One often sees assertions that these are "necessary" for modern military and consumer computing applications. I presume that without these rare metals, the devices could be manufactured, but would be larger and/or more expensive. Is this true?
Sort of, it seems.
First, I am not an expert at this topic at all. I started to use google and first found this article Computers without rare earths are huge which suggests that computers CAN be build without the use of rare earths, but would be significantly bigger. This may have a huge impact as today every vehicle, airplane or device is packed with multiple tiny computers. Large computers mean we can't utilize computational power to support/improve navigation, life support, etc. on airplanes and surely cant carry our smartphone with us. Furthermore the article suggests, that rare earth also improve efficiency of computing devices.
Then I found these articles Alternatives to rare earths More alternatives which suggest that one can indeed achieve the same or a similar level of size reduction and efficiency with alternative materials. As the supply of rare earths is not guaranteed long term (mining is not environmental friendly, there are territorial disputes etc.) researchers are working on the two obvious possibilities:
- Develop the current technology to work without rare earths (or materials not yet considered rare earths)
- Engineer new elements that have a similar effect (i.e. in magnets)
To sum it up: it seems like its not possible at the moment, but might become feasible in a few years (or decades).
Disclaimer: please be aware that neither this answer nor the articles provided are scientific evidence. (I am also not sure if this is the right forum to ask this)
It's not that it's not possible, it's that it won't be cheap. I'm going to focus on a very specific rare earth metal - Tantalum. This is used to make Tantalum capacitors. Tantalum capacitors are special not because they work better as capacitors than the basic, cheap caps you can buy, but because they have very tightly controlled properties. One of the big ones is called In-Series Resistance (ISR) - a capacitor isn't just a capacitor, it has a resistance as well. This resistance needs to be tightly controlled, especially at high speeds/power, since a resistor in series with a capacitor can affect timing among other things. Tantalum caps are just easy to manufacture to more tightly controlled standards. They are much more expensive, however.
So what you'd need is to create a capacitor using non rare earths that also are produced in a tightly controlled way to emulate the ISR of a tantalum cap. That's probably not impossible, but the manufacturing methods would have to be refined and I'll wager that it would cost more due to the stricter tolerances needed on cheaper materials.
There are other examples of metals being used in the circuits of a computer because they have desirable electrical properties. It is highly likely that the average computer user might not even notice if you replaced, say, the gold plating of a CPU's pins with cheaper tin, but there would be performance hits all around.
Ultimately, a computer can be built from many things, so creating a rare earth free computer is probably not a huge technical challenge. Instead, it's far more likely that the absolute cutting edge of speed, size, power, and weight would have to be rolled back a few generations.