物理化学学报 >> 1987, Vol. 3 >> Issue (03): 292-297.doi: 10.3866/PKU.WHXB19870313

研究论文 上一篇    下一篇

掺杂正八面体AgBr乳剂介电频谱的研究——I-离子的影响

程虎民   

  1. 北京大学物理化学研究所
  • 收稿日期:1986-03-14 修回日期:1986-08-06 发布日期:1987-06-15
  • 通讯作者: 程虎民

STUDY ON THE DIELECTRICSPECTRA OF DOPED OCTAHEDRAL AgBr EMULSIONS——THE EFFECT OF I- IONS

Cheng Humin   

  1. Institute of Physical Chemistry; Peking University
  • Received:1986-03-14 Revised:1986-08-06 Published:1987-06-15
  • Contact: Cheng Humin

摘要: 本文研究了用不同量的I~-(1×10~(-3)-4×10~(-2)mol I~-/mol AgBr)进行表面掺杂的正八面体AgBr乳剂的介电吸收频谱, 并用强X射线光源相应作了多晶X射线物相分析。当I~-的加入量小于1×10~(-2)mol/mol AgBr时, 介电吸收峰随加入I~-量的增加而逐渐向高频方向位移。吸收峰弥散, 分布很宽。当I~-的加入量大于1×10~(-2)mol/mol AgBr时, 样品的介电吸收峰不再明显向高频方向移动, 峰形亦相对比较尖锐。已有证据表明, 在掺杂I~-以后, 在AgBr微晶的表明层内除生成Ag(Br, I)混晶外, 还附生有一薄层β-AgI。分散相颗粒表面层大约2.0 nm范围内的组成与结构对非均匀电介质中的界面极化效应有重要影响, 此外, 对界面极化效应应用的可能性作了初步探讨。

Abstract: The monodispersive octchedral AgBr (0.8 μm) emulsion was prepared by the double-jet method. After doping I~- (1×10~(-3)-4×10~(-2)mol I~-/mol AgBr) on the sur- face of AgBr, the dielectric absorption peak of samples shifted gradually to hi- gher frequencies. When doped I~- content is lower than 1×10~(-2)mol/mol AgBr, the absorption peaks are dispersive. When doped I~- content is≥1×10~-mol/mol AgBr, the absorption peaks are sharper and do not shift markedly to higher frequencies any longer. In the sample with 1×10~(-2) mol I~-/mol AgBr, the strongest X-ray diffraction peak (002) of AgI has been observed. In the sample with 4×10~(-2) moo I~-/mol AgBr, three strongest peaks (100), (002), (110) of the β-AgI have been obsrved. The results of X-ray analysis show that these AgI are chiefly epitaxial on the surface of AgBr by substitution. On the average, 1 mol% I~- can substitute about five layers Br~- ions on (111) surface of AgBr (0.8 μm).
From the above experimental results, it may be considered that the thickness of the surface layer which influence on the interfacial polarization is about 0.2 nm. In this thickness range, if I~- distribution is heterogeneous, the dielectric absorption peak of sample will be getting dispersive.