What is dielectric constant and relaxation time?

What are some concrete examples where dielectric relaxation becomes relevant to materials science?

• Answer:

  High frequency capacitors. Anything that uses a high frequency capacitor needs a dielectric material with a fast relaxation time or else the dielectric looses performance. Dielectric materials work by polarizing themselves in the presence of an applied electric field. This polarization helps the conducting plates of the capacitor pile on more charge by stabilizing the high charge density on the plate with an opposite charge in the dielectric. The dielectric cannot conduct by itself so there is no net motion of charges in the material over time, just a slight motion that allows the material to polarize. Just about any modern electronic device uses capacitors in some way and some of them require charging and discharging at high frequencies. One application is in DRAM, which is in just about every computer today. DRAM basically works by using small capacitors to represent 1's and 0's by either being charged or discharged. A dielectric with a long relaxation time will perform very poorly in such circumstances. DRAM Up Close Sources: http://www.eetimes.com/document.asp?doc_id=1276895