DIELECTRIC CHARACTERISTICS OF (A1/2(1+).A1/2(3+))TIO3 CERAMICS AT MICROWAVE-FREQUENCIES

We have investigated the dielectric characteristics at microwave frequencies of perovskites with the formula (A1/2(1+).A1/2(3+))TiO3, (where A1+ represents an alkali metal from the lithium to potassium series and A3+ represents a member of the lanthanide series from lanthanum to lutetium). It was found for the first time that in the case of Li1+ substitution at the A1+ site, the larger the ionic radius of the element which substituted at the A3+ site, the higher the dielectric constant was and the greater the negative shift of the temperature coefficient of resonant frequency was. For the (1 - x)(Li1/2(1+).Sm1/2(3+))TiO3-x(Na1/2(1+).Sm1/2(3+))TiO3 system at 3 GHz, high dielectric properties of epsilon(r) = 81, Q = 2050 and tau(f) = + 17ppm/degrees-C were obtained when x = 0.4.