Bokhonov B B, Burleva L P, Whitcomb D R, Sahyun M R
Institute of Solid State Chemistry, Novosibirsk, Russia.
Microsc Res Tech. 1998 Jul 15;42(2):152-72. doi: 10.1002/(SICI)1097-0029(19980715)42:2<152::AID-JEMT10>3.0.CO;2-H.
Silver halide crystals formed during in situ treatment of silver stearate crystals with various halidizing agents are observed by scanning and transmission electron microscopy to form on the lateral edges of the silver carboxylate crystals. The location of the silver halide phase on the crystal edge is dictated by the anisotropic structure of the silver stearate crystal lattice, specifically, the layered structure in which silver ion layers are separated by long-chain hydrocarbon groups. The formation of AgBr on the lateral faces of these crystals is proposed to be typical not only of the formation of silver halide on silver stearate but also for all silver carboxylates of the general formula [AgCnH2(n-1)O2]2 when the crystals of these silver carboxylates have anisotropic, layered structures. The silver bromide/silver carboxylate heterojunction in an in situ system has been clearly observed by transmission electron microscopy. The heterojunction is comprised of a distorted silver carboxylate lattice, which accommodates the misalignment between the AgBr and [Ag(O2CR)]2 crystal lattices. The nature of heterojunction between the AgBr and the silver carboxylate when the AgBr is prepared separately from the preparation of the silver carboxylate differs from the in situ heterojunction. In this case, a layered compound, proposed to have a Ag1-xNaxSt composition, forms between the AgBr and the silver stearate which is a unique feature of this interface. The differences in the structure of interfaces formed between the silver halide and the silver fatty acid complex result in different silver particle morphologies during thermal development of exposed photothermographic films. The developed silver is generally filamentary when the photothermographic material contains silver halide prepared by the in situ exchange reaction between silver carboxylate and a brominating agent. If the photothermographic material is prepared from previously synthesized silver halide crystals, the preformed AgBr route, the developed silver generally crystallizes as dendritic crystals.
通过扫描电子显微镜和透射电子显微镜观察到，在用各种卤化剂对硬脂酸银晶体进行原位处理过程中形成的卤化银晶体，是在羧酸银晶体的侧边缘上形成的。卤化银相在晶体边缘的位置由硬脂酸银晶格的各向异性结构决定，具体来说，是由银离子层被长链烃基隔开的层状结构决定的。这些晶体侧面上溴化银的形成被认为不仅是硬脂酸银上卤化银形成的典型情况，而且对于通式为[AgCnH2(n - 1)O2]2的所有羧酸银来说也是典型的，只要这些羧酸银的晶体具有各向异性的层状结构。通过透射电子显微镜已经清楚地观察到原位体系中的溴化银/羧酸银异质结。该异质结由扭曲的羧酸银晶格组成，它适应了溴化银和[Ag(O2CR)]2晶格之间的错位。当溴化银与羧酸银分开制备时，溴化银与羧酸银之间异质结的性质与原位异质结不同。在这种情况下，在溴化银和硬脂酸银之间形成了一种层状化合物，推测其组成为Ag1 - xNaxSt，这是该界面的一个独特特征。卤化银与银脂肪酸配合物之间形成的界面结构差异，导致在曝光的光热成像胶片热显影过程中银颗粒形态不同。当光热成像材料含有通过羧酸银与溴化剂之间的原位交换反应制备的卤化银时，显影后的银通常呈丝状。如果光热成像材料是由预先合成的卤化银晶体（预制溴化银路线）制备的，显影后的银通常结晶为树枝状晶体。
