  Nb$_3$Sn has great potential to become the material of choice for fabrication
of SRF cavities. The higher critical temperature of Nb$_3$Sn potentially allows
for an increased operational temperature in SRF cavities, which could enable
tremendous simplification of cryogenic system, leading to significant cost
reduction. We present extended characterization of a Nb$_3$Sn coated Nb cavity
prepared at Cornell University. Using combination of thermometry during cavity
RF measurements, and structural and analytical characterization of the cavity
cutouts, we discover Nb$_3$Sn coating flaws responsible for the poor cavity
performance. Our results clearly show degraded material quality in the cavity
cutouts which exhibit significant heating during the RF testing. Results of
extended comparison of cavity cutouts with different dissipation profiles not
only point out the cause of significant Q-slope but also establish figures of
merit for material qualities in relation to the quality of SRF performance.
