STRUCTURAL INVESTIGATION OF MOLTEN AND GLASSY SILICATES BY MEANS OF INFRARED EMISSION SPECTROMETRY

In order to clarify the validity of the dummy role of glassy state instead of molten state, the direct method for observing the molecular vibration in molten state has been developed by means of infrared emission spectrometry. The essential feature of this method consists of a combination of the two emission spectra which are obtained from thin and thick layers of the sample on a metal substratum. Transmission spectrum can be obtained from these emission spectra by virtue of the simple relation reported previously. The infrared emission spectra of molten alkaline silicates were measured in a range of wave number from 25 000 to 400 000 m" and the transmission spectra obtained in molten state were compared with that of glassy state. The obtained results are summarized as follows: (1) The cooling rate from molten to glassy state in the range of 10" to 10* K/s has little influence on the vibrational spectra of the glassy state thus obtained. (2) Although the general pattern of infrared spectra of molten silicates is quite similar to that of glassy state, it is observed that the vibrational frequencies of molten silicates shift toward the lower frequencies and the band shapes are broader than those of glassy state. (3) From the facts that the temperature dependence of these frequency shifts is linear during the transition from molten to glassy state, it may be concluded that the fundamental structure of silicate anion does not differ seriously in both states. 'Present address : Department of Metallurgical Engineering, Toyama University, Takaoka 933, Japan Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1982967 C9-352 JOURNAL DE PHYSIQUE 1. In t roduc t ion . The d i r e c t observat ion o f molten s t a t e i s very impor tant t o c l a r i f y the s i m i l a r i t y o f the s t r u c t u r e between molten and glassy s ta te . Though there are some studies repor ted on the s t r u c t u r e o f molten s i l i c a t e s by means o f X-ray d i f f r a c t i o n [I ,2,3], Raman s c a t t e r i n g [4], and i n f r a r e d r e f 1 ec t ion spectrometry [5,6], i t i s s t i l l necessary fo r b e t t e r understanding o f molten s t a t e t o accumulate more in format ion by o ther kinds o f d i r e c t observat ions. Thus, the d i r e c t method f o r observat ion o f molecular v i b r a t i o n i n molten s t a t e has been developed by means o f i n f r a r e d emission spectrometry. The essent ia l fea tu re of t h i s method cons is ts o f a combination o f the two emission spectra which are obtained from t h i n and t h i c k layers o f a sample on a metal substratum. Transmission spectrum can be der ived r e a d i l y from the combin a t i o n o f these emission spectra by v i r t u e o f a simple r e l a t i o n derived i n previous paper C71. By the a p p l i c a t i o n o f t h i s method t o molten a l k a l i n e s i l i c a t e s , d i s t i n c t v i b r a t i o n a l spectra could be obtained [8]. On the basis o f the experimental r e s u l t s , the general i n t e r p r e t a t i o n o f the s t r u c t u r e o f glassy and molten s i l i c a t e s has been discussed.