| Lead-free frit is key materials of the plasma display panels (PDP). But the sealing temperature of the bismuth glass is too high. Its coefficient of thermal expansion is too large. The volume resistivity of vanadium phosphorus glass is too low, and its chemical stability is poor. Phosphorus zinc antimony glass will crystallize in application, and its coefficient of thermal expansion is large. Vanadium phosphorus antimony glass can be formed just in nitrogen environment or reducing atmosphere, to control its production quality is difficult.The chemical reaction mechanisms in the materials preparation are still not clear; and the glass can be easily crystallized, its chemical stability is poor. Many factors that affect the performance and application of the glass are lack of research, such as composition, expansion coefficient, density, chemical stability and conductivity mechanism. Glass structure, mathematical models and physical and chemical data are not studied. These lead-free products cannot meet domestic requirements at present.In order to solve these problems, we design and develop a new kind of low melting sealing glass in the V2O5-P2O5-Sb2O3-Bi2O3system (hereinafter referred to as "VPSB glass"). The content of each component is optimized in the glass. Stability production is fulfilled as common process in air. After Sb2O3and Bi2O3are introduced, the sealing temperature can be adjusted, and crystallization can be avoided. The chemical stability and volume resistivity are improved, while the characteristics of low-expansion of vanadium phosphorus glass can be retained.On the basis of experimental results of infrared spectroscopy and X-ray diffraction analysis, the interaction mechanism of the components is discussed, and the possible structure of the glass is proposed:vanadium-oxide polyhedra alternate with [PO4] tetrahedra, and forms a layered-like vanadium phosphate structure; isolated antimony-oxygen bonds and bismuth-oxygen bonds intersperse in the vanadium-oxide polyhedra and [PO4] tetrahedral; bismuth ions and antimony ions can open the phosphorus-oxygen double bonds and the vanadium-oxygen double bonds, exist between layers, and a weak three-dimensional network is constituted. The "mixing effect" of Sb3+and Bi3+can balance the glass structure and enhance the performance of the glass.The effects of the components on the propertis of the glass are carefully investigated. With Sb2O3or P2O5gradually replacing part of V2O5, the thermal expansion coefficient, characteristic temperature, chemical stability, ability to prevent crystallization and volume resistivity of the glass are all improved. No need to add negative thermal expansion material, the thermal expansion coefficient of this sealing glass can meet the requirements of PDP. And the temperature characteristics are good enough, while the density of the glass is only a half of bismuth glass. Among the four components, the improvement contribution of Sb2O3is predominance. The proposed structure of this VPSB glass is successfully applied to explain the abnormal changes of the expansion coefficient, the characteristic temperature, crystallization and chemical stability. This can help to understand the reaction mechanisms of the glass in preparation and application.A mathematical model on the components and properties are established on the basis of additive theory. The mathematical parameters of the model are optimized. The calculated results show a good linear relationship between the components with the expansion coefficient, density and characteristic temperature, and an exponential relationship between the components with the chemical stability and volume resistivity. Compared with the experimental data, it is proved that our optimization calculation is successful. This work can provide the basis for the optimization of the glass compositions and application, and can also provide a reference for the relevant theoretical research.Based on the above research results, the glass compositions are optimized. The optimized963#glass is tested and verified in Changhong's PDP production line, and has also been verified in the process of carbon nanotubes slurry preparation and application. The optimized glass is able to satisfy both different requirements of the application environments. Its integration performance is better than that of foreign products. Its slurrying performance and chemical stability are better than those of the imported bismuth glass. Its reducing resistance characteristic is superior to traditional lead-based sealing glass. It has now volume use in Changhong's PDP production line.
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