CRYSTAL-CHEMISTRY AND ELECTRICAL-PROPERTIES OF NA1+XSCNB(PO4)(3) PHASES

Two Nasicon-type phases Na1+xScNb(PO4)(3) have been obtained by solid state reaction: rhombohedral <(R(3)over bar c)> for 0 less than or equ al to x less than or equal to 1 and monoclinic (C2/c) for 1 < x less t han or equal to 2. In spite of the presence of mixed valence niobium ( V/IV for 0 < x < 1 or IV/III for 1 < x < 2), ionic and electronic cond uctivity measurements have shown the pre-eminence of ionic charge carr iers (Na+) with sigma(300 degrees C) approximate to 10(-3) S cm(-1). A t room temperature, reversible electrochemical intercalation of sodium in the NaScNb(PO4)(3) compound has allowed to scan the range 0 less t han or equal to x less than or equal to 2.