Preparation Of Rare-Earth Doped YAG Transparent Ceramics By Using Solid-State Reaction Method And Their Properties

Yttrium aluminum garnet (Y3Al5O12, YAG) is an important ceramic material with promising chemical stability, optical and mechanical properties. It can be used as refractory coating for electronic devices and as the host for rare-earth doped phosphors and for solid state laser. Recently, as an alternative of single crystal YAG, polycrystalline YAG ceramic was given much attention. At present, the synthesis methods of YAG powders include solid reaction, sol-gel processing and precipitation method, among which solid reaction method is widely used for its high yield and simple process. In this dissertation, rare-earth doped transparent YAG ceramics were fabricated by using solid-state reaction method from commercial Y2O3, Al2O3and rare earth oxide powders.Rare-earth doped YAG transparent ceramics of CexY1.5-xGd1.5Al5O12and CexY3-xAl5O12compositions were fabricated from commercial Y2O3, Al2O3, Gd2O3powders and Ce(NO3)3·xH2O. With the increase of Ce3+concentration, the grain size of the sintered ceramics increased whereas the transmittance decreased; when x=0.02, sintered ceramics of CexY1.5-xGd1.5Al5O12and CexY3-xAl5O12had an in-line transmittance of65.24%and76.59%respectively (λ=800nm). The luminous intensity of CexY3-xAl5O12ceramics first increased and then decreased with the increase of Ce3+doped, revealing a maximum at x=0.05. For the CexY1.5-xGd1.5Al5O12ceramics, on the other hand, the luminous intensity decreased with the increase of Ce3+doped. The sample had a maximum luminous intensity at x=0.02. Comparison of CexY1.5-xGd1.5Al5O12and CexY3-xAl5O12, can be found that while doped Gd3+the luminous intensity weakened; Annealing will affect the luminous intensity of the sample, while the excitation and emission wavelength does not changed.Aqueous Yb:YAG suspensions were prepared with PAA-NH4as the dispersing agent, optimum dispersant content is0.5wt%; do not need adjust the pH value, ballmilled for16h is the best; green density increased with rise in solid content; comparison of powder calcined at different temperatures found that1200℃calcined powder have better sintering ability but easier to layer in the molding process,1300℃calcined powder have poor sintering ability, but can form a uniform green body; Comparison of different methods of surface treatment on the powder found that the powder treatmented at50℃by H3PO4have better dispersion properties, could preparated slurry that solid loadings more than40vol%.Use mold pressing process to prepare Yb:YAG/YAG green body with a layered composite structure, vacuum sinterted at different temperature, after1700℃sintered samples have slightly transparency; the grain and pore size with the sintering temperature grow up, Pore is the main reason affecting the sample transparent.