The TAJC475K020HNJ: This is a 4.7 µF molded tantalum capacitor rated at 20 V, ±10% tolerance, in the TAJ series from KYOCERA AVX. For a 100 kHz buck converter, the ripple voltage across this cap is the product of the ripple current and the ESR; a lower ESR part would run cooler but this one fits the budget for a general-purpose rail.
-55 to 125 °C — full military temp range
The 2000-hour life at max temp is the derating anchor: at 85 °C the expected life is significantly longer, but the BOM planner should budget the application's thermal profile against this floor.
Listed as Active. No last-time-buy window to track, no successor to qualify. Store the reels dry — the molded case is not hermetic, and moisture ingress accelerates leakage current over time.