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29 Si MAS‐NMR Study of the Short‐Range Order in Potassium Borosilicate Glasses
Author(s) -
Martin Steve W.,
Bhatnagar Ajay,
Parameswar Chitra,
Feller Steve,
MacKenzie Joshua
Publication year - 1995
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1995.tb08421.x
Subject(s) - borosilicate glass , boron , potassium silicate , potassium , oxide , alkali metal , boron oxide , silicon , analytical chemistry (journal) , chemistry , inorganic chemistry , silicate , materials science , nuclear chemistry , mineralogy , organic chemistry
Potassium borosilicate glasses were prepared in families having the general formula of R K 2 O·B 2 O 3 ·NSiO 2 , where R is the ratio of potassium oxide to boron oxide and N is the ratio of silicon dioxide to boron oxide. The glasses were prepared for values of R ranging from 0 to 7.0 in the families N = 0.5, 1.0, 2.0, and 4.0. 29 Si MAS‐NMR measurements were performed on these glasses to determine the short‐range order around the silicon atom. A model of proportional sharing of the added potassium oxide between the silicate and the borate groups was suggested. This model was tested against other suggested models where proportional sharing begins after a minimum amount of potassium oxide, R 0 , and was observed to provide a better fit to the 29 Si chemical shifts obtained. As was observed in the 29 Si MAS‐NMR studies of the R Li 2 O·B 2 O 3 ·NSiO 2 glasses, the proportional sharing model with R 0 = 0 is in stark disagreement with that proposed by the 11 B NMR studies of the alkali borosilicate glasses. This problem is as yet not understood. Since K 2 CO 3 was used as the starting material for K 2 O, it was observed that at large R values, R > R CO2 , where R CO2 = 2.3 for N = 1, R CO2 = 4.0 for N = 2, and R CO2 = 5.0 for N = 4, CO 2 was retained in the melt in the fashion similar to that observed for other high‐alkali borate and silicate glasses. The N = 0.5 family did not exhibit retention at the compositions studied. 29 Si MAS‐NMR could be used to determine where CO 2 retention began in composition and the proportion of K 2 O/K 2 CO 3 in the melt (glass).