Ho-Hua Chung

Study of Different TiO2 Electrode Structures on Dye-Sensitized Solar Cell

In this research, applications of different TiO2 electrode structures on Dye-Sensitized Solar Cell were investigated. The different TiO2 electrode structures include: (1) synthesis of TiO2 nano-particles and TiO2 film electrode by sol-gel and spin-coating method; (2) fabrication of the TiO2 film electrode by RF Sputtering; (3) fabrication of the rod TiO2 electrode by photo lithography. X-ray diffraction patterns show that the best sintering temperature of nano-TiO2 thin film is 500oC, at which TiO2 anatase phase forms best and the smallest particle-size (8-10 nm) can be obtained. Ultraviolet-visible absorption spectra reveal that the rod TiO2 electrode with TCPP sensitizer adsorbed on has the best optical absorption from 400 nm to 700 nm. The results of current-voltage analyses reveal that the solar cell with rod TiO2 electrode has higher conversion efficiency than the others. This result also provides clear evidence for the contact area between TiO2 electrode and TCPP sensitizer plays an important role on the efficiency of dye-sensitized solar cell.

Influence of Excess Bi2O3 on the Characteristics of (Na0.5Bi0.5)TiO3-BaTiO3 Ceramics

In this study, piezoelectric materials 0.95 (Na0.5Bi0.5)TiO3-0.05 BaTiO3 (NBT-BT) composition with excess x wt% Bi2O3 (x=0, 1, 2, and 3) are investigated as a function of sintering temperatures. The sintering characteristics and dielectric characteristics of excess Bi2O3-doped 0.95 (Na0.5Bi0.5)TiO3- 0.05 BaTiO3 ceramics are developed with the aid of SEM, XRD patterns, and dielectric-temperature curves. The sintering process is carried out in air for 2h from 1120oC to 1200oC. Dielectric-temperature properties are investigated in the temperature range of 30oC~350oC at the frequencies of 10KHz~1MHz. The maximum dielectric constants of NBT-BT ceramics first increase with the increase of Bi2O3 content, reach the maximum at 1wt%- Bi2O3-added NBT-BT ceramics, and then decrease with the further increase of Bi2O3 content. The maximum dielectric constants of NBT-BT ceramics are almost unchanged as the measured frequency increases. The Curie temperatures of NBT-BT ceramics are also developed.

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.

The Influences of Excess Bi2O3 Content on the Characteristics of 0.8 (Bi0.5K0.5)TiO3-0.2 BaTiO3 Ceramics

The Bi-layer structure bismuth 0.8 Bi0.5K0.5TiO3-0.2 BaTiO3 + x wt% (0.8 BKT-0.2 BT3-x, x = 0, 1, 2, and 3) Bi2O3 ceramic was sintered in air for 2 h from 1000°C to 1100°C. The excess content of Bi2O3 was used as the sintering aid and to compensate the vaporization of Bi2O3 during the sintering process. A narrow range of sintering temperature could be used to densify the 0.8 BKT-0.2 BT3-x ceramics. The addition of excess Bi2O3 would lower down the sintering temperature and extend the temperature range to sinter the 0.8 BKT-0.2 BT3-x ceramics. The Curie temperatures of 0.8 BKT-0.2 BT3-x ceramics would be shifted to lower temperatures as the sintering temperatures and the content of excess Bi2O3 increase.

Electrical and Physical Characteristics of Ba(Zr0.1Ti0.9)O3 Thin Films under Oxygen Plasma Treatment for Nonvolatile Memory Devices Application

In this study, the effects of oxygen gas plasma on the surface treatment of Ba(Zr0.1Ti0.9)O3 (BZT) films are investigated. The influence of plasma on the structure is developed by using X-ray diffraction patterns and the electrical characteristics are developed by using the MIM and MFIS capacitor structure. Experiment results clearly indicate that the electrical characteristics of BZT film have improved effectively within oxygen plasma surface treatment.

Sintering and Dielectric Properties of Excess Bi2O3 Doped BaBi2Nb2O9 Ceramics

In this study, ferroelectric materials with Bi-layered structure BaBi2Nb2O9 with excess x wt% Bi2O3 (x=0, 1.5, and 3) are investigated as the main compositions, and the sintering is proceeded from 1000oC~1100oC. The effect of Bi2O3 on the morphologies, crystal structure, and dielectric characteristics of BaBi2Nb2O9 ceramics is developed with the aid of SEM, X-ray diffraction, and dielectric-temperature curves. Dielectric properties are investigated in the temperature of 25oC~ 465oC at frequency 10KHz~1MHz. It is found that sintering temperature and Bi2O3 content has no apparent influence on the Curie temperatures, but they have large influence on the maximum dielectric constants.

The Nonlinear Characteristics of Different Additives Added V2O5-ZnO Varistor

Most commercial ZnO varistors containing Bi2O3 exhibit excellent varistor properties, but they have a few drawbacks due to Bi2O3 having high volatility and reactivity and higher sintering temperature. In this study, V2O5 is added as the varistor forming oxide to lower down the sintering temperature of ZnO varistors for the further developing the chip Varistor array by using the Ag as the inner electrode. It is found that the sintering temperature of V2O5-added ZnO will be lower down to about 600oC. But the addition of V2O5 has no improvement in the electrical characteristics, and they need many additives to obtain the high performance. For that, the nonlinear properties in these Varistors can be improved by incorporation of some oxide additives. Different MnOx oxides (MnO, MnO2, and Mn3O4) and CoOx oxides (CoO and Co3O4)are used as the minor oxide additives. The influences of different MnOx and CoOx oxides on the nonlinear voltage–current density (V-I) characteristics and the nonlinear exponent (α) of V2O5-ZnO varistor will be well developed.