(T)he crystal structure and dielectric properties of Pb1-xCax(Yb0.5Nb0.5)(1-x)(Fe0.5Nb0.5)O-3 (x=0, 0.2, 0.4, 0.6, 0.8, 1.0) have been investigated in this paper by X-ray diffraction (XRD), dielectric and Raman spectroscopic measurements. The crystal structure of Pb1-xCax(Yb0.5Nb0.5)(1-x)(Fe0.5Nb0.5)(x)O-3 Changes from the orthorhombic to the pseudocubic phase with local non-uniform distribution of B-site cations at room temperature when x=0.2. With the further increase of x value, the sample exhibits the phase mixture of pseudocubic phase and Ca(Fe1/2Nb1/2)O-3 (CFN). The dielectric constant increases with the increase of x value up to x=0.2 and decreases with the further increase of x value. The sample exhibits typical dielectric relaxor behavior when x=0.2 and 0.4. (c) 2007 Elsevier B.V. All rights reserved.