Is it possible to charge a capacitor to any potential? Does it depend on the dielectric placed between them?

Is it possible to charge a capacitor to any potential? Does it depend on the dielectric placed between them? Or, are there other factors affecting it?

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So now if it is not a parallel plate capacitor..its a solid sphere with radius R...can it be limitlessly charged? – Prakash Regmi Jan 19 '13 at 13:51
No, at some point the electric field inside the insulator becomes large enoughy to make it a conductor, and the charge will dissipate. – jkej Jan 19 '13 at 14:46