The effects of small amounts of Zr substitution for Ti in the low loss, low temperature coefficient dielectric material Ca5Nb2TiO12 are reported. Substitutions at the 1-5% level significantly increase the range of possible firing temperatures at which polycrystalline ceramics with low temperature coefficients can be obtained. This low temperature coefficient state is at the borderline between ordered and disordered states of the Ca, Nb, and Ti ions in the B sites of the perovskite lattice. The kinetics for ordering is apparently enhanced by the Zr substitutions. (C) 2000 Elsevier Science Ltd.