Yes this is normal but it will depend not of the voltage but of the amp of the charger.
i.e. charging with a 2 amp charger will make your device become warmer on the back (battery) and the charge of your phone will be quick, on the other hand charging with a 750ma (0.75a) the phone will be just a little warm and the full charge will be longer.
Is it recommended to use a strong charger? => not sure! => some people say this can damage your battery, => not sure because I have charged my 1320 now for more than 1 year with a 2 amp charger and the phone still hold the charge 1 to 2 days.