A stable and conductive composite material based on NH4PO3 and amorphous oxides (SiO2-P2O5) has been prepared by a wet-chemical route following with firing in ammonia. The composite showed high proton conductivity in both ambient air and humidified 5% H-2/Ar. A total conductivity of 6.0-19 mS/cm in the temperature range of 150-250 degrees C has been achieved. The conductivity (about 19 mS/cm) is stable in humidified 5% H-2/Ar during ageing at 175 degrees C for over 100 h. This material is a potential electrolyte for intermediate temperature fuel cells and other electrochemical devices. (C) 2010 Elsevier B.V. All rights reserved.