Deep level donor's ionization behavior of passive film formed on the surface of stainless steel was investigated by Mott-Schottky plots.It is indicated that transformation process of deep level donors' ionization behavior of passive film on surface of stainless steel can be divided into 4 stages with rising immersion time.At the initial immersion stage(10 min),Fe(Ⅱ) located in the octahedral sites of the unit cell is not ionized and the deep level does not appear in Mott-Schottky plots.At the second stage(9-38 h),Fe(Ⅱ) located in the octahedral sites starts to be ionized,which results in deep level donors' generation and density of deep level donors almost is constant with augmenting immersion time but the thickness of space charge layer is more and more thicker with rising immersion time.At the third stage(48 h-12 d),density of deep level donors rises with increasing immersion time and the thickness of passive films space charge layer decreases.At last stage(above 23 d),both the space charge layer's thickness and density of deep level donors are no longer changed with increasing immersion time.In the overall immersion stage,the shallow level donors' density is invariable all the time.The mechanism of deep level donor's ionization can be the generation of metal vacancies,which results in crystal lattice's aberration and the aberration energy urges the ionization of Fe(Ⅱ) in octahedral sites.
采用电位-电容法及Mott-Schottky分析技术研究了有机清漆在5%氢氧化钠溶液中的半导体导电行为。研究表明,有机清漆空间电荷层电容(Capacitance of space charge layer,C_(sc))远小于裸露碳钢电极,随着浸泡时间的延长,其C_(sc)逐渐增大,其空间电荷层逐渐减小。有机清漆在5%氢氧化钠溶液中呈现不同类型的半导体导电特征,环氧清漆膜呈绝缘体,而酚醛和醇酸清漆膜则表现为双极膜特征,在电位(—0.3～0 V)范围呈p型半导体,在电位(0～0.4 V)范围呈n型半导体,且随着浸泡时间的延长,漆膜中载流子浓度逐渐增加。
