Rare-earth doped apatite-type lanthanum silicates, La(5)ASi(6)O(27) (A = Nd, Sm, Gd, Yb), are synthesized by the high-temperature solid state reaction process. The microstructure and electrical properties of La(9)ASi(6)O(27) ceramics are investigated by X-ray diffraction, scanning electron microscopy and complex impedance analysis. La(9)ASi(6)O(27) ceramics are composed of hexagonal apatite-type structure and a very small amount of second phase La2SiO5. The total electrical conductivity of rare-earth doped lanthanum silicates obeys the Arrhenius relation, and gradually increases with increasing temperature from 673 K to 1173 K. Lanthanum silicates doped with Nd or Yb cations exhibit a higher total electrical conductivity than undoped lanthanum silicate. The highest total electrical conductivity value obtained at 773 K is 4.31 x 10(-4) S cm(-1) for La9NdSi6O27. At 1073 K, La9NdSi6O27 and La9YbSi6O27 have a total electrical conductivity of 8.20 x 10(-3) S cm(-1) and 1.03 x 10(-2) S cm(-1), respectively, which are distinctly higher than undoped La10Si6O27 (5.84 x 10(-3) S cm(-1)). However, the situation is reversed when Sm or Gd rare-earth cations are doped into lanthanum silicate. (C) 2012 Elsevier Ltd. All rights reserved.