Thermochromic Luminescent Nanomaterials Based on Mn 4+ /Tb 3+ Codoping for Temperature Imaging with Digital Cameras.

A new thermographic nanocrystalline Sr ₄ Al ₁₄ O ₂₅ :Mn ⁴⁺ ,Tb ³⁺ phosphor was developed, and the concentrations of both dopants and the synthesis conditions were optimized. The combination of the thermally quenched luminescence from the Mn ⁴⁺ ions to the almost temperature-independent emission from Tb ³⁺ provides a sensitive luminescent thermometer ( S _R = 2.8%/°C at 150 °C) with strong emission color variability. In addition, a figure of merit for this luminescence thermochromism was proposed, as the relative sensitivities of the x and y CIE coordinates, which for this phosphor reaches at 150 °C S _R ( x ) = 0.6%/°C and S _R ( y ) = 0.4%/°C, respectively. Noncontact thermal imaging was demonstrated with this phosphor using a single consumer digital camera and exploiting the ratio of red (R) and green (G) channels of the RGB images, thereby confirming the high application potential of Sr ₄ Al ₁₄ O ₂₅ :Mn ⁴⁺ ,Tb ³⁺ nanocrystals for thermal sensing and mapping.