Microwave dielectric properties of the [(Pb0.2Ca0.8)(1-x)Sr-x](Ca1/3Nb2/3)O-3 (PCSCN) have been investigated as a function of Sr2+ content (0.05 less than or equal to x less than or equal to 0.2). A perovskite single phase with the CaTiO3-type structure was obtained throughout the entire composition range. Dielectric constant (K) increased with increase of Sr2+ content, however, the quality factor (Qf) was decreased. The increase of dielectric constant (K) could be attributed to the increase of ionic polarizability and the decrease of A-site bond valence of the specimens. Temperature coefficient of resonant frequency (TCF) increased with Sr2+ content from -22.26 to -9.15 ppm/degreesC, which could be explained by the change of bond valence and tolerance factor (t) of the perovskite structure. (C) 2002 Elsevier Science B.V. All rights reserved.