I know that a verb and "not" are usually contracted when together in a negative interrogative sentence. Example:
Aren't they lovely?
Is it grammatically wrong to avoid the contraction? Example:
Are not they lovely?
It's not necessarily grammatically wrong, but the order you've presented is not idiomatic and would strike my ear as possibly archaic. The idiomatic version places the subject between the verb and the negation.
Aren't they lovely? becomes Are they not lovely?
See a famous version of this from the movie Gladiator:
Are you not entertained? Is this not why you're here?