Microwave Dielectric Properties of the (1-x)La2/3TiO3–xLaAlO3System

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The microwave dielectric properties of the (1-x)La2/3TiO3–xLaAlO3system in which LaAlO3havingεr=22,Q·f0=46,000 (at 7 GHz), and τf=-40–-50 ppm/° C was incorporated with La2/3TiO3havingεr≥90 and positive τfwas investigated. The (1-x)La2/3TiO3–xLaAlO3crystal system was pseudo-cubic in the range 0.1≤x≤0.7. Its lattice constant increased with increasingxeven though the amount of LaAlO3containing Al(0.57 Å) ions which are smaller than Ti(0.64 Å) increased. As the amount of LaAlO3increased fromx=0.1 to 0.9, the relative dielectric constant (εr) decreased from 50 to 23 and the temperature coefficient of the resonant frequency (τf) decreased from +84 to -50. On the other hand, the value ofQ·f0reached a maximum (148000 at 9.7 GHz) atx=0.7, where a rapid increase in the peak intensity of XRD occurred, and further increased after prolonged sintering. The microwave dielectric properties ofεr=37,Q·f0=47000 GHz (f0=9 GHz), and τf=-2 ppm/° C were obtained near 0.6La2/3TiO3–0.4LaAlO3(x=0.4) composition.