Analysis on volume fraction and crystal orientation relationship of monoclinic and tetragonal oxide grown on Zr–2.5Nb alloy

Texture and phase volume fraction of the oxide grown on Zr–2.5Nb, in static autoclaves, at 623 K, with lithiated heavy water were investigated. It is found that both monoclinic and tetragonal zirconia are highly textured with {1 0 0}〈1 0 0〉 preferred crystal orientation for the tetragonal phase, and ( 1 0 3 ¯ ) [ 0 1 ¯ 0 ] and ( 1 0 4 ¯ ) [ 4 0 1 ] texture for the monoclinic phase. No change in the texture for both phases was observed with the increase of thickness of the oxide layer. The crystal orientation relationship of both the monoclinic and tetragonal phases was found to be ( 1 0 3 ¯ ) m ‖ ( 1 0 0 ) t or ( 1 0 3 ¯ ) m ‖ ( 1 0 1 ) t and [ 1 0 0 ] t ‖ [ 0 1 0 ] m . The integrated intensity over pole figures was used to calculate the volume fraction of the tetragonal phase in the oxide layer. The volume fraction of the tetragonal phase in the dense oxide layer near the metal–oxide interface was found to be about 8% and gradually decreases with an increase of the oxide thickness.