결정구조와 이온 분극률에 따른 (Al,Mg,Ta)O2고용체의 마이크로파 유전상수 특성

Abstract

The calculated and measured dielectric constants of (1-x)(A <TEX>$l_{1}$</TEX>2/ T <TEX>$a_{1}$</TEX>2/) <TEX>$O_2$</TEX>-x(M <TEX>$g_{1}$</TEX>3/ T <TEX>$a_{2}$</TEX>3/) <TEX>$O_2$</TEX> (0<TEX>$\leq$</TEX>x<TEX>$\leq$</TEX>1.0) solid solutions were investigated by variations of ionic polarizability and crystal structure. (A <TEX>$l_{1}$</TEX>2/ T <TEX>$a_{1}$</TEX>2/) <TEX>$O_2$</TEX> and (M <TEX>$g_{1}$</TEX>3/ T <TEX>$a_{2}$</TEX>3/) <TEX>$O_2$</TEX> were orthorhombic and tetragonal trirutile structure, respectively. When (A <TEX>$l_{1}$</TEX>2/ T <TEX>$a_{1}$</TEX>2/) <TEX>$O_2$</TEX> was substituted by (M <TEX>$g_{1}$</TEX>3/ T <TEX>$a_{2}$</TEX>3/) <TEX>$O_2$</TEX>, the phase transformed to tetragonal structure over 60 mole. Because the total ionic radius of [(Mg+2Ta)/3]<TEX>$^{4+}$</TEX> was slightly bigger than one of [(Al+Ta)/2]<TEX>$^{4+}$</TEX>, the lattice parameters increased with an increase of (M <TEX>$g_{1}$</TEX>3/ T <TEX>$a_{2}$</TEX>3/) <TEX>$O_2$</TEX> substitution. The measured dielectric constant increased with an increase of (M <TEX>$g_{1}$</TEX>3/ T <TEX>$a_{2}$</TEX>3/) <TEX>$O_2$</TEX> substitution and coincided with dielectric mixing rule and the calculated dielectric constant with the molecular additivity rule. There were some differences between the measured and the calculated dielectric constant. The reason of the lowered dielectric constant comparing with the calculated one was compressed stress due to the electronic structure of tantalum.