Study On Preparation Of Oxide-based Upconversion Luminescent Materials And Their Temperature Sensing Property

The measurement of temperature is closely related to scientific research,industrial production and daily life of human beings.So far,researchers are of great concern about the optical temperature sensing materials which use the fluorescence intensity ratio technique?FIR?to measure the temperature.FIR technique based on the thermally coupled levels of rare earth ions has been regarded as a very promising approach for non-contact optical temperature sensing.Compared with the measurement for absolute fluorescence intensity and luminescence lifetime,FIR method can effectively avoid the error caused by the fluorescence loss and the number of the luminescence center in the detection.In this thesis,the up-conversion luminescence?UCL?,temperature sensing behavior and electrical properties in Er³⁺ions doping and Er³⁺/Yb³⁺ions codoping ferroelectrics and tungstate materials were investigated.The main achievements are described as follows:?1?For the Er³⁺ions doped Bi₃Ti_1.5WO₉ ceramics,by changing the doping concentration of Er³⁺ions,the color could be tunable from green to yellow.The electrical and UCL properties were enhanced by introducing a small amount of Er³⁺ions.For Er³⁺/Yb³⁺ions codoped Bi₃Ti_1.5WO₉ ceramics,the emitted light was highly saturated.In addition,by using the FIR technique,the sensitivity had a large improvement of 33%by codoping 0.09 mol Yb³⁺in BTW:0.03Er at 483 K.Besides,by introducing La³⁺ions to replace the Bi³⁺in the A-sites of BTW:0.03Er,0.09Yb,the ferroelectric properties and dielectric properties were enhanced and the Curie temperature was effectively reduced.What's more,by introducing Nb⁵⁺ions to replace the Ti⁴⁺and W⁶⁺in the B-sites of BTW:0.03Er,0.09Yb,the UCL and ferroelectric properties could be improved.When the concentration of Nb⁵⁺ions was 4mol%,a large remnant polarization P_r?17.7?C/cm²?and a small coercive field?147.5kV/cm?were obtained.?2?Er³⁺-doped and Er³⁺/Yb³⁺-co-doped xLiNbO₃-?1-x??K,Na?Nb O₃?xLN-?1-x?KNN?ferroelectric ceramics were synthesized by a solid state reaction process.It found that UCL intensity was effectively controlled by altering the polarization time under an external electric field of 2 kV/mm.Furthermore,an optimal UCL was observed in a 0.4LN-0.6KNN:Er³⁺,3Yb³⁺sample and its excellent optical temperature sensitivity(0.006 K^-1 at 643 K)from 83 to 663 K was 131%higher than that of 0.4LN-0.6KNN:Er³⁺.?3?On the basis of the idea of material design,several tungstate multiphase materials have been prepared,such as strontium tungstate?SWO?,calcium lanthanum tungstate(La_2xCa_3?1-x??WO₄?₃)and yttrium potassium tungstate?x KYW-?1-x?KW?.According to the samples'structures and UCL features,Er-doped strontium tungstate?SWOE-x?phosphors with multiphase structure were divided into three sorts,Sr₃WO₆types,Sr₂WO₅ types,and SrWO₄ types.The influence of the Sr/W ratio in Er-doped strontium tungstates on temperature sensing property has been investigated via the fluorescence intensity ratio?FIR?technique.The maximal S is determined to be0.01275 K^-1 at 523K with a broad temperature range from 83K to 563K in SWOE-0.6.For Er³⁺/Yb³⁺codoped La_2xCa_3?1-x??WO₄?₃ multiphase materials,the UCL intensity of multiphase materials was higher than that of pure phase?CaWO₄ and La₂?WO₄?₃?based luminescent materials.Besides,the temperature sensing properties of multiphase materials were still excellent in a broader temperature range.For Er³⁺/Yb³⁺codoped xKY?WO₄?₂-?1-x?K₂WO₄ multiphase materials,the UCL intensity of multiphase materials luminescent materials was higher than that of pure phase based luminescent materials.Besides,an optimal UCL was observed in the 0.6KYW-0.4KW sample.The maximal S is determined to be 0.0147 K^-1 at 643K with a broad temperature range from83K to 663K in 0.6KYW-0.4KW.