Dielectric Characteristics of (A1/2 1+·A1/2 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⁺)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)(Li_1/2 ¹⁺·Sm_1/2 ³⁺)TiO₃-x(Na_1/2 ¹⁺·Sm_1/2 ³⁺)TiO₃ system at 3 GHz, high dielectric properties of ε_r=81, Q=2050 and τ_f=+17ppm/ °C were obtained when x=0.4.