微波介電材料Ba2Ti9O20和Ba(Mg1/3Ta2/3)O3之紅外光譜研究

Abstract

我們研究不同氣體熱退火處理、摻雜不同SnO2濃度之Ba2Ti9O20，及摻雜不同Ni濃度、不同製備過程之Ba(Mg1/3Ta2/3)O3的紅外光譜響應，並探討紅外光譜特徵與其微波特性的關連。 首先，我們觀察到(i)氧氣熱退火處理的Ba2Ti9O20樣品結構具有最大的兆赫波段Q×f值、及最小的介電係數，顯示其結構最完整，空缺較少；(ii)摻雜SnO2濃度0.055 mol的Ba2Ti9O20 樣品，其Q×f值最大。但當摻雜SnO2濃度超過0.055 mol時，部分紅外光吸收峰的半高寬變大。Ba2Ti9O20樣品的晶格同調性降低，導致其品質因子也隨之下降。 再者，我們發現Ba(Mg1/3Ta2/3)O3 的Eu(OII)對稱性241 cm-1振動模，貢獻絕大部分的介電係數，此振動模的半高寬與Ba(Mg1/3Ta2/3)O3的品質因子有緊密的關連性。當摻雜不同Ni濃度或不同製備過程之Ba(Mg1/3Ta2/3)O3的品質因子數值降低時，此振動模的半高寬愈大，表示晶格同調性下降(即1:2有序結構逐漸被破壞)。We study the infrared properties of Ba2Ti9O20 dealt with different annealing gas and doped with different content of SnO2 as well as Ba(Mg1/3Ta2/3)O3 with different Ni doping and with different preparation processes. And we discuss the correlation between their infrared characteristics and microwave properties. First, we obtain the following results. (i) TheBa2Ti9O20 annealed with O2 gas has maximum Q×f value and minimum dielectric constant, which represents the sample has more ordered structure and less defect. (ii)The Ba2Ti9O20 doped with 0.055 mol SnO2 has the maximum Q×f factor value. While the content of SnO2 doped with Ba2Ti9O20 exceeds 0.055 mol, the linewidths of several infrared vibration mode of the Ba2Ti9O20 become larger. Due to the descent of the coherency in lattice vibration modes for Ba2Ti9O20 sample, the Q×f value degrades. Moreover, we find that the vibration mode Eu(II) at about 241 cm-1 of the Ba(Mg1/3Ta2/3)O3 has maximum spectral weight of the optical conductivity. And the linewidth of this vibration mode sensitively gauges the Q×f value. When the Q×f value of the Ba(Mg1/3Ta2/3)O3 which is doped with different Ni content or which is dealt with different preparation processes degrades, then the linewidth of this vibration mode increases, which means the coherency of lattice vibration modes degrades (the 1:2 ordering degree degrades).