Detailed investigations of the photoluminescence properties of Mn4+ (3d3) ions in YAlO3 have been performed in the temperature range 10–600 K. The luminescence of Mn4+ ions due to the transition consists of two zero-phonon lines (R lines) at 691.3 and 692.7 nm, which became visible only at low temperature, and their vibronic sidebands that cover the range of 660–740 nm. The thermal quenching of the luminescence intensity due to the non-radiative decay occurs at temperatures above 420 K. The temperature dependence of the luminescence decay time shows a quasi-linear decrease from τ = 4.9 to 1.6 ms in the temperature range from 90 to 420 K (with a temperature coefficient −0.01 ms K−1) that makes YAlO3:Mn a potentially good phosphor for a fibre optic fluorescence thermometer in this temperature range. The high-pressure low-temperature luminescence measurements in a diamond-anvil cell reveal similar pressure coefficients for Mn4+ and Cr3+ dopant ions in YAlO3, equal to 1.16 cm−1 kbar−1 and 1.08 cm−1 kbar−1, respectively.

We present results of a high-pressure photoluminescence study of Mn-and Ca-doped gadolinium gallium garnet (GGG) crystals. Since the Mn 4+ ion has the same electronic structure of the open 3d 3 shell as Cr 3+ , its spectroscopic properties are expected to be similar to those of the Cr-doped GGG. We observed the luminescence R-lines of various Mn 4+ centres in GGG. In the 0-118 kbar pressure range those R-lines shift linearly to lower energies. The pressure coefficients are of the order of 2 cm −1 kbar −1 , about three times larger than that for Cr 3+ ions. This fact can be explained by different strength of coupling of isoelectronic Cr 3+ and Mn 4+ ions with GGG host. The changes of the radiative decay times of the Mn 4+ centres as a function of pressure are fitted with a theoretical model.

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Pressure-induced shift of various luminescence lines of Nd3+-doped yttrium aluminum garnet crystal in the pressure range of 0–120kbars and temperatures between 10 and 300K is reported. Spectral positions of all these lines in the region of 900–960nm shift linearly towards lower energies with the pressure coefficient values from −0.01to−0.99cm−1∕kbar in the examined pressure range. Two of these lines have similar pressure coefficients than those of the R lines of Cr3+ in ruby. Therefore, they can be readily used for pressure calibration in diamond anvil cells.