Formation of heterovalent Zr-substituted solid solutions (up to 7 mol%) for Yb3+ in Na6Yb3(PO4)(5) and LiNa5Yb3(PO4)(5) complex phosphates was studied by ceramic technique at 950 degrees C. Obtained samples were investigated with X-ray powder diffraction, infrared, and impedance spectroscopy. Zr-substituted (7 mol%) Na6Yb3(PO4)(5) has ionic conductivity of 1.6.10(-2) S/cm at 300 degrees C and 4.8.10(-5) S/cm at room temperature. An updated version of phase diagram for ScPO4-Na3PO4-Li3PO4 quasi-ternary system was provided.