Contactless thermometer based on fluorescence intensity ratio shows unparalleled characteristics compared with traditional contact thermometers. However, few materials are suitable for high temperature (above 573 K) measurement. In this work, Pr 3+ was selected as the emitter and Y 3 GaO 6 :xPr 3+ luminescent thermometers were designed. The phase, crystal structure and morphology were identified using X-ray diffraction, Rietveld refinement and scanning electron microscope. The spectra with multiple ranges were temperature sensitive due to the cross-relaxion mechanism that occurs in the luminescence process. The parameters for temperature measurement were determined based on the peak intensity ratio of 506 and 610 nm at different temperatures (from 293 to 823 K). Y 3 GaO 6 :0.01Pr 3+ displays excellent temperature sensitive performance, in which the relative sensitivity values increase along with the temperature in a wide temperature range and reach 4.09 % K −1 . The thermometric visualization in Y 3 GaO 6 :xPr 3+ can be achieved due to the widely varying luminescence colors at different temperatures.
High density negative temperature coefficient (NTC) thermistor ceramics Bi 0.2-x Ce x Sr 0.5 La 0.3 TiO 3 (0 < x < 0.05) (BCSLTO) were synthesized by the Pechini method. This work is the first to characterization analysis the excellent NTC characteristics of BCSLTO ceramics at high temperatures. BCSLTO NTC thermistor ceramics have wide operating temperature is 300 °C-1000 °C, and mild sintering conditions with the conventional sintering at 1250 °C. The important electrical performance parameters of BCSLTO ceramics are as follows: the resistivities at 300 °C, 700 °C, and 1000 °C are 3.26 × 10 9 –8.99 × 10 7 Ω cm, 2.21 × 10 5 –1.05 × 10 5 Ω cm, and 1.18 × 10 3 –1.13 × 10 3 Ω cm, respectively; the thermal constant B 300/700 is 13385.9–9408.8 K; the activity energy Ea 300/700 is 1.15–0.81 eV. The resistivity and the thermal constant B can be widely control by doping Ce. In addition, the resistivity drift improves as the Ce doping content increases (below 5%). The new high-temperature Bi 0.2-x Ce x Sr 0.5 La 0.3 TiO 3 ceramic materials with mild sintering conditions, wide operating temperature and high-temperature stability can be used as potential candidates for high temperatures and harsh environments.
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