Chao Chin Chan

Preparation of Bi-Layered SrBi2Ta2-xVxO9 Ceramics (0.1 ≦ x ≦ 0.4)

V2O5 is used to substitute Ta2O5 site of the SrBi2Ta2O9 ceramics to form SrBi2Ta2-xVxO9 composition, where 0.1 ≤ x ≤ 0.4. The sintering and the dielectric properties of SrBi2Ta2-xVxO9 ceramics have been developed. For all SrBi2Ta2-xVxO9 composition, the crystal intensities of the (0,0,l) planes increase with the increase of sintering temperature and saturate at 1050C-sintered ceramics, and the increase in the crystal intensities of the (0,0,8) and (0,0,10) planes are more obvious. For the same sintering temperature, the crystal intensities of the (0,0,l) planes increase with the increase of V2O5 content and saturate at SrBi2Ta1.7V0.3O9 ceramics. This study will show that the sintering temperature and V2O5 content have large influences on the maximum dielectric constants (εTc) and the Curie temperatures of SrBi2Ta2-xVxO9 ceramics. Introduction The layer structured bismuth compound ferroelectric has the general formula: An-1Bi2BnO3n+3, where A is usually a divalent ion, such as Sr, Ba, or Pb, and B is Ti, Nb, or Ta [1-3]. Within the bismuth family, SrBi2Ta2O9 ceramics had attracted the most attention in the past years [4-7]. Although the polarization of SrBi2Ta2O9 ceramics is less than the competing Pb(Ti,Zr)O3-based materials, the bismuth-layer compounds are much stable to polarization fatigue free property, i.e. almost no charge loss will happen when polarization is reversed many cycles. In the SrBi2Nb2O9 composition, the substitution of Nb2O5 by V2O5 will lower the sintering temperature and produce materials with enhanced dielectric properties that are useful in many applications [8]. In this study, we are interesting to investigate ceramic materials based on SrBi2Ta2O9 composition, V2O5 is used to substitute for Ta2O5 to form the SrBi2Ta2-xVxO9 compositions. Bulk SrBi2Ta2-xVxO9 materials are sintered at different temperature and their morphologies and crystal phases are examined. The temperature-dependent dielectric characteristics are also investigated as a function of sintering temperature and V2O5 content. Experimental Procedures Reagent-grade raw materials of SrCO3, Bi2O3, Ta2O5, and V2O5 with higher than 99.5% purity were used as starting materials, mixed according to the composition SrBi2Ta2-xVxO9 (x = 0.1, 0.2, 0.3, and 0.4, respectively) and ball-milled for 5h with deionized water. After dried and ground, the powder was calcined at 850C for 3h. After calcination and ground again, then polyvinylalcohol (PVA) was added as a binder. The calcining powder was uniaxially pressed into pellets in a steel die. After debindering, sintering of these pellets was preceded from 900C to 1100C for 4h. The crystal structures of the SrBi2Ta2-xVxO9 ceramics were investigated using XRD patterns, and the morphologies were observed by using scanning electronic micrograph (SEM). The sintered ceramics were painted with Ag-Pd paste and sintered at 700C for 15min. Temperature-dependent dielectric characteristics were measured at 1MHz with an oscillating amplitude (50mV) by an HP4194 impedance analyzer, putting the sintered ceramics in a temperature-programmable testing chamber. Key Engineering Materials Online: 2007-04-15 ISSN: 1662-9795, Vols. 336-338, pp 192-195 doi:10.4028/www.scientific.net/KEM.336-338.192

Sintering AlN Ceramics Below 1500°C with MgO-CaO-Al2O3-SiO2 Glass Addition

5~15 wt% MgO-CaO-Al2O3-SiO2 (MCAS, fabricated by sol-gel method) glass is used as the sintering aid of AlN ceramics. The sintering is proceeded from 1350oC~1550oC, scanning electron microscope is used to observe the sintered morphologies and X-ray diffraction pattern are used to confirm the crystal structures. From the SEM observations, as 10wt% and 15wt% MCAS is added, AlN ceramics can be densified at 1500oC and 1450oC, which are much lower than the before studies were. From the X-ray diffraction patterns, the crystal phases of MCAS-AlN ceramics are AlN, Al2O3, and cordierite phases. In this study, the dielectric characteristics of MCAS-AlN ceramics are also developed as a function of MCAS content and sintering temperature.

Low Temperature Sintering (Ba1-xSrx)TiO3 Ceramics by Using CuO-TiO2 Mixture as Sintering Aid

1wt% CuO-TiO2 (molar ratio, CuO/TiO2= 1) mixture is added as the liquid phase sintering aid to develop the sintering and dielectric characteristics of (Ba1-xSrx)TiO3 (x=0, 0.1, and 0.2) ceramics. The crystal characteristics of calcined (Ba1-xSrx)TiO3 powders and sintered (Ba1-xSrx)TiO3 ceramics are developed by using X-ray diffraction method. The calcined (Ba1-xSrx)TiO3 powders and 1050oC-sintered (Ba1-xSrx)TiO3 ceramics reveal a tetragonal or pseudo-cubic structure and the 1150oC-sintered(Ba1-xSrx)TiO3 ceramics reveal a tetragonal structure. Sintered at 1100oC, the (Ba1-xSrx)TiO3 ceramics present a porous structure; Sintered at 1150oC, the (Ba1-xSrx)TiO3 ceramics present a uniform growth. The grain size decreases with the increase of SrO content. In this study, the dielectric characteristics of CuO-TiO2 mixture-fluxed (Ba1-xSrx)TiO3 ceramics are also developed.

Effects of Deposition Parameters and Annealing Temperatures on the Characteristics of the Sr0.6Ba0.4Nb2O6 Thin Films

Sr0.6Ba0.4Nb2O6 (SBN) thin films were prepared by radio frequency (RF) sputtering onto the SiO2/Si/Al and Pt/Ti/Si substrates to form the MFIS and MFM structures. Their deposition rates increased with decreasing oxygen concentration and with increasing RF power. Their optimal deposition parameters were the substrate temperature of 500°C, chamber pressure of 10 mTorr, oxygen concentration of 40%, and RF power of 120W, respectively. The rapid temperature annealing (RTA) process had large effects on the grain growth of the SBN thin films. The effects of different RTA temperatures on the leakage current density - electrical field curves and the capacitance - voltage curves of the SBN thin films were also investigated.

The Influences of NaNbO3 on the Dielectric and Structure Characteristics of (1-X) (Na0.5Bi0.5)TiO3–x NaNbO3 Ceramics

Perovskite-based (1-x) (Na0.5Bi0.5)TiO3-x NaNbO3 [(1-x) NBT-x NN, x = 0.1, 0.2, 0.3 and 0.4] ceramics were sintered at 1080°C. Dielectric characteristics, crystalline structures, and Raman investigations were carried out on (1-x) (Na0.5Bi0.5)TiO3-x NaNbO3 ceramics. X-ray diffraction (XRD) patterns showed that NaNbO3 ceramic would form a solid solution with (Na0.5Bi0.5)TiO3 ceramic, and and unknown or second phases were not observable as well. NaNbO3 ceramic diffused into the crystalline structure of (Na0.5Bi0.5)TiO3 ceramic and (1-x) NBT-x NN ceramics still revealed a rhombohedral structure. The temperature-dielectric constant curves showed that as NN content increased, the temperature to reveal the maximum dielectric constant (Tm) was raised, the depolarization temperature (Td) was shifted to lower value, and the dielectric constant at Tm and the loss tangent at Td gradually decreased. The Raman bands at 770 and 830 cm-1 were attributed to the existence of the oxygen vacancies. In this study, the relaxor-type ferroelectric properties of NBT ceramic had been improved as NN ceramic was added.

The Influences of Annealing Temperatures on the Properties of the Sol-Gel Deposition SrBi4Ti4O15 Thin Films

In this study, SrBi4Ti4O15 (SBT) thin films were deposited onto the SiO2/p-Si(100) and Pt/Ti/SiO2/p-Si(100) substrates by using sol-gel method. After deposition, the SBT thin films were then heated by a rapid thermal annealing (RTA) process conducted in air for 1min at 600-800°C. The surface morphologies and the crystalline structures of the SBT thin films were investigated by using SEM and XRD patterns. The grain sizes increased and the pores decreased with rising RTA temperature. In addition, the coercive field decreased and the remanent polarization and saturation polarization increased with rising RTA temperature. The lnJ-E1/2 curves of the SBT thin films were also investigated to find the leakage current mechanisms correspond either to the Schottky emission or to the Poole-Frenkel emission.

Influence of Deposition Parameters on the Characteristics of AZOY Transparent Conducting Oxide Thin Film

“GfE Coating Materials Company” had developed a novel AZOY transparent conducting oxide (TCO) material that used ZnO as raw material and contained a small amount of Y2O3 and Al2O3. In this study, the AZOY material developed by GfE company is used as the based TCO material and we will develop the influences of substrate temperatures on the characteristics of AZOY TCO films by RF sputtering method, under optimal O2/argon ratio and depositing pressure. After deposition, the sheet resistance of AZOY films is measured with a four point probe, and surface morphology and cross-sections are studied using a field emission scanning electron microscope (FESEM). And finally, the UV-Vis spectrophotometer is used to find the transmittance of AZOY TCO films.

Develop Single-Phase High Dielectric Constant SiO2-Based Composite Gate Dielectric

In this study, we hoped to find the single-phase high dielectric FET gate-used ceramic materials, which will be used in the sputtering method and have the dielectric constants higher than those of SiO2 and Si3N4. TiO2, La2O3 and ZrO2 are mixed with SiO2 to format the (1-x) TiO2-x SiO2, (1-x) ZrO2-x SiO2 and (1-x) La2O3-x SiO2 compositions, where x is dependent on the different raw materials. The all compositions are calcined at 1100oC and sintered at 1400oC~ 1550oC for 2hrs, and the X-ray patterns are used to find the crystal phases of all sintered ceramics. Because of the existence of single-phase, the sintering and dielectric characteristics of 0.3 La2O3-0.7 SiO2 ceramic are further developed.

The Influence of Annealing Temperature on the Characteristics of 0.95 (Na0.5Bi0.5)TiO3-0.05 BaTiO3 Thin Films

In this study, 0.95 (Na0.5Bi0.5)TiO3-0.05 BaTiO3 + 1 wt% Bi2O3 (NBT-BT3) composition sintered at 1200oC for 2h is used as target to deposit the NBT-BT3 thin films. The excess 1wt% Bi2O3 is used to compensate the vaporization of Bi2O3 during the deposition process. Ferroelectric NBT-BT3 thin films are deposited on SiO2/Si and Pt/Ti/SiO2/Si substrates using RF magnetron sputter method using the ceramic target fabricated by ourselves. After depositing under the optimal parameters, the thin films are then heated by a conventional thermal annealing (CFA) process conducted in air at temperatures ranging from 600- 800oC for 60min. The morphologies of NBT- BT3 thin films are observed using SEM the crystalline structures of NBT-BT3 thin films are investigated using XRD patterns. The large memory window and stable leakage current density examination reveals that NBT-BT3 thin films annealed on 600oC are better than other thin films under different CTA temperatures. Finally, the top view and cross-sectional images of SEM, memory windows, leakage currents and polarization characteristics of NBT-BT3 thin films are also well developed.