NDLI: Consolidation of polycrystalline yttria powder by MILLIMETER-WAVE sintering for laser host applications

Content Provider	IEEE Xplore Digital Library
Author	Hornstein, Melissa K. Bruce, Ralph W. Fliflet, Arne W. Gold, Steven H. Kahn, Manfred Ashraf Imam, M.
Copyright Year	2007
Description	Author affiliation: Plasma Physics Division, USA (Hornstein, Melissa K.; Bruce, Ralph W.; Fliflet, Arne W.; Gold, Steven H.; Kahn, Manfred) \|\| Materials Science and Technology Division, Naval Research Laboratory, Washington, DC 20375, USA (Ashraf Imam, M.)
Abstract	We report recent results of an investigation of millimeter-wave processing of yttria (Y) for fabrication of transparent, high strength polycrystalline ceramic laser hosts for High Energy Laser (HEL) $applications.^{1,2}$ The objective is to produce polycrystalline materials with optical quality comparable to that of a single crystal. It is difficult to produce yttria single crystals because of the phase transformation around 2000°C and the high melting temperature which is over 2400°C. While single crystals have high thermal conductivity and can operate at high powers, they are costly and limited in size and dopant concentration. Significant advantages of polycrystalline materials compared to single crystals, are lower processing temperature, higher gain as a result of higher dopant concentrations, faster and less expensive fabrication, and the possibility of larger devices. Millimeter-wave processing has been proposed as an alternative method to solve the problems of both conventional vacuum sintering and low frequency microwave sintering, such as low heating rates, poor coupling, and unfavorable thermal gradients. A major component of the NRL millimeter-wave processing facility is a 20-kW, continuous-wave (CW), 83-GHz gyrotron oscillator (GYCOM, Ltd.). Translucent yttria has been successfully sintered with millimeter-wave beams with up to 99% theoretical density. A partially transparent yttria ceramic sample has also been achieved using the millimeter-wave sintering process. Several factors impact the quality of the sintered material including the presence of agglomerates, impurities, processing atmosphere, sintering aids, and thermal gradients. Efforts to improve the transparency are in progress.
Starting Page	1219
Ending Page	1222
File Size	2263249
Page Count	4
File Format	PDF
ISBN	9781424409136
DOI	10.1109/PPPS.2007.4652406
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2008-06-17
Publisher Place	USA
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Powders Ceramics Materials Temperature measurement Heating Electromagnetic heating Millimeter wave technology
Content Type	Text
Resource Type	Article

Sl.	Authority	Responsibilities	Communication Details
1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
2	Indian Institute of Technology Kharagpur	Host Institute of the Project: The host institute of the project is responsible for providing infrastructure support and hosting the project	https://www.iitkgp.ac.in
3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
5	Website/Portal (Helpdesk)	Queries regarding NDLI and its services	support@ndl.gov.in
6	Contents and Copyright Issues	Queries related to content curation and copyright issues	content@ndl.gov.in
7	National Digital Library of India Club (NDLI Club)	Queries related to NDLI Club formation, support, user awareness program, seminar/symposium, collaboration, social media, promotion, and outreach	clubsupport@ndl.gov.in
8	Digital Preservation Centre (DPC)	Assistance with digitizing and archiving copyright-free printed books	dpc@ndl.gov.in
9	IDR Setup or Support	Queries related to establishment and support of Institutional Digital Repository (IDR) and IDR workshops	idr@ndl.gov.in