(Sr1-xCax) Nd2Al2O7 (x = 0, 0.1, 0.3, 0.5) ceramics were synthesized by a standard solid state reaction method. Their microwave dielectric properties were investigated together with the structural evolution. X-ray diffraction analysis indicated that Ruddlesden Popper solid solutions with n = 2 were obtained for all the compositions investigated here. Ca-substitution significantly improved the densification behavior which was associated with the variation of epsilon(r). More importantly, with increasing the content of Ca, tau(f) value was generally improved towards near-zero, and the significantly improved Of value was obtained at x = 0.5. The stacking fault and distorted lattice fringe in the ceramics were confirmed by TEM observation, and these defects were deeply concerned with the microwave dielectric loss. The best combination of microwave dielectric characteristics was achieved for the composition of x = 0.5: epsilon(r) = 21.1, Of = 68,200 GHz and tau(f) = -0.5 ppm/degrees C. (C) 2014 Elsevier B.V. All rights reserved.