of the ceramics are investigated and discussed. The XRD results show that Ba0.77Ca0.23TiO3 (BCT) has diffused into Bi0.5(Na0.84K0.16)0.5TiO3 (BNKT) lattices to form a new solid solution. It is shown that moderate additive of BCT (x ≤ 0.025) in BNKT–xBCT ceramics can enhance their piezoelectric and ferroelectric properties. Three dielectric anomalies are observed in BNKT–xBCT (x ≤ 0.03) ceramics. The piezoelectric measurements and P–E hysteresis loops reveal that BNKT–0.025BCT ceramic has the highest piezoelectric performance and strongest ferroelectricity in all the samples. Piezoelectric constants d 33, k p, and k t of 175 pC/N, 29.1, and 54% are, respectively, achieved. Remnant polarization P r and coercive field E c reach 28.3 μC/cm2 and 24.2 kV/cm, respectively.  相似文献   

16.
Good oxidation resistance of hard coatings is important for cutting tools. Ti0.5Al0.5N coating and Ti0.5Al0.4Si0.1N coating were deposited by cathodic arc evaporation and their oxidation behavior at 850 °C, 900 °C and 1000 °C was compared. The effect of Si addition on the oxidation resistance of Ti0.5Al0.4Si0.1N was investigated. Results show that the oxidation resistance of Ti0.5Al0.4Si0.1N coating at 850-1000 °C is superior to Ti0.5Al0.5N coating. The improved oxidation resistance of Ti0.5Al0.4Si0.1N coating can be ascribed to the combined action of Al2O3 and SiO2 barrier layer, the reduction of columnar structure and the refinement of grains. In particular, Si addition increases the diffusion coefficient of Al and promotes the preferential formation of Al2O3 barrier layer.  相似文献   

17.
Lead-free piezoelectric ceramics with compositions around the morphotropic phase boundary (MPB) x(Na0.5Bi0.5)TiO 3-y(K0.5Bi0.5)TiO3-zBaTiO 3 [x + y + z = 1; y:z = 2:1] were synthesized using conventional, solid-state processing. Dielectric maximum temperatures of 280degC and 262degC were found for tetragonal 0.79(Na0.5Bi0.5)TiO3-0.14(K0.5 Bi0.5)TiO3-0.07BaTiO$ d3 (BNBK79) and MPB composition 0.88(Na0.5Bi0.5)TiO3-0.08(K 0.5Bi0.5)TiO3-0.04BaTiO$ d3 (BNBK88), with depolarization temperatures of 224degC and 162degC, respectively. Piezoelectric coefficients d33 were found to be 135 pC/N and 170 pC/N for BNBK79 and BNBK88, and the piezoelectric d31 was determined to be -37 pC/N and -51 pC/N, demonstrating strong anisotropy. Coercive field values were found to be 37 kV/cm and 29 kV/cm for BNBK79 and BNBK88, respectively. The remanent polarization of BNBK88 (~40 muC/cm2) was larger than that of BNBK79 (~29 muC/cm2). The piezoelectric, electromechanical, and high-field strain behaviors also were studied as a function of temperature and discussed  相似文献   

18.
Ba0.5Sr0.5TiO3 single-layered and multilayered films were epitaxially grown on a (001) LaAlO3 substrate using single target and dual target pulsed laser deposition, respectively. Compared to the single-layered films, the multilayered films exhibited broader phase transition and improved thermo-stability. The microstructure of these epitaxial films was investigated using high-resolution transmission electron microscopy in details. Misfit and threading dislocations were observed in the single-layered film, while the threading dislocations were dramatically decreased and no misfit dislocations were found in the multilayered film. It is suspected that the difference in dislocation densities is responsible for the different behaviors of the permittivity with temperature.  相似文献   

19.
(Na0.85K0.15)0.5Bi0.5TiO3 (NKBT) thin films derived from different amounts of Na/K excess content were fabricated via an aqueous sol-gel method on a Pt(111)/Ti/SiO2/Si substrate, and the effect of Na/K excess content on the microstructure and electrical properties of the NKBT thin films was investigated. A second phase appears when Na/K excess content is below 20 mol%. Appropriated Na/K excess can enhance the polarization and dielectric properties due to compensation of Na/K loss that occurred during heat treatment. The 20 mol% excess derived NKBT thin film exhibits the best ferroelectric and dielectric properties with a remnant polarization (Pr) of 13.6 μC/cm2, and a coercive field (Ec) of 104.8 KV/cm, together with a dielectric constant of 406 and a dissipation factor of 0.064. Similar to the dielectric response change with Na/K excess content, the decreasing concentration of charged defects is the main reason resulting in the increase of the piezoelectric property. The film with a 20 mol% excess content exhibited an effective d33? of about 56 pm/V. Also, the NKBT with a 20 mol% excess content exhibits the lowest current density of 5.6 × 10− 5 A/cm2 at 10 V.  相似文献   

20.
The site symmetry of Yb3+ in In0.5Ga0.5P grown by liquid phase epitaxy has been investigated using a polarized luminescence spectroscopic technique. The site symmetry of indium in In0.5Ga0.5P was lowered from Td to C2v resulting from substitution of indium by ytterbium. The lowering symmetry was confirmed by the spectroscopic observation of the splits of Γ8 levels of Td in C2v symmetry. The substitutional site symmetry of Yb3+ in In0.5Ga0.5P, i.e. Ybln3+, was revealed as C2v.  相似文献   

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