The Dielectric Properties Of CaCu₃Ti₄O₁₂ With Low-loss Dielectrics Doping

With the development of the microelectronic technology, high-dielectric-constant materials play an increasingly important role for the application in microelectronics, especially for the application in dynamic random access memories (DRAM) devices. Recently, much attention has been paid to an unusual material CaCu₃Ti₄O₁₂(CCTO) because of its giant dielectric constant, The current study focus on the origin of the giant dielectric, however, its little high dielectric loss limits application, how to reduce its dielectric loss rarely studied. This thesis through the appropriate low-loss materials doped to reduce dielectric loss.The giant dielectric constant ceramics of CCTO compounds were prepared by traditional solid-state reaction technique. The effect of calcining and sintering temperature in the synthesis process on the phase structures and dielectric properties was discussed. When calcined at 1000℃and sintered at 1060℃, CCTO sample show the best dielectric properties, the relative dielectric constant is 46000 and the dissipation factor is 0.097 at 1KHz in room temperature. With calcining and sintering temperature increasing, the dielectric constant of CCTO reduced and dielectric loss increased.CCTO ceramics were doped with low-loss dielectrics including MgO, CeO₂, LaAlO₃, LaZn_0.5Ti_0.5O₃(LZT) and LaMg_0.5Ti_0.5O₃(LMT). CCTO phase and dielectric properties which changed with the doping concentration of 0.1-5.0 wt% and the sintering temperature of 1060℃, 1080℃and 1100℃were studied. XRD analysis indicated that CeO₂ phase appeared in 5.0 wt% CeO₂ doping CCTO, and LaAlO₃ phase appeared in 3.0 wt% LaAlO₃ doping, showed doping dielectrics didn't react with CCTO. Dielectric properties measurements show MgO and LaAlO₃ have the better dielectric improving capacity. After doped, the high-frequency dielectric properties tend to be better, dielectric constant and loss decrease with the increase of doping concentration. When preparing temperature changes, the dielectric properties changes are in agreement with the pure CCTO generally. CCTO doped with 3.0% MgO and LaAlO₃ when calcined at 1000℃and sintered at 1060℃, had the dielectric constant of 3000 and 2500, lowest dissipation factor of 0.045 and 0.040 respectively. When CCTO samples were doped with CeO₂, its dielectric constant decreases, loss increases. LZT and LMT have not obvious dielectric improving capacity, and its dielectric properties change little.