Microwave dielectric properties of the (1-x)La2/3TiO3-xLaAlO(3) system

Abstract

The microwave dielectric properties of the (1-x)La2/3TiO3-xLaAlO(3) system in which LaAlO3 having epsilon(r) Q . f(0) = 46,000 (at 7 GHz), and tau(f) = -40- -50ppm/degrees C was incorporated with La2/3TiO3 having epsilon(r) greater than or equal to 90 and positive tau(f) was investigated. The (1-x)La2/3TiO3-xLaAlO(3) crystal system was pseudo-cubic in the range 0.1 less than or equal to x less than or equal to 0.7. Its lattice constant increased with increasing a: even though the amount of LaAlO3 containing Al(0.57 Angstrom) ions which are smaller than Ti(0.64 Angstrom) increased. As the amount of LaAlO3 increased from a: = 0.1 to 0.9, the relative dielectric constant (epsilon(r)) decreased from 50 to 23 and the temperature coefficient of the resonant frequency (tau(f)) decreased from +84 to -50. On the other hand, the value of Q . f(0) reached a maximum (148000 at 9.7GHz) at a: = 0.7, where a rapid increase in the peak intensity of XRD occurred, and further increased after prolonged sintering. The microwave dielectric properties of epsilon(r) = 37, Q . f(0) = 47000 GHz (f(0) = 9 GHz), and tau(f) = -2 ppm/degrees C were obtained near 0.6La(2/3)TiO(3)-0.4LaAlO(3) (x = 0.4) composition.