A highly sensitive lifetime-based luminescent manometer and bi-functional pressure–temperature sensor based on a spectral shift of the R-line of Mn4+ in K2Ge4O9

Abstract

Although lifetime-based luminescent manometers exploiting the luminescence kinetics of Mn⁴⁺ ions exhibit remarkably attractive manometric performance, the number of studies reported in the literature devoted to this area is relatively small. Given that this type of manometer can exhibit very high sensitivity over a limited pressure range, in-depth studies on the correlation of the structure with the manometric properties of such pressure gauges are required to enable the design of manometers with predefined sensing performance. In response to these requirements, the present work investigates the spectroscopic properties of a new promising inorganic phosphor, i.e. K₂Ge₄O₉:Mn⁴⁺, measured as a function of pressure and temperature. As is shown, the spectral shift of the Mn⁴⁺ R-line, the ratio of its emission intensity to phonon-progression bands, and the luminescence kinetics of the ²E state can be used for remote pressure readout, with sensitivities of 0.59 nm GPa⁻¹, S_R = 21.7%/Gpa and 12%/Gpa, respectively. Notably, the developed manometer shows the highest sensitivity in the lifetime-based mode reported so far for pressure values above 2 Gpa. Furthermore, the considerable thermal sensitivity of the narrow emission line of Mn⁴⁺ ions (R-line) in the K₂Ge₄O₉:0.1% Mn⁴⁺ material, combined with its minimal shift under pressure for pressures below 1 GPa allows for the utilization of this phosphor as a luminescent sensor capable of concurrently measuring both pressure and temperature.