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1.
Ferroelectric and leakage properties are important for ferroelectric applications. Pure and Nd-doped (x=0.05-0.20) BiFeO3 thin films were fabricated by sol-gel method on FTO substrates. The phase structure, surface morphology, leakage current, ferroelectric properties, and optical properties of BiFeO3- based thin films were investigated. The substitution of Nd3+ ions for the Bi3+ site converts the structure from rhombohedral to coexisting tetragonal and orthorhombic. Nd doping improves the crystallinity of BiFeO3 thin films. The leakage current of Nd-doped BiFeO3 decreases by two to three orders of magnitude compared with that of pure BiFeO3. Among the samples, 15% Nd-doped BiFeO3 exhibits the strongest ferroelectric polarization of 17.96 μC/cm2. Furthermore, the absorption edges of Bi1-xNd x FeO3 thin films show a slight red-shift after Nd doping. 相似文献
2.
Various lead-free ceramics have been investigated in search for new high-temperature dielectrics. In particular, Bi4Ti3O12 is a type of ferroelectric ceramics, which is supposed to replace leadcontaining ceramics for its outstanding dielectric properties in the near future. Ferroelectric ceramics of Bi4Ti3O12 made by conventional mixed oxide route have been studied by impedance spectroscopy in a wide range of temperature. X-ray diffraction patterns show that Bi4Ti3O12 ceramics are a single-phase of ferroelectric Bi-layered perovskite structure whether it is calcined at 800 °C or after sintering production. This study focused on the effect of the grain size on the electric properties of BIT ceramics. The BIT ceramics with different grain sizes were prepared at different sintering temperatures. Grain becomes coarser with the sintering temperature increasing by 50 °C, relative permittivity and dielectric loss also change a lot. When sintered at 1 100 °C, r values peak can reach 205.40 at a frequency of 100 kHz, the minimum dielectric losses of four different frequencies make no difference, all close to 0.027. The values of E a range from 0.52 to 0.68 eV. The dielectric properties of the sample sintered at 1 100 °C are relatively better than those of the other samples by analyzing the relationship of the grain, the internal stresses, the homogeneity and the dielectric properties. SEM can better explain the results of the dielectric spectrum at different sintering temperatures. The results show that Bi4Ti3O12 ceramics are a kind of dielectrics. Thus, Bi4Ti3O12 can be used in high-temperature capacitors and microwave ceramics. 相似文献
3.
The Cu x Si1-x thin films have been grown by pulsed laser deposition (PLD) with in situ annealing on Si (001) and Si (111), respectively. The transformation of phase was detected by X-ray diffraction (XRD). The results showed that the as-deposited films were composed of Cu on both Si (001) and Si (111). The annealed thin films consisted of Cu + η”-Cu3Si on Si (001) while Cu + η’-Cu3Si on Si (111), respectively, at annealed temperature (T a) = 300-600 °C. With the further increasing of T a, at T a= 700 °C, there was only one main phase, η”-Cu3Si on Si (001) while η’-Cu3Si on Si (111), respectively. The annealed thin films transformed from continuous dense structure to scattered-grain morphology with increasing T a detected by field emission scanning electron microscope (FESEM). It was also showed that the grain size would enlarge with increasing annealing time (t a). 相似文献
4.
付承菊 《武汉理工大学学报(材料科学英文版)》2008,23(5):622-624
The Bi4Ti3Oi2 and Bi3.25La0.75Ti3O12 thin films were prepared on the Pt/Ti/SiO2/Si substrate using the sol-gel method. The effect of La doping on the microstructure and ferroelectric properties of Bi4Ti3O12 films were investigated. Both the Bi4Ti3O12 and Bi3.25La0.75Ti3O12 thin films exhibited typical bismuth layered perovskite structure. The 2Pr (remanent polarization) value of Bi3.25La0.75Ti3O12 thin films is 18.6 μC/cm^2, which is much larger than that of Bi4Ti3O12 thin films. And the Bi3.2eLa0.75Ti3O12 films show fatigue-free behavior, while the Bi4Ti3O12 thin films exhibit the fatigue problem. The mechanism of improvement of La doping was discussed. 相似文献
5.
Crystal growth,structure and properties of bismuth triborate BiB<Subscript>3</Subscript>O<Subscript>6</Subscript> crystal 总被引:1,自引:0,他引:1
BiB3O6 (BIBO) single crystals with size of 46×23×10 mm3 and weight of 26.0 g have been successfully grown by top-seeded method. Problems encountered in the growth process of this crystal have been discussed in detail, and the methods of growing high-quality large crystals have been put forward. The relationship between their structure and properties is studied. The space group of monoclinic BiB3O6 is C2 and the cell parameters are a=7.1203(7) Å, b=4.9948(7) Å, c=6.5077(7) Å, β=105.586(8)″, and V=222.93(5) Å3. The density of BIBO is 4.8965 g/cm3. The Mohs’s scale of hardness is 5.5–6. There is no cleavage face in the crystal. The transmittance of BIBO is about 80 percent in the range from visible coherent light to near-infrared light. The ultraviolet cutoff wavelength is at 276 nm. BiB3O6 is a biaxial crystal and has two sets of axes, and the relative orientation of (X, Y, Z) with regard to (a, b, c) is: X//b, (Y, c)=47.2°, (Z, a)=31.6°, determined by X-ray analysis combined with polarized microscopy. Second-harmonic-generation (SHG) experiments were carried out for the first time. In type I phase-matching (PM) directions (11.1°, 90°) and (168.9°, 90°), SHG conversion efficiencies of two directions for 1.064 μm light are up to 67.7% and 58%, respectively. We have also obtained the third-harmonic-generation (THG) of 1.064 μm. The comparative experiments between BIBO and KTP were carried out on conversion efficiency, transmittance and hardness. All the above results indicate that BiB3O6 is a kind of excellent nonlinear optical (NLO) crystal. 相似文献
6.
王华 《武汉理工大学学报(材料科学英文版)》2016,31(6):1230-1234
ZnMn2O4 films for resistance random access memory (RRAM) were fabricated with different device structures by magnetron sputtering. The effects of electrode on I-V characteristics, resistance switching behavior, endurance and retention characteristics of ZnMn2O4 films were investigated. The ZnMn2O4 films, using p-Si and Pt as bottom electrode, exhibit bipolar resistive switching (BRS) behavior dominated by the space-charge-limited conduction (SCLC) mechanism in the high resistance state (HRS) and the filament conduction mechanism in the low resistance state (LRS), but the ZnMn2O4 films using n-Si as bottom electrodes exhibit both bipolar and unipolar resistive switching behaviors controlled by the Poole-Frenkel (P-F) conduction mechanism in both HRS and LRS. Ag/ZnMn2O4/p-Si device possesses the best endurance and retention characteristics, in which the number of stable repetition switching cycle is over 1000 and the retention time is longer than 106 seconds. However, the highest R HRS/R LRS ratio of 104 and the lowest V ON and V OFF of 3.0 V have been observed in Ag/ZnMn2O4/Pt device. Though the Ag/ZnMn2O4/n-Si device also possesses the highest R HRS/R LRS ratio of 104, but the highest values of V ON,V OFF, R HRS and R LRS, as well as the poor endurance and retention characteristics. 相似文献
7.
c-axis-oriented SmBa_2Cu_3O_7(SmBCO) films have been deposited on(100)- LaA1O_3(LAO)substrate by metal organic chemical vapor deposition(MOCVD) technique.The effects of deposition temperature(T_(dep)) and total pressure(P_(tot)) on the orientation and microstructure of SmBCO films were investigated.The orientation of SmBCO films transformed from α-axis to c-axis with increasing of T_(dep) from 900 to 1 100℃.At T_(dep)=1 050℃,SmBCO films had c-axis orientation and tetragon surface.At P_(tot)~(dep)=400-800 Pa and T_(dep)=1 050 ℃,totally c-axis-oriented SmBCO films were obtained.The R_(dep) of SmBCO films increased firstly and then decreased with increasing P_(tot).The surface of SmBCO films exhibited tetragon morphology at 1 050 ℃ and400 Pa.Maximum thickness of SmBCO film deposited was 1.2μm at P_(tot)= 600 Pa,and the corresponding R_(dep)was 7.2 μm·h~(-1). 相似文献
8.
贺海燕 《武汉理工大学学报(材料科学英文版)》2009,24(3):359-362
Fatigue-free Bi3.2La0.8Ti3O12 ferroelectric thin films were successfully prepared on p-Si (100) substrates using metalorganic solution deposition process. The orientation and formation of 5-layers thin films
were studied under different processing conditions using XRD. Experimental results indicate that increase in annealing time
at 700 °C after preannealing for 10 min at 400 °C can remarkably increase (200)-orientation of the films derived from the
precursor solutions with two contents of citric acid. Meanwhile, high content of citric acid increases the film thickness
and is conducive to the a-orientation of the films with the preannealing, and low concentration of the solution is conducive to the c-orientation of
the films without the preannealing. 相似文献
9.
吴浪 《武汉理工大学学报(材料科学英文版)》2015,30(4):724-728
CuO-doped (Ag0.75Li0.1Na0.1K0.05)NbO3 (ALNKN-xCuO, x = 0–2mol%) lead-free piezoelectric ceramics were prepared by the solid-state reaction method in air atmosphere. The effects of CuO addition on the phase structure, microstructure, and piezoelectric properties of the ceramics were investigated. The experimental results show that the ALNKN ceramics without doping CuO possess rhombohedral phase along with K2Nb6O16-type phase and metallic silver phase. For all of the CuO-doped ALNKN ceramics, a pure perovskite structure with the orthorhombic phase was obtained by enclosing the samples in a corundum tube. A homogeneous microstructure with the grain size of about 1 μm was formed for the ceramics with 0.5mol% CuO. The grain size increases with increasing amount of CuO. The temperature dependence of dielectric properties indicates that the ferroelectric phase of the ALNKN-xCuO ceramics becomes less stable with the addition of CuO. The ceramics with x = 1mol% exhibit relatively good electrical properties along with a high Curie temperature. These results will provide a helpful guidance to preparing other AN-based ceramics by solid-state reaction method in air atmosphere. 相似文献
10.
(Ba0.6Sr0.4)0.85Bi0.1TiO3 ceramics doped with x wt%CaZrO3 (x= 0-10) were synthesized by solid-state reaction method. The effects of CaZrO3 amount on the dielectric properties and structure of (Ba0.6Sr0.4)0.85Bi0.1TiO3 ceramics were investigated. X-ray diffraction results indicated a pure cubic perovskite structure for all samples and that the lattice parameter increased till x=5 and then slightly decreased. A homogenous microstructure was observed with the addition of CaZrO3. Dielectric measurements revealed a relaxor-like characteristic for all samples and that the diffusivity γ reached the maximum value of 1.78 at x=5. With the addition of CaZrO3, the dielectric constant dependence on electric field was weakened, insulation resistivity enhanced and dielectric breakdown strength improved obviously and reached 19.9 kV/mm at x=7.5. In virtue of low dielectric loss (tan δ<0.001 5), moderate dielectric constant (εr >1 500) and high breakdown strength (Eb >17.5 kV/mm), the CaZrO3 doped (Ba0.6Sr0.4)0.85Bi0.1TiO3 ceramic is a potential candidate material for high power electric applications. 相似文献
11.
Effect of oxygen partial pressure on epitaxial growth and properties of laser-ablated AZO thin films
Al-doped ZnO (AZO) thin films were grown on c-sapphire substrates by laser ablation under different oxygen partial pressures (P O2). The effect of PO2 on the crystal structure, preferred orientation as well as the electrical and optical properties of the films was investigated. The structure characterizations indicated that the as-grown films were single-phased with a wurtzite ZnO structure, showing a significant c-axis orientation. The films were well crystallized and exhibited better crystallinity and denser texture when deposited at higher P O2. At the optimum oxygen partial pressures of 10 - 15 Pa, the AZO thin films were epitaxially grown on c-sapphire substrates with the (0001) plane parallel to the substrate surface, i e, the epitaxial relationship was AZO (000 1) // Al2O3 (000 1). With increasing P O2, the value of Hall carrier mobility was increased remarkably while that of carrier concentration was decreased slightly, which led to an enhancement in electrical conductivity of the AZO thin films. All the films were highly transparent with an optical transmittance higher than 85 %. 相似文献
12.
Guo DongYun Li MeiYa Liu Jun Yu BenFang Pei Ling Wang YunBo Yu Jun Yang Bin 《中国科学E辑(英文版)》2008,51(1):10-15
We have investigated the preparation and properties of Bi3.4Ce0.6Ti3O12 thin films. The Bi3.4Ce0.6Ti3O12 thin films were fabricated on the Pt/Ti/SiO2/Si substrates using sol-gel method. The structure and morphology of the films were characterized using X-ray diffraction
and atomic force microscopy. The thin films showed a perovskite phase and dense microstructure. The dielectric constant and
the dissipation factor of the Bi3.4Ce0.6Ti3O12 thin films were about 172 and 0.031 at 1 kHz, respectively. The 2P
r and 2E
c of the Bi3.4Ce0.6Ti3O12 thin films were 67.1 μC/cm2 and 299.7 kV/cm, respectively, under an applied field of 600 kV/cm. The Bi3.4Ce0.6Ti3O12 film did not show fatigue up to 4.46×109 switching cycles at a frequency of 1 MHz, and showed good insulating behavior according to the test of leakage current.
Supported by the Natural Science Foundation of Hubei Province (Grants No. 2004ABA082) 相似文献
13.
张光富 《武汉理工大学学报(材料科学英文版)》2018,33(3):566-570
The spontaneous magnetic transitions and corresponding magnetoelastic properties of intermetallic compounds RMn2Ge2 (R=Gd, Tb and Dy) were investigated by using the X-ray diffraction method and magnetic measurement. The results showed that the compounds experience two magnetic transitions, namely the second-order paramagnetic to antiferromagnetic transition at temperature TN (TN=368, 423 and 443 K for GdMn2Ge2, TbMn2Ge2 and DyMn2Ge2, respectively) and the first-order antiferromagnetic - ferrimagnetic transition at temperature Tt (Tt=96, 80 and 40 K for GdMn2Ge2, TbMn2Ge2 and DyMn2Ge2, respectively) as the temperature decreases. The temperature dependence of the lattice constant a(T) displays a negative magnetoelastic anomaly at the second-order transition point TN and, at the first-order transition Tt, a increases abruptly for GdMn2Ge2 and TbMn2Ge2, Δa/a about 10-3. Nevertheless, the lattice constant c almost does not change at these transition points indicating that such magnetoelastic anomalies are mainly contributed by the Mn-sublattice. The transitions of the magnetoelastic properties are also evidenced on the temperature dependence of magnetic susceptibility χ. The first-order transition behavior at Tt is explained by the Kittel mode of exchange inversion. 相似文献
14.
We put forward a first-principles density-functional theory about the impact of pressure on the structural and elastic properties of bulk CaN2, SrN2 and BaN2. The ground state properties of three alkaline earth diazenides were obtained, and these were in good agreement with previous experimental and theoretical data. By using the quasi-harmonic Debye model, the thermodynamic properties including the debye temperature Θ D, thermal expansion coefficient α, and grüneisen parameter γ are successfully obtained in the temperature range from 0 to 100 K and pressure range from 0 to 100 GPa, respectively. The optical properties including dielectric function ε(?), absorption coefficient α(?), reflectivity coefficient R(?), and refractive index n(?) are also calculated and analyzed. 相似文献
15.
Guo DongYun Li MeiYa Liu Jun Pei Ling Yu BenFang Zhao XingZhong Yang Bin Wang YunBo Yu Jun 《中国科学E辑(英文版)》2007,50(4):472-477
The Bi4Zr0.5Ti2.5O12 (BZT) thin films were fabricated on the LaNiO3 bottom electrode using sol-gel method. The structure and morphology of the films were characterized using X-ray diffraction, AFM and SEM. The results show that the films have a perovskite phase and dense microstructure. The 2Pr and 2Vc of the Pt/BZT/LaNiO3 capacitor are 28.2 μC/cm2 and 14.7 V respectively at an applied voltage of 25 V. After the switching of 1×1010 cycles, the Pr value decreases to 87% of its pre-fatigue values. The dielectric constant (ε) and the dissipation factor (tanδ) of the BZT thin films are about 204 and 0.029 at 1 kHz, respectively. The films show good insulating behavior according to the test of leakage current. The clockwise C-V hysteresis curve observed shows that the Pt/BZT/LaNiO3 structure has a memory effect because of the BZT film's ferroelectric polarization. 相似文献
16.
The electronic structures of bulk Bi2Te3 crystals were investigated by the first-principles calculations. The transport coefficients including Seeback coefficient and power factor were then calculated by the Boltzmann theory, and further evaluated as a function of chemical potential assuming a rigid band picture. The results suggest that p-type doping in the Bi2Te3 compound may be more favorable than n-type doping. From this analysis results, doping effects on a material will exhibit high ZT. Furthermore, we can also find the right doping concentration to produce more efficient materials, and present the “advantage filling element map” in detail. 相似文献
17.
王衍行 《武汉理工大学学报(材料科学英文版)》2016,31(5):961-964
The effect of Ga2O3 on the structure and properties of calcium aluminate glasses fabricated by vacuum melting process was investigated by Raman spectrum, differential scanning calorimeter (DSC), and infrared spectrum methods. The results show that calcium aluminate glass network only consists of [AlO4] tetrahedral units. With the gradual addition of Ga2O3, the quantity of [GaO4] tetrahedral units increases. Substitution of Ga2O3 for Al2O3 results in a decrease in T g T x, and T p, and an increase in the thermal stable index ΔT. Similarly, the absorption band around 3.0 μm obviously reduces and the transparency in 4.0-6.0 μm rapidly increases with increasing Ga2O3 content. However, the chemical stability of calcium aluminate glasses decreases if Ga2O3 is introduced due to the increasing of [GaO4] units in the glass network. 相似文献
18.
High performance piezoelectric ceramics with high Curie temperatures(TC) are the bottle necks of relevant high temperature devices. In this study, the electrical performance and microstructure of Li and Mn codoped Aurivillius-type composite ceramics with a composition Ca_(0.99-x_Bi_(6.99+x)(Li Mn)_(0.01) Nb Ti_5O_(24)(x = 0–0.8) were systematically investigated. The results indicated that uniform intergrowth structure with a lattice similar to that of the end member CBT could be formed at a low x value(x 0.4). Phase separation occurred when more A-site Ca~(2+) ions were replaced by Bi~(3+) ions. Nevertheless, all composite samples showed d_(33) values about 2 to 3 times of that of the constituent phase Ca Bi_4Ti_4O_(15) and Bi_3 Ti NbO_9 with still a high depolarization temperature. The performance of the samples was found to be related to the density and larger lattice distortion along the polarization a axis. The results also demonstrated that formation of the compound system was an effective way in improving the performance of Aurivillius-type high TC piezoelectric ceramics. 相似文献
19.
Amorphous La0.7Zn0.3MnO3 (LZMO) films were deposited on p+-Si substrates by sol-gel method at low temperature of 450 °C. The Ag/LZMO/p+-Si device exhibits invertible bipolar resistive switching and the R HRS/R LRS was about 104-106 at room temperature which can be kept over 103 switching cycles. Better endurance characteristics were observed in the Ag/LZMO/p+-Si device, the V Set and the V Reset almost remained after 103 endurance switching cycles. According to electrical analyses, the conductor mechanism was in low resistor state (LRS) governed by the filament conductor and in the high state (HRS) dominated by the traps-controlled space-charge-limited current (SCLC) conductor. 相似文献
20.
MeiYa Li Ling Pei Jun Liu BenFang Yu DongYun Guo XiaoHua Sun XingZhong Zhao 《中国科学E辑(英文版)》2008,51(11):1843-1849
Ferroelectric Bi3.25La0.75Ti3O12 (BLT) and Bi3.15Nd0.85Ti3O12 (BNT) thin films were fabricated on Pt/TiO2/SiO2/Si (100) substrates by a modified sol-gel technique. X-ray diffraction indicated that these films were of single phase with
random polycrystalline orientations. The surface morphologies of the films were observed by scanning electron microscope,
showing uniform, dense films with grain size of 50–100 nm. Well-saturated hysteresis loops of the films were obtained in metal-ferroelectric-metal
type capacitors with Cu top electrodes at an applied voltage of 400 kV/cm, giving the remanent polarization (2P
r) and coercive field (2E
c) values of the films of 25.1 μC/cm2 and 203 kV/cm for BLT, and 44.2 μC/cm2 and 296 kV/cm for BNT, respectively. Moreover, these capacitors did not show fatigue behaviors after up to 1.75×1010 switching cycles at the test frequency of 1 MHz, suggesting a fatigue-free character. The influences of the La3+ and Nd3+ doping on the properties of the films were comparatively discussed.
Supported by the National Key Basic Research and Development Program of China (Grant No. 2006CB932305) and the Natural Science
Foundation of Hubei Province, China (Grant No. 2004ABA082) 相似文献