Pressure-mediated structural evolution and luminescent properties of MgGeO3:Mn2+ nanoparticles: a new candidate for optical high-pressure sensors

Abstract

A nanosized near-infrared (NIR)-emitting phosphor, Mn²⁺-doped MgGeO₃ (MGO:Mn), was found to exhibit remarkable pressure-dependent color-changing properties over a broad pressure range. The emitting center, Mn²⁺, when excited with 360 nm UV radiation, emits NIR light at 675 nm under ambient conditions, originating from the ⁴T₁ → ⁶A₁ d–d transition. During compression, this emission exhibits a prominent red shift at a rate of 5.43 nm GPa⁻¹ until the applied pressure reaches 10.5 GPa. The correlation between the structure and luminescent properties of MGO:Mn under the influence of applied pressure was thoroughly investigated using in situ characterization methods, including Raman spectroscopy, X-ray diffraction, and photoluminescence spectroscopy. A partially reversible phase transformation of the MgGeO₃ from Pbca to C2/c was observed, which was responsible for the change in the crystal field strength surrounding Mn²⁺. These findings demonstrate that MGO:Mn is a promising candidate for a non-contact luminescence-based manometer in high pressure applications.