Overview of progress in strengthening sapphire at elevated temperature

Daniel C. Harris

doi:10.1117/12.354609

26 July 1999 Overview of progress in strengthening sapphire at elevated temperature

Daniel C. Harris

Proceedings Volume 3705, Window and Dome Technologies and Materials VI; (1999) https://doi.org/10.1117/12.354609
Event: AeroSense '99, 1999, Orlando, FL, United States

Abstract

Loss of mechanical strength at high temperature limits the thermal shock resistance of sapphire IR windows and domes. The critical weakness is loss of compressive strength along the c-axis of the crystal. Compression causes twinning in the crystal. When twins intersect, a fracture forms at the intersection. The fracture initiates mechanical failure if sufficient tensile stress is present. Twinning is a property of the perfect crystal. Strategies for increasing the high- temperature compressive strength of sapphire are based on introducing crystal defects to inhibit twinning. Doping with Mg²⁺ or Ti⁴⁺ can double the compressive strength at 600 degrees C. Ion implantation increases the tensile strength by a factor of 2 at 300 degrees C. Placing a thin sheet of graphite between sapphire and the test fixture in mechanical tests apparently reduces contact compressive stresses and increases the apparent strength of sapphire in many kinds of mechanical tests at 600 degrees C.

Citation Download Citation

Daniel C. Harris "Overview of progress in strengthening sapphire at elevated temperature", Proc. SPIE 3705, Window and Dome Technologies and Materials VI, (26 July 1999); https://doi.org/10.1117/12.354609

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available