In summary, piezoelectric ceramics are being considered as a potential substitute for muscles in robotic limbs. However, there is a lack of practical use due to the small amount of motion and low work density provided by these devices. Other technologies, such as hydraulic systems, are currently being used to power robotic limbs with sufficient force and speed.
That is such a vague question. You're asking if some type of material that gains charge due to deformation can replicate muscles for a robotic arm. There is no answer to that unless there's some kind of setup that you're just replacing the material with a ceramic. Or am I missing something?
I don't think piezoelectric devices would provide sufficient displacement+force to be of any practical use in robotic devices. The work density is too low. Look at all of the various devices being developed by DARPA...they are still constructed with umbilicals pumping hydraulic fluids to provide sufficient power to move links fast enough, and with enough force.