  This study of highly accelerated lifetime tests of SrTiO$_3$, a model
semiconducting oxide, is motivated by the interest in reliable multilayer
ceramic capacitors and resistance-switching thin-film devices. Our analytical
solution to oxygen-vacancy migration under a DC voltage -- the cause of
resistance degradation in SrTiO$_3$ -- agrees with previous numerical
solutions. However, all solutions fail to explain why degradation kinetics
feature a very strong voltage dependence, which we attribute to the nucleation
and growth of cathode-initiated fast-conducting needles. While they have no
color contrast in SrTiO$_3$ single crystals and are nominally invisible,
needles presence in DC-degraded samples -- in silicone oil and in air -- was
unambiguously revealed by in-situ hot-stage photography. Observations in
silicone oil and thermodynamic considerations of voltage boundary conditions
further revealed a cooccurrence of copious oxygen bubbling and the onset of
final accelerating degradation, suggesting sudden oxygen loss is a precursor of
final failure. Remarkably, both undoped and Fe-doped SrTiO$_3$ can emit
electroluminescence at higher current densities, thus providing a vivid
indicator of resistance degradation and a metal-to-insulator resistance
transition during cooling. The implications of these findings to thin ceramic
and thin film SrTiO$_3$ devices are discussed, along with connections to
similar findings in likewise degraded fast-ion yttria-stabilized zirconia.
