Enhanced luminescence efficiency and thermal stability via introduction of non-rare earth Bi^(3+)in Gd_5Si_(2)BO_(13):Eu^(3+)

A series of Gd_5Si_(2)BO_(13):Eu^(3+)and non-rare earth Bi^(3+)ions doped Gd_5Si_(2)BO_(13):Eu^(3+)phosphors was successfully synthesized via high-temperature solid-state method,and the as-obtained phosphors were studied on their phase structures,luminescence characteristics,thermal stability and luminescence lifetime.Transient fluorescence spectroscopy data show that the addition of Bi^(3+)can obviously enhance the emission intensity of Eu^(3+)in the near-ultraviolet band owing to energy transfer from Bi^(3+)to Eu^(3+).Besides,the addition of Bi^(3+)can improve the thermal stability of a single-doped phosphor Gd_5Si_(2)BO_(13):0.35Eu^(3+)from 70.33%to 87.45%at 150℃and the quantum yield from 58.80%to 78.61%at room temperature.Finally,Gd_5Si_(2)BO_(13):Eu^(3+),Bi^(3+)was used to encapsulate white light-emitting diodes(WLEDs)with green((Ba,Sr)_(2)SiO_(4):Eu^(2+))and blue(BaMgAI_(10)O_(17):Eu^(2+))commercial phosphors.The color rendering index of WLEDs was calculated to be larger than 90,and the color temperature was estimated to be 4300-4500 K,which demonstrate that Gd_5Si_(2)BO_(13):Eu^(3+),Bi^(3+)can be regarded as a red phosphor with great potential application.This paper can provide a new insight into design of high-efficiency phosphors by introducing non-rare earth Bi^(3+)ions via energy transfer from Bi^(3+)to Eu^(3+).

An optical thermometer with high sensitivity and superior signal discriminability based on dual-emitting Ce^(3+)/Eu^(2+)co-doped La5Si2BO13 thermochromic phosphor

A novel non-contact optical thermometer,qualified with high sensitivity and temperature resolution,is urgently needed for temperature measuring of micro devices,moving objects and specific severe environments.Hence,a series of dual-emitting La_(5)Si_(2)BO_(13):Ce^(3+),Eu^(2+)phosphors were synthesized.The two ions show diverse responses with the changing in temperature.The variational emissions of Ce^(3+)and Eu^(2+)can be converted to FIR(fluorescence intensity ratio)signals.The maximal absolute sensitivity Sa and relative sensitivity Sr reach up to 0.07526%/K and 3.2241%/K,respectively.It is worthy noting that the Sa and Sr possess the same variation tendency and both have high values in the low temperature region(293-373 K),showing the great temperature measuring property especially in low temperature region.The temperature sensing characteristics are superior to the results of most previous reports.The energy transfer(ET)process is certified to occur from Ce^(3+)to Eu^(2+)ions.These studies indicate that La_(5)Si_(2)BO_(13):Ce^(3+),Eu^(2+)phosphor could have a good prospect for optical thermometry.