The powder of Li1+x+yScxYyTi2-x-y(PO4)(3) (x=0.15-0.3, y=0.01-0.15) has been synthesized by solid phase reaction. The structure of the compounds was determined by X-ray diffraction patterns from the powder. The compounds belong to the rhombohedral symmetry (space group Me) with Z=6 formula units in the lattice. Ceramic samples were sintered in air at temperature T-s = 1523 K varying sintering time (t(s),) from I to 5 h. The element compositions of ceramics were defined by XPS. The complex impedance ((Z) over tilde), electric conductivity ((sigma) over tilde), dielectric permittivity ((epsilon) over tilde) of the ceramics in frequency range (10(6)-1.2 . 10(9)) Hz and temperature range (300-600) K were carried out. Two relaxation dispersions of the electric parameters were found for all compounds. The dispersions are caused by the ion transport in grains and grain boundaries of the ceramic samples. The values of the bulk (sigma(b)), grain boundaries (sigma(gb)) conductivities, their activation energies, and dielectric permittivity are dependent on stoichiometric parameters x,y and sintering conditions of the ceramics. (c) 2007 Elsevier B.V. All rights reserved.