Surface and Internal Crystallization in Glasses as Determined by Differential Thermal Analysis

Abstract

A differential thermal analysis (DTA) method has been developed that identifies and distinguishes surface and internal (volume) crystallization in glasses. This method is fast, convenient, and requires only a small quantity of sample, ∼500 mg, to identify the dominant crystallization, surface versus internal, in the glass. In this method, either the maximum height of the DTA crystallization peak, (δT”)p, or the ratio T2p/(ΔT)p, where Tp is the temperature at (δT)p and (ΔT)p the peak half width, is plotted as a function of particle size. The composition of the glasses that have been investigated in the present work include (in mol%) 33.3BaO 66.7SiO2 (BS2), 20Na2O‐80TeO2 (NT4), 22.2PbOll.lNb2O5 66.7TeO2 (PNT), 66.7PbO10.0Bi2O3‐23.3Ga2O3 (PBG), and xLi2O(100 ‐ x)SiO2 (lithium silicate, x = 33.3, 35, 37, and 40 mol%). Both (δT)p and T2p/(ΔT)p decrease with increasing particle size when surface crystallization is the dominant mechanism and increase when internal crystallization becomes predominant. The surface and internal crystallization have been identified by crystallizing the glasses at temperatures, as determined by DTA, and then examining the microstructure by scanning electron microscopy. The temperature at the crystallization peak maximum, Tp, shows no dependence on the crystallization mechanism (surface versus internal) and increases with increasing particle size for all the preceding glasses.

Comparative properties of Sr x Ba1−x TiO3 ferroelectric glass–ceramics prepared by powder sintering and melt casting

“…Table 2 lists the percentages of elements measured on the basis of EDX analyses. Ray et al [19] had studied the crystallization behavior of glass using DTA. The results obtained in our work suggested that the nucleation was largely controlled by the surface nucleation, which was consistent with what has been observed by Ray et al [19].…”

“…Ray et al [19] had studied the crystallization behavior of glass using DTA. The results obtained in our work suggested that the nucleation was largely controlled by the surface nucleation, which was consistent with what has been observed by Ray et al [19]. Figure 4a, b show the XRD patterns for BST glassceramics prepared by powder sintering and melt casting, respectively.…”

Development and characterization of 3CaO·P2O5-SiO2-MgO glass-ceramics with different crystallization degree

“…With increasing surface (decreasing particle size), the crystallization temperature decreases, indicating that the crystallization of the diopside phase occurs preferentially at the surface. This crystallization behavior has been studied by Ray et al [18] in the thermal analysis of glasses.…”

Effect of phase separation on crystallization of glasses in the BaO-TiO2-SiO2 system

“…However, in the non-phase-separated samples of x = 9 and 18, the apparent activation energy increased with the decrease of their granular sizes. In this case of surface crystallization, the rate of crystallization normally increases with the decrease of the granular size of the glass, 25) because the large surface area of the small particles enhances surface crystallization due to the increase in the heterogeneous nucleation points at their surfaces. In other words, the surface crystallization is dominant for the small particle sample and the bulk crystallization is dominant for the larger particle sample for the non-phaseseparated glasses.…”