Learning from Precedent Environment-Adaptable-Materials and -Sensors

Abstract

This article briefly describes a history of the development of Fe-Ni Invar alloys whose temperature dependence of thermal expansion and elastic constants are extremely small: they have been used for a international metric standard and several precision instruments. It also describes a brief concept of low temperature thermometers whose electrical resistance are markedly dependent on temperature but independent on magnetic field: they can be used in a superconducting magnet. These characteristics are based on competing effects: anharmonic lattice vibration and magnetostriction in the former, while electron scattering and electron localization by low dimensionalities and random distribution of lattice impurities in the latter. The two examples presumably give researchers and engineers in the fields of calorimetric and thermal analyses some hints and guiding principles for developing environment-adaptable materials and sensors.