The Solubility Limit of CaO in α‐Alumina at 1600°C

Abstract

The solubility limit of Ca in 99.99% pure α‐Al2O3 (alumina) was measured using a wavelength dispersive spectrometer mounted on a scanning electron microscope. Al2O3 samples were equilibrated at a concentration which ensured saturation of the Al2O3 grains with Ca, and were quenched in water from 1600°C. The results were compared with those from samples which were furnace cooled from 1600°C. For the quenched samples, the Ca solubility limit was found to be 51 ± 1 ppm, which is significantly larger than the solubility limit for samples which were furnace cooled (26 ± 1 ppm).

Encapsulation by segregation – A multifaceted approach to gold segregation in iron particles on sapphire

“…Such transitions may be of a structural and/or chemical nature and were observed in both computer simulations [44] and experiments [45]. Furthermore, they are known to affect important material properties such as GB mobility [46] and diffusivity [47,48]. In the present case, this jump explains the large Au content in the interfacial segregation layer, and might be associated with a change in crystallography of this layer (e.g.…”

Microstructure and phase evolution of Indian magnesite‐derived MgAl2O4 as a function of stoichiometry and ZrO2 doping

“…The microstructure shown in Figure B is typical of commercial n=3.7 spinel . Minor impurity was detected in corundum grain which exceeded solubility limits . Quantity of Si and Ca in spinel also exceeded solubility limit …”

“…18 Minor impurity was detected in corundum grain which exceeded solubility limits. 1,47,48 Quantity of Si and Ca in spinel also exceeded solubility limit. 36,37 B sintered at 1600°C (shown in Figure 4A) consisted of mostly direct bonded, angular, equiaxed grains of mean size 4 lm along with many 10 lm grains and some intergranular porosity, albeit less than A.…”

The combined influence of Mg and Ca on microstructural evolution of alumina

“…This value is higher than the Mg solubility limit measured at the same temperature, using the same method, in a sample that does not contain Ca (132 ppm). In contrast, the solubility limit of Ca in an alumina sample that was co‐doped with Mg and equilibrated at 1600°C is 32 ppm, compared to 51 ppm in an alumina sample that contained only Ca . Therefore, the amount of Mg in solution increases, and that of Ca is reduced, when both Ca and Mg are present in the system.…”

“…In addition to the influence of dopants on the evolving microstructure of alumina, second phase particles and liquid phases can also alter sintering rates, change microstructural evolution, and directly affect the final properties . Control over the formation of secondary phases requires knowledge of the solubility limit of key dopants and impurities at the processing temperatures . A detailed knowledge of the solubility limit of key dopants and impurities also provides the ability to choose between microstructure control via dopants in solution (eg, solute‐drag) vs precipitates of secondary phases (eg, Zener drag) …”