Dielectric Characteristics of (A_1/2 ¹⁺·A_1/2 ³⁺)TiO₃ Ceramics at Microwave Frequencies

Abstract

We have investigated the dielectric characteristics at microwave frequencies of perovskites with the formula (A 1/2 1+ ·A 1/2 3+ )TiO 3 , (where A 1+ represents an alkali metal from the lithium to potassium series and A 3+ represents a member of the lanthanide series from lanthanum to lutetium). It was found for the first time that in the case of Li 1+ substitution at the A 1+ site, the larger the ionic radius of the element which substituted at the A 3+ 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 )(Li 1/2 1+ ·Sm 1/2 3+ )TiO 3 - x (Na 1/2 1+ ·Sm 1/2 3+ )TiO 3 system at 3 GHz, high dielectric properties of ε r =81, Q =2050 and τ f =+17ppm/ °C were obtained when x =0.4.