158 resultados para PZT ceramics


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制备了高质量的Yb:YAG透明陶瓷.Yb:YAG透明陶瓷的晶粒尺寸为10μm左右且分布均匀,晶界处和晶粒中没有杂质、气孔的存在.Yb:YAG样品中所有元素分布均匀,不同的晶粒间,晶粒和晶界间成分是一致的,没有出现成分的偏析.4mm厚样品的透过率为80%.LD泵浦获得了波长为1030nm,最大功率为268mW的连续激光输出.

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采用传统无压烧结工艺制备了Er^3+/Yb^3+共掺的氧化镧钇透明陶瓷并对其光谱性能进行了研究.样品具有较大的吸收和发射截面.La2O3的添加使样品的荧光寿命(τs)与玻璃接近,当Yb^3+和Er^3+的掺杂量分别为5at%和0.5at%时,测得τs=9.65ms.这种荧光寿命长、发射截面大和线宽窄的特性有利于微型、可集成化和大功率激光输出的实现.

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研究了La2O3对Yb:Y2O3透明陶瓷光谱性能的影响,添加适量La2O3以后,Yb:Y2O3透明陶瓷的吸收峰和发射峰的位置不变,但由于La^3+的离子半径大于Y^3+的离子半径,在Y2O3中引入La^3+离子后,导致Y2O3晶格常数变大,晶场强度变弱,同时降低了Y2O3晶体的有序度,致使发射峰强度有所下降,发射截面变小.过量的№La2O3(x=0.16)造成yb^3+激活离子发射强度明显下降;其荧光寿命在添加La2O3后总体增大45%-60%.

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Luminescence characteristics of Yb3+, La3+ codoped yttrium oxide nanopowders were investigated. The grain size and the crystallinity of (Yb0.05Y0.90La0.05)(2)O-3 nanopowders increase with the increase of calcination temperature. The average grain size of the nanopowders calcined at 1100 degrees C is 66 nm and its cooperative up-conversion luminescence centered at 498 nm was detected due to nanometer size effect and perfect crystallinity. However, the cooperative up-conversion luminescence of (Yb0.05Y0.90La0.05)(2)O-3 transparent ceramics was not detected. (c) 2008 Elsevier B.V. All rights reserved.

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本发明涉及振动检测技术领域,公开了一种用于振动检测的调制解调系统及方法。该系统包括振动测量的光路系统部分和后期振动信号解调部分,利用该振动测量的光路系统部分中的PZT驱动电源对PZT产生的固定角频率ω0振动,从而实现对参考光进行相位调制,调制后的参考光与载有振动信息的信号光发生拍频,通过后期振动信号解调部分对拍频信号的解调来检测物体表面的微小振动。利用本发明提供的这种用于振动检测的调制解调系统及方法,光路结构简单,利用了PZT的振动产生一个固有的相位调制,后期通过相位解调,可以检测出物体表面的微小振动,此方法具有高精度、非接触、频率响应快等显著特点。

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We report on improved electrical properties of lead zirconate titanate (PZT) film deposited on titanium metal foil using nitrogen annealing. After nitrogen annealing of the PZT capacitors, symmetric capacitance-voltage (C-V) characteristics, higher dielectric constant and breakdown field, less change of dielectric constant with frequency, lower dielectric loss and leakage current are obtained. (C) 2003 Elsevier B.V. All rights reserved.

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The influence of gamma-radiation dose rate on the electrical properties of lead zirconate titanate capacitors was investigated. More severe degradations in dielectric constant, coercive field, remanent polarization and capacitance-voltage (C-V) curves occurred with increasing radiation dose at lower dose rates. The electrical properties exhibited distinct radiation dose rate dependence and the worst-case degradation occurred at the lowest dose rate. The radiation-induced degradation of parameters such as the coercive field drift and distortion of the C-V curve can be recovered partly through post-irradiation annealing.

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La2Zr2O7是一种近年来才提出的新型热障涂层材料,该材料熔点高,在熔点以下不发生相变,热导率低,抗烧结及没有氧传输发生,这些特点使得它作为一种高温下应用的热障涂层材料越来越引起人们的重视。但是,由于该材料的热膨胀系数和断裂韧性比较低,它的实际应用受到了限制。 在本论文中,使用高压烧结的方法获得了致密化的纳米La2Zr2O7块体材料,并对其断裂韧性和热膨胀系数进行了研究。得到的La2Zr2O7纳米材料的断裂韧性和热膨胀系数分别为1.98MPam1/2和9.6×10-6K-1 (200-1000℃),这些数值明显高于非纳米的La2Zr2O7陶瓷(断裂韧性和热膨胀系数分别为1.40 MPam1/2 和 9.1×10-6 K-1,该结果表明纳米化是一种提高材料断裂韧性和热膨胀系数的有效方法。在La2Zr2O7纳米粉末中加入8YSZ纳米颗粒,高压烧结后使其颗粒充分生长,在得到的复相化合物中观察到形成了类似棒状晶体的自增韧相,使得复合材料的断裂韧性(1.88 MPam1/2)比La2Zr2O7有所提高,甚至超过了同样条件下制备的8YSZ样品的断裂韧性。 La2Zr2O7的断裂韧性也可以通过在基体中添加BaTiO3铁电材料得到明显的提高。当添加BaTiO3的体积含量达到10vol%时,4.5GPa,1450℃高压烧结10min得到的复合材料断裂韧性达1.98 MPam1/2,明显高于同条件下烧结的La2Zr2O7 (1.60MPam1/2)。应力诱导下BaTiO3的电畴转向是主要的增韧原因。随着BaTiO3颗粒添加的体积含量增加,复相化合物的热膨胀系数也明显提高。当掺杂20vol%BaTiO3时,得到的复合材料平均热膨胀系数达到10.2×10-6K-1 (150~1200℃)。 我们通过在4.5GPa, 1650℃高压烧结5min的方法还获得了掺杂YAG纳米颗粒的La2Zr2O7纳米复相陶瓷。在室温下测量了材料的维氏硬度,并通过压痕裂纹长度计算出了材料的断裂韧性。随着YAG纳米颗粒体积含量的增加,纳米复相陶瓷的断裂韧性和维氏硬度都依次增加,当添加20vol%的YAG纳米颗粒时达到最大,分别为1.93 MPam1/2和11.45GPa。断裂韧性增加的机理可归结为以下三点:一是YAG纳米颗粒的添加提高了La2Zr2O7基体的晶界强度,二是基体晶粒尺寸变化的影响,三是YAG纳米颗粒对裂纹的偏转和钉扎作用。添加微米YAG颗粒的复相化合物因为和纳米复相陶瓷具有不同的增韧机制,因此断裂韧性的变化趋势也不相同,在掺入10vol%的YAG微米颗粒时,复合材料的断裂韧性最大,而后降低,当掺入YAG微米粒子的体积含量达到20vol%时,断裂韧性甚至低于La2Zr2O7。 从20世纪90年代开始,电纺作为一种合成纤维的办法越来越吸引人们的注意。其合成的纤维长度长,直径均匀,并且组成范围很广。最初,电纺只是被用来合成一些有机聚合物的纤维,最近,很多研究组开始致力于使用电纺的方法合成复合纤维或者陶瓷纤维。 在本论文中,我们使用电纺的方法获得了La2Zr2O7纳米纤维和SiC单晶纳米线。1000℃煅烧得到的La2Zr2O7纳米纤维具有烧绿石结构,直径在200~500nm之间。同样的温度煅烧时得到的La2Zr2O7纳米纤维的比表面积要明显高于粉末样品的,表明纤维的抗烧结性能比粉末的高。得到的SiC纳米线直径在50~100nm之间,表面有一约5nm厚的无定形的SiO2薄层。 使用电纺的方法,恰当的控制煅烧条件,我们获得了La2Ce2O7, La2(Zr0.745Ce0.386)2O7.524和8YSZ中空纤维。这种中空结构减小了粒子之间的接触面积,提高了材料的抗烧结性能。在扫描电镜分析的基础上,我们总结了这些中空纤维的形成过程。

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Ilmenite-type (Zn1-xCdx)TiO3 (0 <= x <= 0.15 and 0.8 <= x <= 1.0) was synthesized by a modified sol-gel route including the Pechini process via two-step heat treatments. The thermal stability of (Zn1-xCdx)TiO3 depended on the amount of cadmium content. The as-synthesized (Zn1-xCdx)TiO3 (0 <= x <= 0.15 and 0.8 <= x <= 1.0) showed higher thermal stability than that of ZnTiO3. The variation of the dielectric constant of all synthesized (Zn1-xCdx)TiO3 samples for all measurement frequencies showed a similar tendency.

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Oxide ceramics with high sintering-resistance above 1473 K have very important applications in thermal barrier coatings (TBCs), catalytic combustion and high-temperature structural materials. Lanthanum zirconate (La2Zr2O7, LZ) is an attractive TBC material which has higher sintering-resistance than yttria stabilized zirconia (YSZ), and this property could be further improved by the proper addition of ceria.

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La2Zr2O7 (LZ) is a promising thermal barrier coating material for the high-temperature applications, which could be significantly toughened by the BaTiO3 piezoelectric phase incorporated into the matrix. The composites of xBaTiO(3)/(l-x)LZ (x=5, 10, 15, 20 vol%, LZ-x-BaTiO3) were densified by means of high-pressure sintering (HPS) under a pressure of 4.5 GPa at 1450 degrees C for 10 min, by which a high relative density above 93% could be obtained.

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Lanthanum zirconate (La2Zr2O7, LZ) powders with the addition of various Y2O3 contents for potential thermal barrier coatings (TBCs) application were synthesized by solid-state reaction. The structure evolution, sintering-resistance and thermophysical properties of the synthesized powders and sintered ceramics were systematically studied. X-ray diffraction (XRD) results indicate that LZ containing 3-12 wt.% Y2O3 mainly keeps a pyrochlore-type structure, and two new phases of LaYO3 and Y0.18Zr0.82O1.91 are also detected. Raman spectra confirm that the higher the Y2O3 content, the easier is the formation of LaYO3.

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Thermal barrier coatings (TBCs) of La2Zr2O7 (LZ) with the addition of 3 wt.% Y2O3 (LZ3Y) were deposited by electron beam-physical vapor deposition (EB-PVD). The phase stabilities, thermophysical and mechanical properties, and chemical compositions of these ceramics and coatings were studied in detail. The phase stability and thermal expansion behavior of LZ3Y bulk material are identical to those of LZ bulk material, but the mechanical properties of the former are superior to those of the latter. Elemental analysis and X-ray diffraction indicate that compositional deviation of LZ coating can be optimized after doping by 3 wt.% Y2O3, Y2O3 acts as a dopant as well as a process regulator. The optimal composition of LZ3Y coating could be effectively achieved by the addition of excess Y2O3 into the ingot and by properly controlling the current of electron beam (i.e. similar to 650 mA).

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Nanohydroxyapatite (op-HA) surface-modified with L-lactic acid oligomer (LAc oligomer) was prepared by LAc oligomer grafted onto the hydroxyapatite (HA) surface. The nanocomposite of op-HA/PLGA with different op-HA contents of 5, 10, 20 and 40 wt.% in the composite was fabricated into three-dimensional scaffolds by the melt-molding and particulate leaching methods. PLGA and the nanocomposite of HA/PLGA with 10 wt.% of ungrafted hydroxyapatite were used as the controls. The scaffolds were highly porous with evenly distributed and interconnected pore structures, and the porosity was around 90%. Besides the macropores of 100-300 mu m created by the leaching of NaCl particles, the micropores (1-50 mu m) in the pore walls increased with increasing content of op-HA in the composites of op-HA/PLGA. The op-HA particles could disperse more uniformly than those of pure HA in PLGA matrix. The 20 wt.% op-HA/PLGA sample exhibited the maximum mechanical strength, including bending strength (4.14 MPa) and compressive strength (2.31 MPa). The cell viability and the areas of the attached osteoblasts on the films of 10 wt.% op-HA/PLGA and 20 wt.% op-HA/PLGA were evidently higher than those on the other composites.

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SiO2-CaO-P2O5 ternary bioactive glass ceramic nanoparticles were prepared via the combination of sol-gel and coprecipitation processes. Precursors of silicon and calcium were hydrolyzed in acidic solution and gelated in alkaline condition together with ammonium dibasic phosphate. Gel particles were separated by centrifugation, followed by freeze drying, and calcination procedure to obtain the bioactive glass ceramic nanoparticles. The investigation of the influence of synthesis temperature on the nanopartilce's properties showed that the reaction temperature played an important role in the crystallinity of nanoparticle. The glass ceramic particles synthesized at 55 degrees C included about 15% crystalline phase, while at 25 degrees C and 40 degrees C the entire amorphous nanopowder could be obtained.