Glass-ceramics of the phosphorus containing Na5RSi4O12-type (R = rare earth) Na+-superionic conductors (Narpsio-V) in the systems Na2O-Y2O3-P2O5-SiO2 and Na2O-Sm2O3-P2O5-SiO2 were prepared by crystallization of glasses. The optimum conditions for crystallization are discussed with respect to the conduction properties and the preparation of uncracked glass-ceramic Narpsio-V. Large enhancement of electrical conductivity has been observed in the glass-ceramics by ion implantation of Na+ ions at 100 keV with a flux density of 10(15) ions/cm(2). Upon this implantation the ionic conductivity of the glass-ceramic Na3.9Y0.6P0.3Si2.7O9 and Na3.9Sm0.6P0.3Si2.7O9 at 300 degreesC is drastically increased from 2.01 X 10(-2) to 5.86 X 10(-2) S/cm and from 2.38 X 10(-2) to 7.15 X 10(-2) S/cm, respectively.