Pb-free Glass Research Articles

Piezoresistive Sensor Based on Micrographite-Glass Thick Films.

A new Pb-free glass containing several oxides (Bi2O3, B2O3, SiO2, Al2O3 and ZnO) with sintering temperature reduced down to 600 °C has been developed for applications in a piezoresistive pressure sensor. Using this low sintering temperature glass, it was possible to fabricate micrographite-based pastes and piezoresistive films without losses of graphitic material during the sintering. Good adherence of the films onto alumina substrates was observed and attributed in part to the reactions of ZnO and Bi2O3 with alumina substrates. Piezoresistive films with uniformly distributed micrographite particles were produced using sodium carboxymethyl cellulose (NaCMC) in aqueous solutions during the preparation of pastes. NaCMC plays a decisive role in interactions between micrographite particles and glassy matrix, providing good wettability of glass powder particles and homogeneous distribution of MG particles in the pastes. Finally, excellent repeatability of the sensor response to the applied deformations was verified in cycling experiments when the sample was submitted to 1000 load/release cycles. These results demonstrated very high stability of the sensor response (within ±1%), and also evidenced high stability of the film under the cyclic strain loads and good film adherence to the substrate.

Firing and Contact Resistivity of Ag<sub>2</sub>O-Aided Pb-Free Silver Paste for Crystalline Silicon Solar Cells

The silver pastes containing Ag2O powder, Ag powder, α-terpineol, ethyl-cellulose and Pb-free glass were synthesized for crystalline silicon (c-Si) solar cells. It was found that α-terpineol assisted the decomposition of Ag2O powder and effectively lowered the decomposition temperature of Ag2O. Ag nanoparticles were produced during the decomposition of Ag2O, which helped to reduce the sintering temperature of the silver pastes. The Ag2O-aided silver pastes were fired on polycrystalline silicon solar cells at various temperatures, and large plate-shaped Ag crystallites appeared at the interfaces between the sintered pastes and the emitter, which ensured a good electrical contact. The contact resistivity of Ag2O-aided silver paste with an optimal ratio of Ag2O to Ag was lower than that of the paste with pure Ag powder. The lowest contact resistivity of Ag2O-aided Pb-free silver pastes sintered at 800°C was 0.029 Ω⋅cm2, which was close to that of commercial silver paste that contained Pb-based glass (0.026 Ω⋅cm2). The experimental data demonstrated that the addition of Ag2O reduced the contact resistance and promoted the sintering of Pb-free silver pastes, and Ag2O-aided Pb-free silver paste could be a promising candidate used for front-contact electrode of c-Si solar cells.

Fabrication of Novel Ag-Paste and Evaluation of its Electrical Properties in Bulk-Si Solar Cell

Two kinds of Ag-pastes were prepared for integrating the bulk Si solar cell. One is the Ag-paste mixed with Pb-based glass frit and the other is that mixed with Pb-free glass frit. The major components in the silver paste were 84 wt% Ag, 2 wt% glass frit, 11 wt% solvent of buthyl-cabitol acetate, and 2 wt% the other additives. After fabricating the Ag-pastes, they were coated on the SiNx/n+/p- stacks of a commercial mono-Si substrate. The solar cell efficiency was 17.6% in case of the silver paste mixed with Pb-based glass frit, which was one of the world-best records in the technology. By the way, the efficiency was 16.2% in the solar cell integrated with the silver paste mixed with Pb-free glass frit. The lower performance in the Pb-free Ag-paste was caused by the higher serial resistance and the lower shunt resistance in comparison with the Pb-containing Ag paste.

Pb-free glass frits prepared by spray pyrolysis as inorganic binders of Al electrodes in Si solar cells

Pb-free glass frits prepared by spray pyrolysis for Al electrodes were of fine size, spherical morphology and dense structure. Their mean size and geometric standard deviation when prepared at 1,200 °C were 1.0 μm and 1.4, respectively. Their glass transition temperature ( T g ) was 374 °C. An Al electrode formed from Al paste with glass frits had a dense structure and good adhesion to the Si substrate. It had a well-developed back-surface field layer of 17.5 μm thickness. Al electrodes formed from Al paste without glass frits had sheet resistances between 21 and 32 mΩ sq −1 as the firing temperature changed from 600 to 900 °C. This compared with values from electrodes formed with frits that decreased from 20 to 7 mΩ sq −1 over the same range of firing temperatures.

무연계 Ag 외부전극재의 열충격에 따른 열화특성과 고장해석

Silver pastes as the outer electrodes have been prepared using Pb-free glass frits with different content of and the effects of glass composition on the degradation behaviors of the Ag electrodes were investigated using the change of adhesion between Ag electrode and alumina substrate with thermal cycle stress. Low adhesion and high surface resistance were observed in Ag electrode using glass frit with a content of 60 wt%, owing to the open microstructure formed at the firing temperature of . When the was increased to 80 wt% in the glass frit, the Ag electrodes had a dense microstructure with high adhesion and a low surface resistance. Delamination of the Ag electrodes was a major failure mode under thermal cycle stress and this was attributed to residual stress due to the thermal expansion mismatch between the Ag electrode and the alumina substrate.

Comparison of Transmittance of Pb-Free Transparent Dielectric Made by Screen Printer and Die Coater

For the application of transparent dielectric layer of PDP (Plasma display panel), a Pb-free glass, ZnO-B2O3-SiO2 glass, was measured for thermal and optical properties after forming thick films. Glass frit of different size (d50=1.7, 4.3㎛) and different thickness film forming process (a die coater and a screen printer) were applied to a transparent dielectric. The coated layer was determined for pore contents, size, and transmittance. As a result, the screen printing method produced non-uniform surface and increased pores with multilayer. The die coater method, however, produced more uniform surface and less pore content compared to the screen printing method. Thus it shows that the increase of pore size and contents has detrimental effects on the transmittance of thick films made by a lead-free glass, ZnO-B2O3-SiO2 glass.

Optical Properties of Bi<sub>2</sub>O<sub>3</sub>-ZnO-SiO<sub>2</sub> Glass System for Eco Transparent Dielectric in PDP

To replace lead oxide glass, Bi2O3-SiO2-ZnO glass, as a Pb-free glass, was examined for optical properties for a transparent dielectric layer of a plasma display panel (PDP). The glass was evaluated for glass transition temperature (Tg) and thermal expansion coefficient (α). The transparent thick films produced with a screen-printing method were evaluated for optical properties. The transmittance of thick films fired at 560-620°C showed above 80%. The results suggest that the bismuth glass is a suitable candidate for one of the lead-free glasses compositions in a transparent dielectric layer.

Effect of RO Components on Some Properties of Pb Free Glass Frit for PDP

The effect of RO components variation on some properties was studied in Pb free glass frit for PDP (Plasma Display Panel). One of the main components, BaO, was replaced progressively at fixed concentration of alkaline earth oxides. We studied the transparency, thermal expansion, softening point, and the high temperature microscopic behaviors of glass frits and TG(thermal gravimetry) of raw material. The compositional dependence of those properties was discussed from the view points of compositional diversity and production process of Pb free glass frit.

Application of Lead-Free Glass to Barrier Rib Materials in Plasma Display Panel

The glass composition, P 2 O 5 -ZnO-BaO-Al 2 O 3 -SiO 2 , was examined as a potential replacement for PbO-based glass frit for plasma display panels (PDP). The composites containing ceramic fillers (Al 2 O 3 and TiO 2 ) were evaluated for Young's modulus (E) and hardness (H) using an indention method with a nanoindenter. The value of elastic modulus and hardness both increased (≃67GPa, 5GPa) as the sintering temperature (540-600 °C) increased. Minimum porosity was obtained at the temperature of 560°C which is near Littleton softening point (Ts) of glass frit. The results suggest that the Pb-free glass frit would be applicable for barrier rib materials in PDP.