Semiconductors—
Some ceramics are semiconductors. Most of these are transition metal oxidesthat are II-VI semiconductors, such as zinc oxide.
Excellent post from @Pezz69 this morning in ADN , re : Semiconductors.
While there are prospects of mass-producing blueLEDsfrom zinc oxide, ceramicists are most interested in the electrical properties that showgrain boundaryeffects.
One of the most widely used of these is the varistor.
These are devices that exhibit the property that resistance drops sharply at a certain voltage threshold .Once the voltage across the device reaches threshold voltage threshold, there is a breakdown of the electrical structure in the vicinity of the grain boundaries, which results in its electrical resistance dropping from several megohms down to a few hundred ohms.
*The major advantage of these is that they can dissipate a lot of energy * , and they *self-reset - after the voltage across the device drops below the threshold, its resistance returns to being high* .
This makes them ideal for *surge-protectionapplications* ; as there is control over the threshold voltage and energy tolerance, so they find use in all sorts of applications.
The best demonstration of their ability can be found in electrical substations, where they are employed to protect the infrastructure fromlightningstrikes.
They have rapid response , are low maintenance, and do not appreciably degrade from use, making them *virtually ideal devices for this application* .
Semiconducting ceramics are also employed as *gas sensors*. When various gases are passed over a polycrystalline ceramic, its electrical resistance changes.
With tuning to the possible gas mixtures, very inexpensive devices can be produced.”
James Marsh yesterday referred to being in talks for BOAs and how marketing of product is tricky though broad interest and significant markets . But he talked about how important the electrical ceramics market is also for contracts for Great White high grade Halloysite kaolin product.
People tend to think of “high grade ceramics” as being porcelain vases and high quality porcelain china cups!
https://hotcopper.com.au/threads/general-comments-chat.4779186/page-21384?post_id=53006387
