All of us have used batteries and electric wires of some sort. Most of us know that a flow of electric charges (called 'current') occurs through the wire, when the two ends of the wire are rigged up to the battery. What happens when you use a insulating wire? It turns out that the battery still does its job of setting up a gradient of electric potential across the wire, but the wire just does not respond! (by definition, this is what insulators do) The electrons making up the wire however are however displaced from their equilibrium position. That is to say, they are displaced by a bit, in response to the applied field. This means that there is a net displacement of electric charges within the wire, in response the the applied field, even though there is no observable current. If you remove the field now, the charges would go back to their equilibrium positions, leading to a "discharge" event. Insulating materials that can be charged and discharged this way are called dielectrics. These materials can be used as reservoirs of charges; in conventional electrical engineering, these reservoirs of charge are called "capacitors". For more about this subject, do consult the wikipedia article on "capacitors".
Many crystalline ceramics (which simply means materials whose cooking requires high temperatures) can be charged and discharged this way. Most well known and commercially used dielectrics contain lead, which is is extremely toxic, and damages the human brain. One of our projects concerns materials that can be used to replace these lead containing dielectrics.
With regards to lead-free dielectrics, the material of choice for us is a bit complicated, and has the longish name "sodium bismuth titanate". You may want to remember it, if you want to impress your friends!
To sodium bismuth titanate, we add an element called Europium. It turns out that this mix of materials emits red light very efficiently, when excited suitably (electrically or using some other light source). Our colleague, Prof. U. Ramamurty, was curious to study the mechanical behavior of these new ceramics we had made. To our surprise, we found that the mechanical properties and optical properties follow trends that mirror one another! This was fascinating to us, and we reported this, along with a plausible explanation for the observed phenomenon. For more information about this, please do consider reading the paper we wrote.
Ref: Solid State Communications 173, 38–41 (2013)
