Two newly synthesised Sr0.50SbFe(PO4)(3) [Sr-0.5 center dot] and SrSb0.50Fe1.50(PO4)(3) [Sr.] phases were obtained by conventional solid-state reaction techniques at 1000 degrees C in air atmosphere. Their crystallographic structures were determined at room temperature from X-ray powder diffraction (XRPD) data using the Rietveld analysis. Both compounds belong to the Nasicon structural family. [Sr0.5.] and [Sr.] crystallise in rhombohedral system with R (3) over bar and R (3) over barc space group, respectively. Hexagonal cell parameters for [Sr-0.5 center dot] and [Sr center dot] are: a = 8.227(1) angstrom, c = 22.767(2) angstrom and a = 8.339(1) angstrom, c = 22.704(2) angstrom, respectively. Sr2+ and vacancies in {[Sr-0.50](3a)[square(0.50)](3b)}(M1)SbFe(PO4)(3) are practically ordered within the two positions, 3a and 3b, of M1 sites. Structure refinements show also an ordered distribution of Sb5+ and Fe3+ ions within the Nasicon framework. Within the structure, each Sr(3a)O6 octahedron shares two faces with two Fe3+O6 octahedra and each vacancy (square O-(3b)(6)) site is located between two Sb5+O6 octahedra. In [Sr](M1)Sb0.50Fe1.50(PO4)(3) compound, all M1 sites are occupied by Sr2+ and the Sb5+ and Fe3+ ions are randomly distributed within the Nasicon framework. A Raman and infrared spectroscopic study was used to obtain further structural information about the nature of bonding in both selected compositions.