The progress in wireless communications and information access has demanded the use of electronic ceramics exhibiting desired properties. To further our understanding of these properties, compounds in the Ln(2)Ti(2-2x)M(2x)O(7) (Ln = Gd, Er; M = Zr, Sn, Si) systems were synthesized by ceramic methods and characterized by powder X-ray diffraction. The ZrO(2)-doped Gd(2)Ti(2-2x)Zr(2x)O(7) compounds adopt the pyrochlore structure type and form a complete solid solution. Er(2)Ti(2-2x)Zr(2x)O(7) forms a pyrochlore solid solution for x < 0.1. However, stoichiometric Er(2)Zr(2)O(7) does not form; instead Er(4)Zr(3)O(12) forms a with defect fluorite structure. The Sn-doped Ln(2)Ti(2-2x)Sn(2x)O(7) (Ln = Gd, Er) compounds form complete solid solutions, and the Si compounds adopt the pyrochlore structure up to x = 0.05. At ambient temperature, dielectric constants range from 10 to 61 for Er(2)Ti(2-2x)Zr(2x)O(7) and 16-31 for Gd(2)Ti(2-2x)Zr(2x)O(7) with low dielectric loss (I X 10(-3)) at 1 GHz. (C) 2002 Elsevier Science Ltd. All rights reserved.