Solid materials with dipolar molecules

Question

I am trying to heat solids using controlled microwave radiation and I am therefore looking for materials that absorb microwaves well. I have understood that for radiation in the radio frequency and microwave frequency regimes the polarity of molecules and the conductivity are most important. I am also reading this chapter about dry solids (A. C. Metaxas & R. J. Meredith. Industrial Microwave Heating. 1983.):

2.8 Dry, non-conducting dielectrics

Emphasis has been given so far to the conducting phase in dielectrics such as, for example, water, because high frequency heating has been applied very successfully to many drying applications. However, many applications require heating of dry, non-conducting insulators such as natural rubber or other chemical substances, in order to achieve specific reactions within the material. In this case, Maxwell— Wagner type effects, in the absence of any trace impurities, play no part at all in the heating process which is now governed solely by dipolar effects. In fact, if the insulating material is non-polar, one may deliberately introduce a controlled proportion of conducting particles, such as carbon black, to enhance the absorption of the applied high frequency energy by the material to be heated. This is discussed further in Section 3.9.

From this section I understand that it's possible to mix carbon into materials that are non-polar and non-conductive to make them absorb microwaves and I feel like this would be the case if I want to heat plastics for example. But my question is: are there (common) solids that are non-conductive but have polar molecules, so that they would also be suitable for microwave heating? And could they potentially have a higher absorption than conductive materials?

And does anyone know of any other absorbent solids?

I am thankful for any help!

Answer 1

Though not a material consisting of individual molecules like e.g., glucose, try silicon carbide ($\ce{SiC}$).

This material not only became popular because it is a good absorber of microwave reaction, but equally because of its high mechanical strength, high melting point, and low chemical reactivity. These render $\ce{SiC}$ you might heard about earlier (abrasives, pads for breaks, heat filaments, etc.) suitable for (small) chemical reactors, too.

(taken from an overview by Anton Paar)

(Kappe, Acc. Chem. Res. 2013)

Since it is equally commercially available as shot and powder, you could blend it as a dispersion into a solid matrix, too. Then, $\ce{SiC}$ were the antenna heating from inside of your sample.

Kappe, C. O. Unraveling the Mysteries of Microwave Chemistry Using Silicon Carbide Reactor Technology. Acc. Chem. Res. 2013, 46, 1579–1587; doi 10.1021/ar300318c.