Dual-emission luminescence thermometry using LaGaO3:Cr3+, Nd3+ phosphors

A series of La1-xGa0.99O3:Cr-0.01, Nd-x phosphors (where x = 0.005, 0.01, 0.02) for luminescence thermometry was synthesised by the solid-state method, structurally characterised using powder X-ray diffraction data, and investigated by ambient and variable-temperature optical measurements. The design principle relies on the use of a combination of transition metal and rare earth activator ions such that the excitation and emission wavelengths fall within the near infra-red spectral region, notably in the 'first biological window' that is attractive for potential in vivo applications. The photoluminescence spectra of the compounds feature the characteristic E-2 phosphorescence of Cr3+ at 729 nm and the F-4(3/2) -> I-4(9/2) emission of Nd3+ around 890 nm. The Nd3+ emission is quenched at a higher rate than that of Cr3+ with increasing temperature. Thermometric analysis by monitoring the luminescence intensity ratio (LIR) between the emissions of Cr3+ and Nd3+ from 300 K to 650 K shows a quasi-Boltzmann trend, with a maximum relative sensitivity of similar to 2% K-1, high absolute sensitivity values over this entire temperature range, excellent temperature resolution of 0.04 K at room temperature, and high stability.

Automated summary

A series of La1-xGa0.99O3:Cr-0.01, Nd-x phosphors were synthesized for luminescence thermometry. The compounds feature near infra-red emissions from transition metal and rare earth activator ions, making them attractive for potential in vivo applications. The thermometric analysis showed high sensitivity, excellent temperature resolution, and high stability by monitoring the luminescence intensity ratio between Cr3+ and Nd3+ emissions.