Writing of the Technological Innovation WebsiteA known and widely used material in the field of microelectronics and thermoelectric generation can also function as an efficient controller for heat transfer.This new class of material creates the possibility of increasing or decreasing thermal conductivity on demand, transforming a thermal insulator into a thermal conductor and vice versa.An on/off switch for heat will have large-scale applications, from electronic devices and power generators to building greener buildings and new space technologies - switches to turn off the heat already exist, but here it is a single material of solid state.Bidirectional control of heat through adjustable thermal conductors will be especially useful in artificial satellites and space robots, which need to operate in extreme temperatures, withstanding the heat when they are facing the Sun and the cold of space when they are on the night side."This new heat management mode is substantially less complex and means that heat regulation is easier to manage - and faster. Where a radiator or insulation takes a long time to start heating or cooling, the solid state engine would be almost instantaneous. Being able to keep up with rapid temperature changes also makes things safer. Because heating and cooling can be monitored, the chances of heat or cold causing it to malfunction - or worse - decrease," Kiumars said. Aryana, from the University of Virginia, USA.Adjustable thermal conductivityThe controllable thermal conductor discovered by Aryana is a very pure sample of lead zirconate (PbZrO3), an antiferroelectric material.A ferroelectric material is like a magnet, except that instead of a north and south pole, it has a positive and a negative charge.Simply subject it to an electric field so that it reverses its polarity to the opposite state, which will remain stable until another electric pulse is applied.In an antiferroelectric material, however, both an electric field and heat can act."Typically, thermal conductivity is considered a static property of the material. If you want to transform a thermal conductor into an insulator, you need to permanently change its structure or integrate it into a new material," explained Professor Patrick Hopkins.But that's not what the team recorded when they used an ultrapure sample of lead zirconate."What this interesting material does, in addition to being a high-quality crystal that has thermal conductivity tendencies like amorphous glass, and being solid-state, is it gives us two unique buttons to change the thermal conductivity," said Hopkins."We can quickly heat the crystal with a laser or apply [electrical] voltage to actively adjust thermal conductivity and heat transport."With a single laser pulse, the team achieved a 38% bi-directional change in the material's thermal conductivity.The structures of antiferroelectric materials are bidirectional in nature.In the smallest repeating unit of the crystal lattice, one half has a polarity pointing up and the other half pointing down, so the positive and negative charges cancel each other out.When heated, the crystal structure changes and antiferroelectricity disappears, increasing thermal conductivity.Applying an electric field does the opposite - it causes the material to change to ferroelectric and the thermal conductivity to decrease.Mains polarity returns to zero when voltage is removed.To make the expected impact on the technologies, the team will now need to build a larger heat on/off switch to quickly move or store an even greater percentage of heat.The next steps will include better defining the possibilities and limitations of the material, eventually designing a new composite material with higher switching rates, paving the way for actively tunable thermal conductivity materials.