以反應燒結法製備價數補償Ba1-xAx(FeTa)0.5O3之
結構與介電性質研究(A=La、Na)

本研究係以反應燒結法在不經煆燒步驟下合成複合型鈣鈦礦陶瓷Ba(FeTa)0.5O3 (BFT) 之主體材料，並以不同價數之La3+、Na+離子來取代Ba2+離子位置，以製備出Ba1-xAx(FeTa)0.5O3 (A=La、Na) (x = 1 ~ 20 mol%) 之複合型鈣鈦礦強介電陶瓷體，探討其結晶、顯微結構特性與介電性質。在Ba(FeTa)0.5O3主體上，由前人文獻參考BFT之成相溫度，在不經煆燒下直接將塊體於1350℃燒結8小時即可得到單一相之BFT鈣鈦礦陶瓷結構，且依不同黏結劑(PVA)之配比，亦產生不同之結果。此外，Ba(FeTa)0.5O3介電陶瓷體在1350℃燒結溫度下由FE-SEM發現，其顆粒大小變化會受不同PVA濃度所影響，PVA濃度愈高則密度越佳、孔隙愈少，且顆粒有成長之趨勢，其介電常數及介電損失在100Hz下，分別為19k與0.279。另外，以反應燒結法合成Ba1-xAx(FeTa)0.5O3 (A=La、Na) (x = 1 ~ 20 mol%) 之複合型鈣鈦礦強介電陶瓷體。由研究顯示，BLFT及BNFT陶瓷分別在1350℃燒結8小時及1300℃燒結8小時可獲得最佳的介電性質。其中Ba0.98La0.02(FeTa)0.5O3陶瓷在頻率100 Hz及溫度0~180℃之介電常數為5×103 ~ 4×105，而Ba0.96Na0.04(FeTa)0.5O3陶瓷體在頻率100 Hz及溫度0~180℃之介電常數為3×105~3×106。且不論BLFT及BNFT摻雜量為多少，其介電值均隨頻率的減少而增加，此表示BLFT及BNFT介電陶瓷為典型強介電弛緩體之介電材料，並在低頻範圍內擁有大量的方向性極化以及空間電荷極化。此外，在燒結過程中由於氧空缺在晶界與晶粒的擴散速度不同，使得晶界之阻抗遠大於晶粒，因而形成所謂的晶界層電容，另外，由於Na+具有較低的熔點，此會使陶瓷體產生液相燒結，令緻密度提升，以上等反應均會提高BLFT及BNFT陶瓷體之介電常數。

關鍵字

反應燒結法；介電材料；複合型鈣鈦礦陶瓷

並列摘要

In this investigation, an complex perovskite structure Ba(FeTa)0.5O3 (BFT) was chosen as the host material and doped with trivalence La3+ ions and divalence Na+ ions which substitute the Ba2+ ion to form Ba1-xAx(FeTa)0.5O3 (A=La, Na) ceramics by reaction sintering. The pure perovskite phase was found in Ba(FeTa)0.5O3 after 8h sintered at 1350℃.The theoretic density increased with PVA increased, and a maximum theoretic density was at PVA 5wt%. The dielectric constant and dielectric loss tangent of Ba(FeTa)0.5O3 at 100 Hz were 19k, 0.279.In addition, in the complex perovskite oxides Ba1-xAx(FeTa)0.5O3(A=La, Na)system, when increasing the La3+ ion concentration, the dielectric constant was decreased owing to the La3+ would made particle growth difficult and produce porosity increased. The dielectric constant is about 1×104¬ at 30 ℃of Ba0.98La0.02(FeTa)0.5O3 ceramic sintered at 1350℃ for 8h, measured at 100 Hz. The grain boundary-layer capacitance was produced for Cole-Cole plot analysis. In addition, when increasing Na+ ion concentration, the density was increased due to the melting point of Na+ is about 851℃, it would made density became earlier. All of samples were over than theoretic density 90%. The dielectric constant is about 8×105 at 30℃ of Ba0.96Na0.04(FeTa)0.5O3 ceramic sintered at 1300℃ for 8h, measured at 100 Hz. The dielectric relaxor behavior with a broad temperature range was obtained for the BLFT and BNFT ceramics which was contributed by orientation and space charge polarization.

並列關鍵字

Reaction-sintering process ； Dielectric property ； Pervoskites

參考文獻

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[11] S. Saha and T. P. Sinha, 2002, "Low-temperature scaling behavior of BaFe0.5Nb0.5O3", Phys. Rev. B: Condens. Matter 65 134103.

[12] 鍾朝宇，2005，"複合型鈣鈦礦Ba1-xAx(Fe0.5Nb0.5)1-x/4O3(A=La、Bi)之介電性質研究"，國立成功大學材料科學及工程博士論文

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以反應燒結法製備價數補償Ba1-xAx(FeTa)0.5O3之結構與介電性質研究(A=La、Na)

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