Growth kinetics of spherulitic apatite in some MgO-CaO-SiO2-P2O5glasses

✍ Scribed by Jiin Jyh Shyu; Jenn Ming Wu

• Publisher: Springer
• Year: 1994
• Tongue: English
• Weight: 953 KB
• Volume: 29
• Category: Article
• ISSN: 0022-2461
• DOI: 10.1007/bf00356658

✦ Synopsis

Crystallization of glasses with compositions (wt%) of 11.2 MgO, 33.3 SiO2, CaO, and xP20 ~ (x=18.3, 16.65, 15.825 and 15.0) resulted in a spherulitic apatite phase with different crystal morphologies. An ellipsoidal morphology was observed for x= 18.3, 16.65 and 15.825, and an anomalous morphology was observed for x = 15.0. A metastable phase, which was similar in some characteristics to apatite, was also found for x= 15.0. The growth kinetics of the spherulitic apatite crystals were investigated to explain the above observations. Both the dendrite arms along the [0001] and [1 1 20] directions of the apatite crystals showed constant growth rates in each glass. Growth-rate anisotropy was found between these two directions. The ellipsoidal shape of the apatite crystals is explained by this growth-rate anisotropy. The growth rates, and the growth-rate anisotropy, varied with the P205 content in such a manner that the changes in phase formation behaviour can be explained on the basis of the kinetic results.