Pushing the Limit of Boltzmann Distribution in Cr3+-Doped CaHfO3 for Cryogenic Thermometry

This is the authors' abstract. We don't add key points for this paper.

Luminescence Boltzmann thermometry is one of the most reliable techniques used to locally probe temperature in a contactless mode. However, to date, there is no report on cryogenic thermometers based on the highly sensitive and reliable Boltzmann-based 4 T 2 → 4 A 2 / 2 E → 4 A 2 emission ratio of Cr 3+ . On the basis of structural information of the local HfO 6 octahedral site we demonstrated the potential of the CaHfO 3:Cr 3+ system by combining deep theoretical and experimental investigation. The material exhibits simultaneous emission from both the 2 E and 4 T 2 excited states, following the Boltzmann law in a cryogenic temperature range of 40–150 K. The promising thermometric performance corroborates the potential of CaHfO 3:Cr 3+ as a Boltzmann cryothermometer, being characterized by a high relative sensitivity (∼ 2%·K –1 at 40 K) and exceptional thermal resolution (0.045–0.77 K in the 40–150 K range). Moreover, by exploiting the flexibility of the 4 T 2 - 2 E energy gap controlled by the crystal field of the local octahedral site, the design proposed herein could be expanded to develop new Cr 3+ -doped cryogenic thermometers.