本研究採用氧化物混合法(Mixed-Oxide),合成Nd2O3-TiO2系統中的介穩態(Metastable)化合物:Nd2Ti3O9-δ(此化合物無法以固態混合法直接合成)。首先分別添加CaO、SrCO3、PbO以及Al2O3與Nd2O3及TiO2做反應,結果均可幫助形成Nd2Ti3O9-δ,但在介電特性上,除了添加Al2O3的頻率溫度係數較佳之外,並無相當理想的結果。 同樣以氧化物混合法合成Nd2(Ti1-xAlx)3O9-δ(x=0.1~0.5),發現燒結溫度隨著Al添加量的增加而上升,而介電常數則隨之下降,Q*f值則有上升的趨勢,而頻率溫度係數(τf)則由正值緩慢下降而至負值(約為+20~-20)。另外在本實驗x=1的成分中,加入微量(0.05mol%)的Mn、Zn、Cu、Fe四種副添加物,並沒有預期改善的結果。本實驗所得到最佳特性條件為:Nd2(Ti0.6Al0.4)3O9-δ,介電常數40.48,Q*f≒10260,共振頻率7.17GHz,τf=-14ppm/℃。
Reactive powders of stoichiometry Nd2Ti3O9-δ are prepared by mixed-oxide method with substitutions Ca, Sr, Pb and Al. The substitution of Nd by Ca, Sr and Pb or substitution of Ti by Al can readily promote the formation of single phase Nd2Ti3O9-δ. However, the better microwave properties are on the substitution of Al. The sintering temperature is increasing with more substitution of Al. But the dielectric conatant is decreasing and the Q*f value is increasing with the increasing of Al. Especially the τf changed form + value to – value. The best properties obtained is derived from the substitutional dopant Al, and the condition is Nd2(Ti0.6Al0.4)3O9-δ, the permittivity=40.48, Q*f=10260(at 7.17GHz) and τf=-14ppm/℃.
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