Researching For Densification Behavior Of Doped Transparent Alumina Ceramic Substrate

Nowadays, with the rapid development of electronic technology, semiconductor lighting has been attracting more and more attention. LED is a new and efficient light source for energy conservation and environment protection. Making the LED into the shape of an incandescent lamp, a plurality of LED chips in series is an effective measure to increase power. The materials of LED wick carrier substrate require high thermal conductivity, in favor of heat loss from LED bulbs; and good light transmission properties for full use of energy, and reducing the conversion of light energy to heat energy, in order to improve service life. As low production cost, good thermal conductivity, and good light transmission properties, polycrystalline alumina transparent ceramics is a potential substrate material for LED lights. The purpose of this study is to prepare transparent alumina substrates. To study the densification behavior of polycrystalline alumina ceramic, the method is that adding sintering aids to aluminum,changing the sintering process and using tape-casting. Results were as follows:?1? Influence of one additives on the densification of alumina ceramic:MgO-doped Al₂O₃ ceramics: sintered at 1550 ?for 4 hours with pressureless, the grains are smaller than the grain of free added. When the content of Mg O is 0.4wt%, the relative density is highest. Vacuum sintered at 1850 ? for 8 hours, when the content of Mg O is 0.2wt% 0.6wt%, the sample achieve fully densified, with nonporous, clean and modest grain boundaries, and good translucent.SiO₂-doped Al₂O₃ ceramic: sintered with pressureless, the grains are. When content of Si O₂ is 0.1wt%, the relative density is highest.La₂O₃-doped Al₂O₃ ceramic: sintered with pressureless, when the content of La₂O₃ is0.5wt%,the relative density is highest. If the content exceeds 1.0wt%, second phase would be generated.Y₂O₃-doped Al₂O₃ ceramic: sintered with pressureless, when the content of Y₂O₃ is0.75wt%,there are no closed pores with highest relative density. Second phase called YAG at the grain boundaries is produced as the content exceeds 0.75wt%.Adding SiO₂, La₂O₃, or Y₂O₃, and vacuum sintering at 1850 ? for 8 hours, therelative density higher, the grain big, the grain boundary coarse thick, the presence of closed pores inside the grain, result in poor optical property.?2? Influence of composite additives on the densification of alumina ceramic:0.4wt% MgO + 0.1wt% SiO₂, The relative density is 98.556% with low porosity sintering at 1550 ?for 4 hours with pressureless, while the relative density is 99.059%vacuum sintering at 1850 ? for 8 hours, with a small amount of the presence of pores,clean and modest grain boundaries, and slightly translucent.0.4wt% MgO + 0.5wt% La₂O₃, sintered at 1550 ?for 4 hours with pressureless, the relative density is 98.292% and the grain size is homogeneous.Vacuum sintering at1850 ? for 8 hours, the grain is smaller than grain without adding. For no clear pores,clean and modest grain boundary,high relative density, the optical property is wonderful.0.4wt% MgO + 0.75wt% Y₂O₃, sintered at 1550 ?for 4 hours with pressureless, the relative density is 98.397% with low porosity. After vacuum sintering at 1850 ? for 8hours, the grain is much bigger than grain without adding, the grain boundary is thick,and there are a small amount of pores. The sample is slightly translucent.?3? Influence of sintering on the densification of alumina ceramic: the sintering temperature is raised from 1800 ? to 1850 ?, the sample becomes translucent. The optical performance greatly improve. While the holding time of 8 hours, The sample is preferably translucent, as grain size is uniform, and relative density is highest.?4? Producing MgO-doped Al₂O₃ film by tape casting, and vacuum sintering at 1850 ?for 8 hours. With the increase of content, the grain becomes smaller, reducing the pores.When the MgO content is 0.6wt%, the light transmittance in the visible reaches 70%.