臺灣博碩士論文加值系統

鈣添加之鈦酸鋇陶瓷目前為商業上常用之卑金屬內電極的積層陶瓷電容器
且其規格是符合EIA Y5V 的粉末, 其在抵抗還原氣氛能力的機構有缺陷化
學(CaTi),214相與六方晶相,且鈣欲佔據鈦位置的先決條件為(Ba+Ca)/
Ti>1,故本實驗的主要目的在於(1)探討鈣添加鈦酸鋇在還原氣氛中不會半
導化的機構(2)為何(Ba+Ca)/Ti>1是鈣離子佔據鈦離子位置的先決條件.由
本實驗結果得知,介電常數與溫度的關係曲線得知,傳統製程無論是否先經
粉末鍛燒步驟,其Tmax均有明顯往低溫偏移,至於半濕式製程如先經粉末鍛
燒步驟,其Tmax並無明顯往低溫偏移,但如未經粉末鍛燒而直接壓形燒結,
其Tmax有明顯往低溫偏移但偏移程度約與製程c接近.燒結氣氛對於同一製
程且同組成之試片的Tmax並無明顯影響,反而是m值對於介電行為的Tmax有
明顯影響.從X光粉末繞射及室溫絕緣電阻與m值的關係圖可知,六方晶相
及214相對於室溫絕緣電阻並無明顯影響,反而是含鈣離子的鈦酸鋇固溶體
相在m>1時對於室溫絕緣電阻有顯著影響.從statistical ALCHEMI分析得
知,在m>1時,會有一部份的鈣離子佔據鈦位置,故可歸納出鈣添加鈦酸鋇抵
抗還原氣氛的機構為缺陷化學(CaTi).在m>1時鈣離子會有少量佔據鈦位置
的可能機構為在傳統製程粉末中,起始粉末組成碳酸鋇.碳酸鈣及二氧化鈦
會先形成鈦酸鋇.鈦酸鈣及碳酸鋇,當溫度升高時鈦酸鈣及碳酸鈣欲擴散入
鈦酸鋇形成單相粉末時,因如A超過100ppm會形成214相,碳酸鋇之鋇離子進
入鈦酸鋇晶格中傾向於佔據鋇位置而鈣離子因與鈦離子及鋇離子的離子半
徑相近,故有機會同時佔據鋇離子位置及鈦位置等因素的限制,所以鈦酸鈣
的鈣離子進入鈦酸鋇時,會有部份的鈣離子去佔據鈦位置,導致缺陷(CaTi)
生成

The Ca-doped BaTiO3 ceramics are the raw materials of the
commercial multilayerceramic capacitors with nickel inner
electrodes.The mechanisms of the inhibitionof reduction are the
defect mechanism(CaTi),the 214 phase and the hexagonal phase.The
major factor of the Ti-site occupied by the Ca2+ is that (Ba+
Ca)/Ti>1.The purpose of this study is to (1)discuss the
mechanism of non-semiconductor of theCa-doped BaTiO3
ceramics,(2)why (Ba+Ca)/Ti>1 is the major factor causing the Ti-
siteoccupied by the calcium ions.According to the relation of
the dielectric constant to the temperature,the curie point of
the conventional processed samples,whether via powder
calcination or not,shift to the low teperature.The curie point
of the semiwet processed sample with powder calcination do not
shift obviously,but that without powder calcination shifts as
the same as the conventional process samplewith the powder
calcination.The sintering atmosphere has no effect on the curie
temperature for the same process and the same composition
samples.According to the x-ray powder diffraction and the
resistivity at the room temperature as a function of the ratio
m,the hexagonal phase and the 214 phase has no effect on the
resistivity at the room temperature,but when the ratio m>1,the
Ca-doped BaTiO3solid solution has the significant effect on the
resistivity.According to the statistical ALCHEMI analysis,when
m>1,there are some calcium ion to occupy the Ti-site,so the
mechanism for the Ca-doped to resist the attack of the reducing
atmosphere from becoming semiconductors is the defect chemistry
mechanism(CaTi).When the ratio m>1 and in the convention process
powders,BaCO3,CaCO3 and TiO2 powders will first react to form
BaTiO3 and CaTiO3 and the residual BaCO3,then when the
temperature increases continuously and when CaTiO3 and BaCO3
would like to diffuse into BaTiO3 to form a single phase,because
the effect of that the ABO3would become A2BO4 phase when (A-B)/
B>100ppm,that the barium ions in the BaCO3 powder like to occupy
the Ti-site when diffusing into BaTiO3 lattice,and that the
radius difference between the Ca and the Ti is near to the one
between the Caand the Ba ions,there are some calcium ions
occupying the Ti-site and it leads to the formation of the
defect CaTi,when the Ca ions in the CaTiO3 diffuse into the
BaTiO3 lattice.