Highly conducting divalent Mg super(2+) cation solid electrolytes with well-ordered three-dimensional network structure

A three-dimensionally well-ordered NASICON-type Mg super(2+) cation conductor, (Mg sub(x)Hf sub(1-x)) sub(4/(4-2x))Nb (PO sub(4)) sub(3), was firstly developed by partial substitution of lower valent Mg super(2+) cation onto the Hf super(4+) sites in a HfNb(PO sub(4)) sub(3) solid to realize high Mg super(2+) cation conductivity even at moderate temperatures. Due to the formation of well-ordered NASICON-type structure, both the high Mg super(2+) cation conductivity below 450 degree C and the low activation energy for Mg super(2+) cation migration was successfully realized for the (Mg sub(0.1)Hf sub(0.9)) sub(4/3.8)Nb(PO sub(4) ) sub(3) solid. Pure Mg super(2+) cation conduction in the NASICON-type (Mg sub(0.1)Hf sub(0.9)) sub(4/3.8)Nb(PO sub(4) ) sub(3) solid was directly and quantitatively demonstrated by means of two kinds of dc electrolysis. Image of the Mg super(2+) cation conduction in NASICON-type (Mg sub(0.1)Hf sub(0.9)) sub(4/3.8)Nb(PO sub(4) ) sub(3) and its Mg super(2+) conductivity.