A transmission electron microscope study of hydrothermally synthesized yttrium disilicate powders

✍ Scribed by I MacLaren; P.A Trusty; C.B Ponton

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 678 KB
• Volume: 47
• Category: Article
• ISSN: 1359-6454
• DOI: 10.1016/s1359-6454(98)00405-4

✦ Synopsis

AbstractÐThe crystallization of three hydrothermally synthesized Y 2 Si 2 O 7 precursor powders at temperatures between 991 and 10388C has been studied using transmission electron microscopy. Powders prepared in acidic or near-neutral conditions were found to be highly inhomogeneous both chemically and microstructurally, with a wide range of crystalline phases formed. In contrast to this, a powder prepared in alkaline conditions was found to be very homogeneous. Small crystalline nuclei were formed in this powder on heating to 10068C which grew rapidly at 10388C to form large single crystal particles. The majority of these had the a-Y 2 Si 2 O 7 phase but some were of the y-Y 2 Si 2 O 7 phase. The reasons for the formation of this y-phase are unclear, although it would be expected to transform to a-Y 2 Si 2 O 7 on further heat treatment at 12008C. Weaknesses in the current crystal structure data for yttrium disilicate phases are identi®ed and suggestions made for rectifying them.