Sintering and crystallization behavior of CaMgSi2O6–NaFeSi2O6 based glass-ceramics

Abstract

We report on the synthesis, sintering, and crystallization behaviors of a glass with a composition corresponding to 90 mol % CaMgSi 2 O 6 − 10 mol % NaFeSi 2 O 6 . The investigated glass composition crystallized superficially immediately after casting of the melt and needs a high cooling rate ͑rapid quenching͒ in order to produce an amorphous glass. Differential thermal analysis and hot-stage microscopy were employed to investigate the glass forming ability, sintering behavior, relative nucleation rate, and crystallization behavior of the glass composition. The crystalline phase assemblage in the glass-ceramics was studied under nonisothermal heating conditions in the temperature range of 850-950°C in both air and N 2 atmosphere. X-ray diffraction studies adjoined with the Rietveld-reference intensity ratio method were employed to quantify the amount of crystalline phases, while electron microscopy was used to shed some light on the microstructure of the resultant glass-ceramics. Well sintered glass-ceramics with diopside as the primary crystalline phase were obtained where the amount of diopside varied with the heating conditions.

Sintering behavior and devitrification kinetics of iron containing clinopyroxene based magnetic glass-ceramics

“…For all the investigated compositions, except composition 1 [11] ( Table 1), heating at 1580°C for 1 h was adequate to obtain bubblefree, homogenous transparent glasses. The introduction of P 2 O 5 and B 2 O 3 in the parent glass composition (composition 1) enhanced its glass forming ability, thus leading to the formation of a completely amorphous glass as was confirmed by XRD and SEM analyses.…”

“…A side-view hot-stage microscope (HSM) EM 201 equipped with image analysis system and electrical furnace 1750/ 15 Leica was used. A detailed description about the HSM equipment has been described in our previous paper [11]. The measurements were conducted in air with a heating rate of 5 K min − 1 .…”

“…Table 3 presents the sequence of evolution of crystalline phases in the resultant glass-ceramics along with the quantitative analysis of their crystalline and amorphous content as calculated from Rietveld-RIR analysis. The stoichiometric diopside (CaMgSi 2 O 6 ; ICDD: 78-1390) crystallized as the primary phase in glass-ceramic 1 along with minor amount of low quartz (SiO 2 ; ICDD: 89-1961) [11] while introduction of minor amounts of B 2 O 3 and P 2 O 5 (Table 1) Fig. 6 shows the fit of a measured XRD pattern of glass-ceramic 2 by using the GSAS-EXPGUI software.…”

“…In our previous study [11] an attempt was made to prepare a glass with composition Ca 0.9 Mg 0.9 Na 0.1 Fe 0.1 Si 2 O 6 (labeled as 1) corresponding to 90 mol% diopside-10 mol% aegirine. Although, we obtained transparent and amorphous glass frits after quenching in water, the bulk glass exhibited severe tendency towards surface devitrification immediately after the casting of glass melt on metallic mold.…”

“…The main aim behind scheme of substitutions made in glass 4 and glass 5 is to improve the bioactivity as well as magnetic properties of resultant glass-ceramics as it is well documented in literature that glasses with SiO 2 content higher than 45 wt.% do not exhibit good bioactivity [14] while increasing iron content in the glass is expected to enhance the magnetic properties of samples. It should be noted that although some results pertaining to the sintering and crystallization behavior of glass 1 have been already published in our previous article [11], they have been presented in the manuscript along with a new set of results for the convenience of readers in order to draw the comparisons. Table 1 presents the detailed compositions of all the investigated glasses.…”