Lucalox (General Electric aluminum oxide tubes)

Bob Coble's beryllia-doped alumina sintering process at GE. Used as the canonical example of grain-boundary-motion control enabling full densification — the exception that proves the rule about residual porosity in sintered parts.

There was a faculty member here when I was a student, Bob Coble. He had been at General Electric as a ceramicist — he came out of this department, went there — and he developed a process to take aluminum oxide powder and make it basically a hundred percent dense by putting in beryllia impurities that impeded the grain boundary motion. When they sintered that aluminum oxide tube, they could get a translucent tube, and it was called Lucalox — that was the General Electric name. All the light bulbs around the country, particularly the outdoor ones — the high-pressure sodium vapor lamps — exist because Bob Coble invented Lucalox. Which all had to do with grain boundary motion and sintering. And people didn't care if it wasn't a perfect cylinder, it still held the sodium vapor inside the lamp.