Solubility Limit of MgO in Al₂O₃ at 1600°C

Abstract

The solubility of Mg in alumina was measured using wavelength‐dispersive spectroscopy mounted on a scanning electron microscope. Careful calibration of the microscope's working conditions was performed in order to optimize the detection limit and accuracy. Measurements were conducted on water‐quenched and furnace‐cooled samples, without any thermal or chemical etching to avoid alteration of the bulk concentration. The results indicate the solubility limit of Mg in alumina to be 132±11 ppm at 1600°C.

Atomistic modeling of dopant segregation in α-alumina ceramics: Coverage dependent energy of segregation and nominal dopant solubility

“…6 There is agreement with the fact that high energy boundaries more easily accommodate dopants in various complexions, whereas low energy boundaries are more prone to second phase precipitation. 3 Solubilities found in the literature are similar with 2-3 Mg/nm 2 at 1600 • C. 51 Mg enrichment (x i /x b ) was reported to be 400 within a grain boundary region of 1 nm in Mg saturated ␣-alumina. 53 Depending on whether a bulk saturation concentration of 132 ppm 51 or 300 ppm 58 is considered, this would correspond to a grain boundary concentration of 2.5 Mg/nm 2 or 5.7 Mg/nm 2 respectively.…”

“…3 Solubilities found in the literature are similar with 2-3 Mg/nm 2 at 1600 • C. 51 Mg enrichment (x i /x b ) was reported to be 400 within a grain boundary region of 1 nm in Mg saturated ␣-alumina. 53 Depending on whether a bulk saturation concentration of 132 ppm 51 or 300 ppm 58 is considered, this would correspond to a grain boundary concentration of 2.5 Mg/nm 2 or 5.7 Mg/nm 2 respectively. The agreement between predicted and measured grain boundary solubilities is therefore reasonably good when considering again the more general subset of high-energy, high-Σ boundaries and the lower bulk solubility.…”

“…34) albeit smaller than lanthanides is still larger than the aluminum ion. Grain boundary [51][52][53] and surface [54][55][56][57] segregation of Mg still occurs, the extent being less pronounced than for the larger elements considered above. Experimental values for the Mg bulk solubility in ␣-alumina vary substantially; the most recent value found in the literature (132 ± 11 ppm at 1600 • C) was measured using a wavelength dispersive spectroscopy, 51 whereas Roy and Coble 58 reported a solubility limit of 300 ppm at 1630 • C based on spectrochemical analysis.…”

“…51,58 Fig. 8 therefore contains a solubility curve calculated with the lower solubility (132 ppm) reported by Miller et al 51 (dashed grey line), as well as one computed using the higher (300 ppm) bulk solubility by Roy and Coble 58 (solid black line). Also shown are experimental observations of conditions under which precipitation was or was not observed as reported in various Mg doped samples.…”

Effects of TiO2 addition on the phase, mechanical properties, and microstructure of zirconia-toughened alumina ceramic composite

“…The solubility limit achieved in this work may not be in agreement with some studies. This might be explained by the smaller particle size of Al 2 O 3 and TiO 2 used [13,20] and the presence of YSZ in the composite. The enlarged section of XRD patterns at (020) peak representing the formation of Al 2 TiO 5 is seen in Fig.…”