Phase Relation and  Microwave Dielectric Properties of <TEX>$BaO-(Nd, Sm)_2O_3-TiO_2$</TEX> Ceramic System

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J. Korean Ceram. Soc. > Volume 31(9); 1994 > Article

Journal of the Korean Ceramic Society 1994;31(9): 995.

$BaO-(Nd, Sm)_2O_3-TiO_2$계 세라믹스의 상관계 및 마이크로파 유전특성

김희도, 김진호, 조상희

경북대학교 공과대학 무기재료공학과

Phase Relation and Microwave Dielectric Properties of $BaO-(Nd, Sm)_2O_3-TiO_2$ Ceramic System

ABSTRACT

Phase relation and microwave dielectric properties of the system BaO.(Nd1-xSmx)2O3.TiO2 (n=4, 5) were studied. With n=5 (1 : 1 : 5), Ba2Ti9O20 and TiO2 formed in case of X$leq$0.7, and Ba2Ti9O20 and Sm2Ti2O7 formed at X=1.0 as the second phases dispersed in fine-grained orthorhombic matrix phase. With n=4 (1 : 1 : 4). on the contrary, only fine grains of an ortho-rhombic phase were observed irrespective of Nd/Sm ratio. The compositions of these two stable orthorombic phases having distinct lattic constants even with the same Nd/Sm ratio were estimated as 4BaO.5(Nd1-xSmx)2O3.18TiO2 and BaO.(Nd1-xSmx)2O3.4TiO2 with n=5 and n=4 in the system BaO.(Nd1-xSmx)2O3.TiO2, respectively. Consequently the composition BaO.(Nd1-xSmx)2O3.5TiO2 lies in the compatible triangle of 4BaO.5(Nd1-xSmx)2O3.18TiO2 and the second phases mentioned above. The microwave dielectric properties (~4 GHz) of BaO.(Nd1-xSmx)2O3.5TiO2 can be controlled effectively by adjusting Sm content : with increasing X from 0 to 0.7, both dielectric constant and the temperature coefficient of resonant frequency decreased monotonically from 82 to 65 and from 91 (ppm/$^{circ}C$) to -19(ppm/$^{circ}C$), respectively, while unloaded Q(Qo) remained constant at about 2,600.