Design of core–shell lanthanide fluorides for real-time temperature monitoring of metal components

Precision mechanical equipment frequently experiences efficiency degradation and functional deterioration due to heat generation in specific components during prolonged operation. The application of non-contact temperature monitoring based on rare-earth luminescent centers enables real-time monitoring of the operational status of precision components, serving as an effective preventive strategy against equipment failure. In this work, we introduce a novel rare earth fluoride material, denoted as NaLuF 4 :Yb, Er@NaLuF 4 :Yb,Nd, which exhibits both high luminescent intensity and thermal sensitivity, making it well-suited for temperature detection on various metal surfaces. The large single-particle size and the core-shell-like structure formed via surface ion exchange are key structural features that contribute to these properties. Under 808 nm or 980 nm light excitation, Nd 3+ or Yb 3+ absorb energy, which is subsequently transferred to Yb 3+ through an interfacial energy transfer mechanism, ultimately resulting in the upconversion luminescence of Er 3+ . The spatial separation between Nd 3+ and Er 3+ enhances the luminescent intensity of Er 3+ and improves thermal sensitivity, achieving outstanding performance within the temperature range of 298 K to 398 K. This improvement in thermal sensitivity is attributed to the independent temperature-dependent processes induced by the spatial separation. Through compatibility testing with various metal surfaces, this class of materials demonstrates significant potential for application in temperature-sensing components of mechanical equipment.