Ba(Zn1/3Nb2/3)O-3 (BZN)-CaTiO3 (CT) microwave dielectric ceramics were synthesized at 1395 degrees C for 4h using conventional solid-state sintering technique with different CT contents. The ceramics were characterized by X-ray diffraction (XRD) and far-infrared reflection (FIR) spectroscopy to evaluate correlations among crystal structures, dielectric properties, and infrared modes. XRD results showed that crystal symmetry decreased with increased CT concentration from cubic to hexagonal structure, and lattice constants and ordered degree changed accordingly. Ordered phases transformed from 1:1 to 1:2 ordered structure with crystal-structure change. FIR results demonstrated that two new IR active modes appeared at 300 cm(-1), and another new mode appeared at 600 cm(-1) for the x >= 0.60 sample, which agreed with the change in crystal structures as confirmed by XRD results. Correlations between FIR modes and dielectric properties were established. (C) 2015 Elsevier Ltd. All rights reserved.