Neutron-diffraction studies on liquid, glassy, and crystalline Ca0.4K0.6(NO3)1.4Journal Articles
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abstract
The temperature dependence of neutron diffraction by Ca0.4K0.6(NO3)1.4, in the liquid and glassy states, was measured together with the time dependence of the transformation to the crystalline states. The measurements were performed over the range of Q from 0.2 to 5.5 Å−1 (1 Å = 10−10 m) for temperatures between 300 and 573 K. On cooling, a glass was formed with a glass transition temperature of Tg = 335 K; on heating, two crystalline phases formed at 375 ± 5 K with melting points of 425 and 444 K. As the temperature increased the height of the main peak in the diffraction pattern decreased, its position shifted to lower Q, and its width increases. Each of these parameters varies linearly with temperature. The metastability of the system was exemplified by the crystallization process, which did not occur on cooling, but which did occur on first cooling to 300 K and then on heating to 375 K. The time dependence of the growth of the crystalline powder peaks shows that there are two characteristic growth patterns, with each observed peak coming from one of two compounds. We also report on studies of quenched and heat-treated Ca0.4K0.6(NO3)1.4 by thermal analysis and X-ray diffraction.
