Surface crystallization tendency of Na2FeP2O7 glass

Crystallization behavior of bulk Na2FeP2O7 glass produced by a melt-quenching method was examined. The valence state of iron is 76% Fe2+ in glass matrix by using Fe(II)O and carbon crucible during glass melting. After mirror polishing crystallization was performed. Surface crystallization of triclinic Na2FeP2O7 was confirmed by heat-treatment of the bulk sample in a nitrogen atmosphere. The outermost surface of crystallized sample have no crystal orientation but, strong (122) and (133) orientation was confirmed by X-ray diffraction of surface crystalized glass obtained after polish 10 µm thick. This technique may be effective to control ionic conductive channel in phosphate derived active material for secondary batteries.