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.
Single crystals of fi-Gaz-LIn,03 with z = 0 to 0.2 have been grown by the float zone technique using radiation heating. When z increases from 0 to 0.2, the interionic distance 0-Ga in the gallium octahedron and tetrahedron increase on the average by l to 1.5% and, as a consequence, the position of the steep absorption edge of hand-to-hand electron transitions shifts towards smaller energies by 0.3 eV. Simultaneously, a strong and broad absorption band in the energy range 3.5 to 4.5 eV appears, caused by charge transfer electron transitions from 2p oxygen to 5s indium energy levels in octahedral indium clusters.
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