A new ratiometric Boltzmann thermometry approach is presented for the narrow-line red-emitting bright phosphor Al_(0.993)Cr_(0.007)B_(4O6)N.It relies on thermalization between the two excited states^(2)E_(g)(^(2)G)and...A new ratiometric Boltzmann thermometry approach is presented for the narrow-line red-emitting bright phosphor Al_(0.993)Cr_(0.007)B_(4O6)N.It relies on thermalization between the two excited states^(2)E_(g)(^(2)G)and^(2)T_(1g)(^(2)G)of Cr^(3+)with an energy gap of 620 cm^(−1)for optimized thermometry at room temperature.It is shown that nonradiative coupling between these excited states is very fast,with rates in the order of severalµs^(−1).Due to the comparably slow radiative decay(k_(r)=0.033 ms^(−1))of the lowest excited^(2)E_(g)(^(2)G)state,the dynamic working range of this Boltzmann thermometer for the deep red spectral range is exceptionally wide,between<77 K and>873 K,even outperforming the classic workhorse example of Er^(3+).At temperatures above 340 K,also spectrally well-resolved broad-band emission due to the spin-allowed^(4)T_(2g)(^(4)F)→^(4)A_(2g)(^(4)F)transition is detectable,which simultaneously offers a possibility of very sensitive(S_(r)(500 K)>2%K^(−1))ratiometric Boltzmann-type crossover thermometry for higher temperatures.These findings imply that Al_(0.993)Cr_(0.007)B_(4)O_(6)N is a particularly robust and bright red luminescent thermometer with a record-breaking dynamic working range for a luminescent transition metal ion.展开更多
基金support by the“Young College”of the North-Rhine Westphalian Academy of Science,Humanities,and the Arts.Generous funding by the German National Science Foundation(DFG,SU 1156/5-1,project no.554302036)and the Strategic Research Fund of the HHU Düsseldorf is also gratefully acknowledged.
文摘A new ratiometric Boltzmann thermometry approach is presented for the narrow-line red-emitting bright phosphor Al_(0.993)Cr_(0.007)B_(4O6)N.It relies on thermalization between the two excited states^(2)E_(g)(^(2)G)and^(2)T_(1g)(^(2)G)of Cr^(3+)with an energy gap of 620 cm^(−1)for optimized thermometry at room temperature.It is shown that nonradiative coupling between these excited states is very fast,with rates in the order of severalµs^(−1).Due to the comparably slow radiative decay(k_(r)=0.033 ms^(−1))of the lowest excited^(2)E_(g)(^(2)G)state,the dynamic working range of this Boltzmann thermometer for the deep red spectral range is exceptionally wide,between<77 K and>873 K,even outperforming the classic workhorse example of Er^(3+).At temperatures above 340 K,also spectrally well-resolved broad-band emission due to the spin-allowed^(4)T_(2g)(^(4)F)→^(4)A_(2g)(^(4)F)transition is detectable,which simultaneously offers a possibility of very sensitive(S_(r)(500 K)>2%K^(−1))ratiometric Boltzmann-type crossover thermometry for higher temperatures.These findings imply that Al_(0.993)Cr_(0.007)B_(4)O_(6)N is a particularly robust and bright red luminescent thermometer with a record-breaking dynamic working range for a luminescent transition metal ion.
