electrostrictive materials

Yes. Wikipedia can.

Do you mean electrophoretic materials? Look up "electrophoresis" on Wikipedia.

Tungsten is an example of a material which changes resistance positively with heat, sometimes caused by electrical current flowing through it, often found in things like incandescent light bulbs.

Try here.

Well, if no one else did, I learned something! I have not heard of eletrostrictive materials before. Good answer!

thank u for ur response. i need some of the info about the availability of these electostrictive material as a raw material but not in the form of actuators or devices. Through my most searches, I found only the products based on these materials. Could u kindly help me where it is available as a solid rods or bar, etc,?

First of all, I don't know anything about electrostrictive material. I simply performed an internet search. Secondly, I don't believe it occurs as a "raw material". It appears to be mostly ceramic with traces of other materials.

Why don't you contact LUEC who seem to have been involved with this stuff for over 15 years? I'm, pretty sure they can answer your questions better than I.