Title: Nucleation and Crystallization of NaNbO<sub>3</sub> from Glasses in the Na<sub>2</sub>O‐Nb<sub>2</sub>O<sub>5</sub>‐SiO<sub>2</sub> System
Abstract: Transparent glass‐ceramics, in which the major phase was NaNbO 3 , were obtained by heat treatment of glasses in the Na 2 O‐Nb 2 O 5 ‐SiO 2 system. The structure of the glass and the changes occurring during crystallization as a function of temperature and heating rate were examined by X‐ray diffraction, transmission and replication electron microscopy, density, and other measurements. On heating, a rather abrupt formation of uniformly dispersed particles was observed. In the early stages of crystallization, these particles contained NaNbO 3 as loose, radially grown dendrites of identical crystal orientation which became dense during later stages of crystallization. The particle sizes ranged from 200 to 10,000 A, depending on the SiO 2 content of the glass. Transparency of the crystallized material was dependent on the particle size rather than on the amount of NaNbO 3 formed. The temperature at which crystallization occurred increased with the heating rate whereas the viscosity at crystallization decreased. For a given value of the rate of crystal formation per °C of temperature increase, the product (viscosity) n × (heating rate) was constant. The nucleation and growth phenomena which occurred in these glasses was attributed to microheterogeneities of higher Nb 2 O 5 content which formed part of the glass structure.
Publication Year: 1967
Publication Date: 1967-07-01
Language: en
Type: article
Indexed In: ['crossref']
Access and Citation
Cited By Count: 80
AI Researcher Chatbot
Get quick answers to your questions about the article from our AI researcher chatbot