Compositional variation of photoluminescence from Mn doped MgAl2O4 spinel

•1% Mn doped MgAl2O4 are grown from various compositions in 50% O2–Ar gas.•PL peaking at 520 nm and 750 nm are observed from crystals.•Peak wavelength of PL increases linearly from 512 to 520 nm with composition.•Intensities and thermal activation energy of PL vary with crystal composition.

Spinel (MgAl2O4) crystals doped with 1.0% Mn have been grown by floating zone (FZ) technique with various Mg compositions, x = MgO/Al2O3, from 0.2 to 1.0. Compositional variations of photoluminescence are evaluated for a fluorescence thermometer application using crystals grown. Strong photoluminescence (PL) peak is observed at λ from 512 to 520 nm from the crystals grown from compositions, x, from 0.3 to 1.0. Peak wavelength of PL increases linearly from 512 to 520 nm with x. Weak PL peaking at λ = 750 nm is also observed from the specimens. Compositional variations of PL are considered to be due to the variation of crystal field surrounding the Mn2+ ions. The variation of crystal field strength agrees with the compositional variation of lattice constant.