What is the name of the bond between phosphate and the sugar in a nucleotide?
Phosophoester is a valid term. There are at least a 1000 peer-reviewed articles that use this term. IUPAC Goldbook defines nucleotides as: 


  Compounds formally obtained by esterification of the 3 or 5 hydroxy group of nucleosides with phosphoric acid. They are the monomers of nucleic acids and are formed from them by hydrolytic cleavage."


Phosphoester or phosphoric ester means an ester of phosphoric acid.