New LANTIOX high-temperature conductors with the pyrochlore structure, (Ln(1-x)A(x))(2)Ti2O7-delta (Ln = Dy, Ho, Yb; A = Ca, Mg, Zn; x = 0, 0.01, 0.02, 0.04, 0.07, 0.1), have been prepared at 1400-1600 degrees C using mechanical activation, co-precipitation and solid-state reactions. Acceptor doping in the lanthanide sublattice of Ln(2)Ti(2)O(7) (Ln = Dy, Ho, Yb) with Ca2+, Mg2+ and Zn2+ increases the conductivity of the titanates except in the (Ho1-xCax)(2)Ti2O7-delta System, where the conductivity decreases slightly at low doping levels, x= 0.01-0.02. The highest conductivity in the (Ln(1-x)A(x))(2)Ti2O7-delta (Ln = Dy, Ho, Yb; A = Ca, Mg, Zn) systems is offered by the (Ln(0.9)A(0.1))(2)Ti2O7-delta, and attains maximum value for (Yb0.9Ca0.1)(2)Ti2O6.9 and (Yb0.9Mg0.1)(2)Ti2O6.9 solid solutions:similar to 2 x 10(-2) and 9 x 10(-3) S cm(-1) at 750 degrees C, respectively. Ca and Mg are best dopants for Ln(2)Ti(2)O(7) (Ln = Dy, Ho, Yb) pyrochlores. Using impedance spectroscopy data, we have determined the activation energies for bulk and grain-boundary conduction in most of the (Ln(1-x)A(x))(2)Ti2O7-delta (Ln = Dy, Ho: A = Ca, Mg, Zn) materials. The values obtained, 0.7-1.05 and 1-1.4 eV, respectively, are typical of oxygen ion conductors. We have also evaluated defect formation energies in the systems studied. (C) 2009 Elsevier Ltd. All rights reserved.