SYNTHESIS OF AMORPHOUS GeO_2 WITH HIGH DENSITY

本研究旨在合成高密度非晶GeO_2，其局域结构主要由八面体配位的GeO_6组成。第一个实验通过添加乙酰丙酮对异丙醇锗[Ge(OiPr)_4]进行水解。当反应速率控制得当时，有时会发生溶液的脱水收缩，溶液固化成透明凝胶。 X射线粉末衍射的宽晕图表明样品处于无定形状态，并且[Ge(OiPr)_4]被证明是适合制备凝胶的起始材料，尽管反应的重现性不是那么好。为了获得可重现的结果，尝试了第二个实验。将适量的NH_4OH和H_2O加入到预先制备的[Ge(OiPr)_4]和异丙醇的混合物中。将几滴N-N二甲基苯甲胺滴加到上述混合溶液中。干燥后，发生脱水收缩，样品变成透明凝胶。凝胶的 X 射线衍射光晕图案显示样品处于无定形状态。在空气中加热凝胶时，这种状态保持到 500°C。进一步加热超过该温度时，观察到开始结晶为 α-石英型。将起始材料的透明凝胶密封在银管中，并置于高温高压条件下。结晶在150℃以上开始。出现的相的晶体结构取决于压缩的大小。当施加压力低于200MPa时，产生α-石英型。当压力超过此值时，金红石型会结晶。在最终实验中，凝胶在室温下压缩至 200MPa，然后在空气中加热至 500°C。证实凝胶结晶为金红石型相。这一结果表明，在室温下压缩超过200MPa的凝胶的局部结构中包含GeO_6八面体。换句话说，高密度凝胶的合成无需施加非常高的压力。较少的

This research aimed the synthesis of amorphous GeO_2 with high density whose local structure mainly consists of octa-hedrally coordinated GeO_6.In the first experiment, hydroysis of germanium isopropoxide [Ge(OiPr)_4] was undertaken by adding acetylacetone. When the reaction rate was properly cntrolled, it sometimes happened that the syneresis of the solution took place and the solution solidified into transparent gel. A broad halo pattern of X-ray powder diffraction indicated that the sample was in the amorphous state and [Ge(OiPr)_4] was proved as a starting material suitable to prepare gel, although the reproducibility of the reaction was not so excellent.To obtain reproducible result, the second experiment was attemped. Proper amounts of NH_4OH and H_2O were added into the mixture of [Ge(OiPr)_4] and isopropanol prepared in advance. A few drops of N-N dimethylbenzilamine was dripped to the above-stated mixed solution. When dried, the syneresis occurred and the sample turned to tran … More sparent gel. The halo pattern of the X-ray diffraction of the gel showed the sample in an amorphous state. On heating the gel in air, this state was preserved up to 500ﾟC.The commencement of crystallization to alpha-quartz type was observed on further heating beyond this temperature.The transparent gel of starting material was sealed in a Ag tube and submitted to high temperature-pressure conditions. Crystallization began above 150ﾟC.The crystallographic structure of the appeared phase depended on the magnitude of compression. When the applied pressure was lower than 200MPa, alpha-quartz type was produced. In the case when the pressures exceeded this, the rutile type crystallized.In the final experiment, the gel was compressed to 200MPa at RT and then heated at 500ﾟC in air. It was confirmed that the gel crystallized to rutile type phase. This result indicated that the gel compressed beyond 200MPa at RT included GeO_6 octahedra in its local structure. In other words, the high density gel was synthesized without applying very high pressures. Less