The Effects of La2O3 on the Sintering Behavior and Dielectric Properties of BaTiO3-Based Ceramic

• Main Authors: Ken-Uei Yeh, 葉耿岳
• Other Authors: Tsang-Tse Fang
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/41668513198842574622

碩士 === 國立成功大學 === 材料科學及工程學系 === 89 === Abstract The principle in present experiment with different La2O3 compositions were doped in BCTZM is discussed for the influence of properties among electrical, sintering behavior and microstructure. It must be asked to con-form to the specification of EIA (Electronic Industry Association), for ex-ample the specification in EIA is for Y5V, Z5U and X7R…etc. The results in our experiment, which match the one of EIA specifications, must be re-quired. In present experiment, the BCTZM is used as a starting powder, which contained the other ions. The other ions are calcium, zirconium and man-ganese ion. It must have a complex influence to the properties of electrical and microstructure in BCTZM with doping La2O3. For manganese ion, which has many different valences, when we doped different ions or con-centration into BCTZM, the valence of manganese will change into 2+, 3+ and 4+. The change in valence of manganese will be influenced by BCTZM with sintering in different atmosphere. From previous results, we can find that BCTZM sintered in 1%H2-99%N2 reduced atmosphere, the resistivity in room temperature is lower about 1~2 order than that sintered in air. But when it sintered in 5% H2-95%N2 reduced atmosphere, the resistivity in room temperature would reduce about 3 orders. From these results, we can explain that sintered in different oxygen partial pressure could produce the free electron. If BCTZM were sintered in much lower oxygen partial pressure than 5% H2-95%N2 atmosphere, the change in valence of manganese was not enough to compensate free electron. For calcium ion in BCTZM, the valence of calcium is fixed that is not like the valence change in manganese to resist reducing atmosphere. From the phase diagram in BaO-CaO-TiO2, we can obtain that calcium ion not only occupy the A-site, but also occupy the B-site, so we can doped La2O3 into BCTZM to cause A/B>1, then some of A-site ions will be replaced and the other ions will be into the B-site. From BaO-CaO-TiO2 phase diagram, we think that the other ions were into B-site is calcium ions. However, we can see a viewpoint from defect chemistry, when the calcium ion occupied the Ti4+-site, it must cause to the net charge not balance. So it would make a like-acceptor type dopant, then it could compensate the free electron that were produced in reducing atmosphere. In final, we can say that the BCTZM with doping La2O3 will be able to resist BCTZM sintered in at-mosphere. BCTZM with La2O3 doped obtained an ability of resisting resistivity reducing and having a higher dielectric constant, lower dielectric loss than undoped BCTZM. It conform completely a Z5U specification in EIA.