Thermophysical Properties of Niobium (1000–2700 K): Multi-stepwise Pulse-Heating Measurements with Consistency Validation via a Revised Emissivity–Resistivity Relation

Abstract Thermophysical properties of niobium were measured from 1000 K to 2700 K using a multi-stepwise pulse-heating technique that enables quasi-static and dynamic evaluations within a single heating sequence. Electrical resistivity, hemispherical total emissivity, specific enthalpy, and isobaric heat capacity were obtained, and the difference between enthalpy values obtained from quasi-static and transient analyses served as an internal indicator of time-scale-dependent effects, especially near $${T}_{\text{m}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>T</mml:mi> <mml:mtext>m</mml:mtext> </mml:msub> </mml:math> . To assess cross-property consistency, we re-derived a Schmidt–Eckert relation using Fresnel-based optical modeling with Planck-weighted hemispherical integration, providing a resistivity-derived emissivity reference over the present $$\rho T$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>ρ</mml:mi> <mml:mi>T</mml:mi> </mml:mrow> </mml:math> range. The calorimetrically measured emissivity agrees with the Drude/Hagen–Rubens-based reference over 1400–2300 K, defining an intrinsically reliable window for emissivity-corrected heat capacity evaluation, while data up to 2700 K remain practically usable for engineering applications when their expanded combined uncertainties are considered. Within these validated limits, working enthalpy and heat capacity were obtained with expanded combined uncertainties ( k = 2) of ~ 2.9 % and ~ 2.0 %, respectively. This combined strategy—time-scale analysis plus resistivity-based validation—strengthens confidence in pulse-heating thermophysical data and provides insight into near- $${T}_{\text{m}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>T</mml:mi> <mml:mtext>m</mml:mtext> </mml:msub> </mml:math> behavior of refractory metals.