Phase composition and conductance are studied in the Na4-2xCaxP2O7 sys
tem (0 less than or equal to x less than or equal to 0.3). A wide rang
e of solid solutions based on Na4P2O7 is found. The conductivity of th
ese solid solutions is of the sodium cationic nature and equals (3.5-4
.5) x 10(-2) S/cm at 500 degrees C, which is higher than that of pure
Na4P2O7 by more than two orders of magnitude. The role of the Ca2+ add
itive is in the formation of sodium vacancies.