Crystallographic structures of two new orthophosphates Ca_0.50SbFe(PO₄)₃ and CaSb_0.50Fe_1.50(PO₄)₃ obtained by conventional solid state reaction techniques at 900 °C, were determined at room temperature from X-ray powder diffraction using Rietveld analysis. The two compounds belong to the Nasicon structural family. The space group is R3 for Ca_0.50SbFe(PO₄)₃ and R3c for CaSb_0.50Fe_1.50(PO₄)₃. Hexagonal cell parameters for Ca_0.50SbFe(PO₄)₃ and CaSb_0.50Fe_1.50(PO₄)₃ are: a=8.257(1) Å, c=22.276(2) Å, and a=8.514(1) Å, c=21.871(2) Å, respectively. Ca²⁺ and vacancies in {[Ca_0.50]_3a[◻_0.50]_3b}_M1SbFe(PO₄)₃ are ordered within the two positions, 3a and 3b, of M1 sites. Structure refinements show also a quasi-ordered distribution of Sb⁵⁺ and Fe³⁺ ions within the Nasicon framework. Thus, in {[Ca_0.50]_3a[◻_0.50]_3b}_M1SbFe(PO₄)₃, each Ca_(3a)O₆ octahedron shares two faces with two Fe³⁺O₆ octahedra and each vacancy (◻_(3b)O₆) site is located between two Sb⁵⁺O₆ octahedra. In [Ca]_M1Sb_0.50Fe_1.50(PO₄)₃ compound (R3c space group), all M1 sites are occupied by Ca²⁺ and the Sb⁵⁺ and Fe³⁺ ions are randomly distributed within the Nasicon framework.