Isotopes of yttrium
Natural yttrium is composed of the single stable isotope, 89Y. The most stable radioisotopes are 88Y, which has a half-life of 106.63 days, and 91Y, with a half-life of 58.51 days. All the other isotopes and isomers have half-lives of less than 15 hours, except 87Y with 79.8 hours and 90Y with 64.05 hours. The dominant decay mode below the stable 89Y is electron capture to isotopes of strontium and the dominant mode after it is beta emission to isotopes of zirconium.
In total, the isotopes characterized range from 76Y to 109Y.
In products of nuclear fission, 90Y exists in equilibrium with its parent isotope strontium-90. This isotope alone is also used in medicine; see yttrium-90.