  We quantify the spin Hall angle {\theta}SH and spin diffusion length lsd of
Nb from inverse spin-Hall effect (iSHE) measurements in Nb/Ni80Fe20 bilayers
under ferromagnetic resonance. By varying the Nb thickness tNb and comparing to
a Ni80Fe20/Pt reference sample, room temperature values of {\theta}SH and lsd
for Nb are estimated to be approximately -0.001 and 30 nm, respectively. We
also investigate the iSHE as a function of temperature T for different tNb.
Above the superconducting transition temperature Tc of Nb, a clear
tNb-dependent T evolution of the iSHE is observed whereas below Tc, the iSHE
voltage drops rapidly and is below the sensitivity of our measurement setup at
a lower T. This suggests the strong decay of the quasiparticle (QP)
charge-imbalance relaxation length across Tc, as supported by an additional
investigation of the iSHE in a different sample geometry along with model
calculation. Our finding suggests careful consideration should be made when
developing superconductor spin-Hall devices that intend to utilize QP-mediated
spin-to-charge interconversion.
