1 µF, 10 V tantalum — the decoupling workhorse for tight boards
The TAJS105K010RNJ: This is a 1 µF ±10% molded tantalum capacitor rated at 10 V DC, built in the standard 1206 (3216 Metric) surface-mount footprint. It belongs to the TAJ series from KYOCERA AVX, a general-purpose line that covers the bulk of board-level decoupling and filtering needs across consumer, industrial, and automotive temperature domains. The 25 Ohm ESR (equivalent series resistance) is a typical figure for a small-case tantalum at this capacitance and voltage. For a 1 µF part used as a local decoupling cap near a digital IC, that ESR is acceptable — the ripple current at the switching frequencies involved is low enough that self-heating stays under control. If you are filtering a higher-ripple rail, the ESR becomes a design constraint: the I²R power loss scales with ripple current, and the cap's own temperature rise adds to the ambient.
That 125°C upper limit is the absolute maximum ambient the part is designed to see — at sustained 125°C the leakage current and failure rate increase, so derating the applied voltage to 50% of rated (5 V or less) is standard practice for long-life designs in hot environments.