The sintering behavior, microstructure and microwave dielectric properties of complex pyrophosphate compounds AMP(2)O(7) (A = Ca, Sr; M = Zn, Cu) were investigated in this paper. All compounds could be densified below the temperature of 950 degrees C without any glass addition, and exhibit low permittivity (epsilon(r) < 8), high Q x f value and negative temperature coefficient of resonant frequency. The Q x f value was discussed from the point of view of bond strength. The chemical compatibility with silver and copper was also investigated. All compounds seriously react with silver at similar to 700 degrees C. However SrZnP2O7 could be co-fired with copper in reduced atmosphere, The microwave dielectric properties of SrZnP2O7 sintered at 950 degrees C in reducing atmosphere are: epsilon(r) = 7.06, Q x f = 52781 GHz, tau(f) = -70 ppm/degrees C. In terms of its lower sintering temperature, chemical compatibility with copper and good microwave dielectric properties, SrZnP2O7 ceramic is very promising for low temperature co-fired ceramic (LTCC) applications. (C) 2005 Elsevier Ltd. All rights reserved.