The phrase "a key device to" is correct and usable in written English.
It can be used when discussing an important tool or method that serves a specific purpose or function in a particular context.
Example: "The new software serves as a key device to enhance productivity in the workplace."
Alternatives: "an essential tool for" or "a crucial means to".
The key device to achieve this, introduced in this review, is to convert the utilitarian formulation of classical economic theory, in which choices are assumed to maximise expected utility, into a pure (Bayesian) inference problem.
As the federal and congressional probes continue into the causes of the Gulf oil rig explosion, new information is coming to light about the failure of a key device, the blowout preventer, to shut off the gushing well, which could have prevented the growing catastrophe.
The sheer number of new characters, alongside guest star Sharon D Clarke, necessarily means that the alien menace is more of a low-key device to bring the characters together and introduce them to us, than a world-ending threat.
There are also power strips that shut off when a key device is turned off, so that if you turn off your TV, the strip also cuts power to your cable box, gaming console and DVD player.
"And it then became a key device in the production, and indeed in how the audience understands it".
Polyethylene-based microporous membrane separators are a key device for lithium-ion secondary batteries (LIBs).
Metaphor is a key device for suggesting worth (a reciter might call himself a ferocious animal), and poetic license is granted for coining new words.
This novel, with its reliance on literary parody, was a turning point: serious use of parody thereafter became a key device in Nabokov's art.
In petroleum refining industry, external catalyst cooler is a key device in FCC units processing heavy residue feedstock.
