Electrical properties of Li1+xYyTi2−y(PO4)3 (where x, y=0.3; 0.4) ceramics at high frequencies

Ionic conductivity of new rhombohedral compounds of Li1+xYyTi2−y(PO4)3 system (where x, y=0.3; 0.4) has been investigated by impedance spectroscopy in the frequency range from 7×105 to 1.2×109 Hz at temperatures up to 600 K. The method of high frequency investigation of the electric parameters of the disordered materials is presented. The powder samples were synthesized by a solid phase reaction and studied by X-ray diffraction, which revealed changes in interplanar distances with change of x and y. Two relaxational dispersions of the electrical parameters were found and analyzed in terms of bulk and grain boundary ionic transport processes. The highest bulk conductivity σb=0.18 S·m−1 with activation energy ΔEb=0.27 eV at room temperature was found for the compound with x, y=0.4 and these characteristics do not depend on sintering time of samples. The total ionic conductivity increase with number of Li+ ions in the unit cell. The values of total ionic conductivity of the polycrystalline samples depend on time of sintering due to change of grain boundary resistance.