Papers by Keyword: BZT

Abstract: The thin films of Zr co-doped BT (BZT) with the Zr concentrations of 0, 3%, and 5% have been deposited on the quartz substrates via the sol-gel technique with a spin coater. The microstructure and optical properties of the samples were identified by XRD and UV-Vis Spectrophotometer to investigate the properties influenced by the Zr number modification. The XRD patterns exhibited that the samples were a single-phase tetragonal structure and a shift of (101) peak was observed toward a lower angle with increasing Zr content confirming an enlargement in the lattice parameter and cell volume of the samples. On the other hand, the lattice strain and crystallite sizes reduce together with more Zr content. The optical properties examination demonstrated that the BT and BZT samples were highly transparent (~70-80%) in the visible wavelength and the absorption edges exchanged toward a lower wavelength due to the Zr doping particularly on the BZT5. The refractive index values were high categorized at ~ 4, 3.5, and 3.3 for BT, BZT3, and BZT5, respectively. Moreover, BZT possesses the lowest bandgap (3.57 eV) followed by BT (3.61) and BZT5 (3.72 eV)

Abstract: The intrinsic coercive field is predicted by using Landau Ginzburg theory of ferroelectricity. A routine program created on Delphi platform is used to make simulation of the calculation of hysteresis loops and intrinsic coercive field. There are shifting in the values of intrinsic ferroelectric field of BZT on adding the zirconium composition, and the maximum intrinsic coercive field of BZT is found at 0.25 mol zirconium. The calculation shows that the best intrinsic coercive field is found at 1 mol % dopant.

Abstract: BaZr_xTi_1-xO₃-based (BZT) ceramics with Al₂O₃ and MgO addtives were prepared by the conventional solid state method with BaCO₃, ZrO₂, TiO₂, Al₂O₃ and MgO as raw materials and B₂O₃ and Li₂CO₃ as sintering additive. The morphologies were analysized by scanning electron microscopy (SEM). The dielectric constant and dielectric loss of ceramics were measured by LCR meter. The temperature dependences of dielectric constant were measured by high-low temperature incubator tank and LCR meter at 1 MHz and a temperature range-55 to 125 °C. The tunabilities were tested by C-T-V converter and LCR meter at 1 MHz at room temperature. The results show that with the increase of Zr/Ti, BZT ceramic dielectric constant increases, the loss increases, the Curie temperature moves to a lower temperature, and dielectric bias field coordination is relatively lower. The SEM images show that the grain size reaches about 1-2 μm when the sintering temperature is 1100 °C, and the addition of Al₂O₃ and MgO promote the grain growth and densification of the composite ceramics. The Curie peaks are broadened and depressed with the addition of Al₂O₃ and MgO. The tunability is improved to 9.59% under a DC electric field of 7.0 kV/cm after the addition of Al₂O₃. The dielectric constant and dielectric loss of BaZr_0.25Ti_0.75O₃-30wt%Al₂O₃ and BaZr_0.25Ti_0.75O₃-30wt%MgO are 586, 0.011 and 486, 0.003, respectively. The optimistic dielectric properties make it a promising candidate for the application of tunable capacitors and phase shifters.

Abstract: Nanocrystalline barium zirconium titanate, BaZr_0.4Ti_0.6O₃, was synthesized successfully via the sonochemical process. The effects of reaction time on the precipitation of Ba(Zr,Ti)O₃ particles were investigated briefly. The crystal structure as well as molecular vibrations and morphology were investigated. X-ray diffraction indicated that the powders exhibited a single phase perovskite structure, without the presence of pyrochlore or unwanted phases at the reaction time of 60 min. Nanocrystals were formed before being oriented and aggregated into large particles in aqueous solution under ultrasonic irradiation. A scanning electron microscopy (SEM) photograph showed the BZT powder as spherical in shape with uniform nanosized features.

Abstract: We studied the crystallographic of Barium Zirconium Titanate thin films with Aluminum doped (BZAT). These films were prepared by sol-gel process and followed by spin coating. The sintering temperature is taken at 800°C and 900°C. We found that the crystallographic system of BZAT thin films have tetragonal structure with the lattice parameter slightly changed by various Aluminum partial substitution. When 0.01 Al moles added, the grain size of the films is 29.42 nm at 800°C. The sintering temperature 900°C increased the grain size into 50.95 nm. We also calculated the spontaneous polarization theoretically and we found the optimum value of BZT thin film with 0.01 mole Al heated at 800°C, is 0.143 C/m². This way, we could predict that the film has ferroelectric phase.

Abstract: The aim of this study was to investigate the effect of BaZr_0.05Ti_0.95O₃ (BZT) addition on the microstructure, physical, dielectric and piezoelectric properties of hydroxyapatite (HA), and develop new biomaterials which have potential applications in the support for cellular growth and in the system for bone regeneration. In this case the BaZr_0.05Ti_0.95O₃- HA composites (HABZT) were prepared by conventional sintering method. The BZT were added to HA with ratio 0, 10, 20 and 30 %wt. Then the mixed powders were pressed and subsequently sintered at the temperature ranging from 1150 to 1350°C. The result showed that the dielectric and piezoelectric properties were improved by the addition of BZT. Moreover, the bioactivity of the HA improved with addition of BZT especially at 10% as evident by the formation of bone like apatite layers on the surface of all BCZT composites after soaking in simulated body fluid (SBF) for 15 days. The results confirmed the possibility of using these bioactive composites for treatment within the human body.

Abstract: In this work, (Ba0.65Sr0.35)TiO3 (BST) and Ba(Zr0.20Ti0.80)O3 (BZT) ceramic targets were prepared using the traditional solid-state reaction technique, which were sintered at 1200 °C for 2 h. The thin films of BST, BZT and sandwich structure BST/BZT/BST were grown on Pt/Ti/SiO2/Si(100) and Si(100) substrates by rf-sputtering at 500 °C, respectively. And all samples crystallied at temperatures 650 °C for 30 min in oxygen atmosphere. The cross-sectional images of the thin films were characterized by scanning electron microscope (SEM). The dielectric constant and dissipation factor tan of the BZT, BST and BST/BZT/BST thin films are 680 and 0.030, 240 and 0.021, 85 and 0.018, respectively at 100 kHz. Compared with BST and BZT films, the BST/BZT/BST film has lower dielectric constant and lower dissipation. The remanent polarization (Pr) of the sandwich structure BST/BZT/BST thin film is up to 9.57 μC/cm2, the Pr value is larger than that BST (0.25μC/cm2) film and BZT (8.45μC/cm2) film. The optical properties (refractive index n and extinction coefficient k) of the BST/BZT/BST film on Si(100) substrate were measured by n & k analyzer 2000.

Abstract: Ba_xSr_1-xTiO₃ [(BST), 0£x£1] is a solid solution ferroelectric material exhibiting a large dielectric constant non-linear change with an applied DC electric field. And Ba(Zr_xTi_1-x)O₃ solid solution also has received much attention because of the good tunbality. In this paper, Ba_0.6Sr_0.4(Zr_xTi_1-x)O₃ (x=0.15,0.20,0.25,0.30,) ceramic was obtained by traditional ceramic processing. The structural, surface morphological, dielectric properties, tunable properties of this material as well as the mechanism of their nonlinear dielectric constant under DC electric field were systematically examined. The Zr ions substitution of Ti ions has a strong effect on the grain sizes and the dielectric property. The results show that Ba_0.6Sr_0.4(Zr_xTi_1-x)O₃ (x = 0.2, 0.25,0.3) ceramic is a promising candidate for the DC electric field tunable materials for microwave electronics application, because they exhibit high relative tunability (44%, 48%, 35%, respectively) as the strength of electric field is up to 1.5 kV/mm, and low dielectric loss (0.0026, 0.00044, 0.0015, respectively) at 100 kHz at room temperature. X-ray diffraction analyses indicated that the samples present perovskite phase. Scanning electron microscopy micrograph of sample indicated that the grain size decreased and density increased with Zr concentration increasing.

Abstract: In this study, we investigated that of Al/ Ba(Zr_0.1Ti_0.9)O₃ (BZT)/Pt/Ti/SiO₂/Silicon metal-ferroelectric-metal-insulator-semiconductor (MFM) ferroelectric structures and found the memory effect and capacitance of annealed BZT films during the different annealing temperature. Additionally, the capacitance and leakage current density were about 4.3 nF and 1´10^-6A/cm², respectively. From C-V curves, the ferroelectric properties and charges accumulation of annealed BZT films were also found during the annealing temperature of 700°C.

Abstract: In this work, barium zirconium titanate (BZT) ceramics were fabricated by using a ultrasonic ball milling technique. BZT with the ratio of BaCO3:ZrO2:TiO2 was 1:0.05:0.95 was mixed in ultrasonic ball milling for 1, 3 and 4.5 hr and calcined at temperature of 1000 °C. Phase formation of BZT powder was investigated using XRD technique. Moreover, physical and electrical properties were examined. It was found that the tetragonal structure of BZT can be observed. Particle size of sample powder obtained from new milling technique is smaller than that of powder obtained from conventional mixed oxide method. Moreover, this new technique also requires the less time fabrication. Furthermore, the dielectric properties are increased with milling time and sintering temperature.