Tailored VxOy Metal--Insulator-Transition Oxides for Temperature-Triggered Smart Insulation in Superconducting Coils

Mattia Ortino; Davide Uglietti; Andrea Testino; Nicola Casati; Alexander Steppke; Wiktoria Wnetkowska; Andrea Masi; Kamil Sedlak

arXiv · 2610.16581

Tailored VxOy Metal--Insulator-Transition Oxides for Temperature-Triggered Smart Insulation in Superconducting Coils

Mattia Ortino·Davide Uglietti·Andrea Testino·Nicola Casati·Alexander Steppke·Wiktoria Wnetkowska·Andrea Masi·Kamil Sedlak

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Abstract

Smart insulation is a turn-to-turn layer that insulates in normal operation and conducts only near a hot spot. It could combine the fast ramping of insulated coils with the passive energy dump of non-insulated coils. Metal-insulator transition (MIT) oxides are natural candidates, but the only one tested in a coil so far, V2O3, switches at 150-170 K, far above the 30-70 K window useful for REBCO magnets. We explore the vanadium-oxygen system to lower the transition. TGA redox processing produced multi-phase powders with an effective transition near 127 K, about 25 K below V2O3. Hydrothermal V3O7, hydrated or annealed, was far too resistive and showed no usable transition. V2O3-epoxy specimens provided a robust reference and an acceptance criterion. Cryogenic measurements revealed a reproducible thermal hysteresis, and the measured specific heat of V2O3 corrects earlier model inputs by close to two orders of magnitude. A first electro-thermal model reproduces current sharing through the smart-insulation layer. Doped V2O3 and V8O15 are identified as the next targets.

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Mattia Ortino, Davide Uglietti, Andrea Testino, Nicola Casati, Alexander Steppke, Wiktoria Wnetkowska, Andrea Masi, Kamil Sedlak. 2026-10-12. Tailored VxOy Metal--Insulator-Transition Oxides for Temperature-Triggered Smart Insulation in Superconducting Coils. https://arxiv.org/abs/2610.16581

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