Phase Formation and Sintering of YAG Ceramics
Open Access
- Author:
- Kochawattana, Sujarinee
- Graduate Program:
- Materials Science and Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- October 26, 2007
- Committee Members:
- Gary Lynn Messing, Committee Chair/Co-Chair
William Blaine White, Committee Member
James Hansell Adair, Committee Member
Elizabeth C Dickey, Committee Member
Venkatraman Gopalan, Committee Member - Keywords:
- phase formation
sintering
YAG - Abstract:
- In recent years, YAG (Yttrium aluminum garnet; Y3Al5O12) laser materials have been applied in various fields including medical operation, metal machining and semiconductor processing. Reactive sintering is the process of interest as it is the most suitable process for mass scale production. However, to achieve the optically transparent quality, 2 important topics related to reactive sintering of YAG are needed to be understood; first, the phase formation of the reaction between the starting powders and second, sintering mechanisms. In the present work, the kinetics and mechanisms of phase formation during heat treatment of Y2O3 and Al2O3 powders to form YAG (Yttrium Aluminum Garnet, Y3Al5O12) were studied. Quantitative X-ray analysis by Rietveld refinement was used to follow formation of YAM (Y4Al2O9), YAP (YAlO3) and YAG. Reduction of the size of both Y2O3 and Al2O3 powders increases the formation rate of YAG. Direct reaction between alumina and yttria to form YAG was not observed in this study. Furthermore, Densification and grain growth in pure YAG, SiO2 doped YAG and SiO2 doped Nd:YAG were explored. The stability of large pores underscores the importance of forming in transparent YAG applications. Addition of SiO2 and Nd2O3 enhance densification rate due to the formation of liquid phase during sintering. Addition of SiO2 increases growth rate. Addition of Nd2O3 further enhances grain growth but above 1700„aC, higher Nd3+ content suppress grain growth possibly due to the solute drag. In addition, the transmittances of YAG samples in this work were examined.