[en] A new possibility for the incorporation of molybdenum in sodium zirconium phosphate (NZP) nuclear waste form was examined. The existence of molybdenum containing NZP-type structures was assessed on the basis of crystal chemical principles. New data were deduced for the system Na_1-xZr₂(PO₄)_3-x(MoO₄)_x (0 ≤ x ≤ 1). The stability region for this solid solution having a NZP structure was determined. It was found that molybdenum can be incorporated into NZP-type ceramics without significant changes of the three-dimensional framework structure. (author)