Herein, luminescence thermal quenching (TQ) of Mn4+-doped fluoride phosphors with a formula A2XF6:Mn4+ (A = K, Na, Rb or Cs; X = Si, Ti, Ge, Sn, Zr or Hf) is overviewed. Some researchers reported that the A2XF6:Mn4+ phosphor showed a normal TQ behavior. On the contrary, numerous researchers claimed that the A2XF6:Mn4+ phosphor showed an anomalous (or negative) TQ behavior, denoting that integrated photoluminescence intensity (I
PL) of a given A2XF6:Mn4+ phosphor increases when the sample temperature rises from a cryogenic- or room-temperature to certain elevated values. Various explanations were proposed for anomalous TQ of Mn4+ luminescence. The creditability of anomalous TQ of Mn4+ luminescence in A2XF6:Mn4+ phosphors and relevant explanations are assessed. It is argued that the anomalous TQ should not be an intrinsic attribute of A2XF6:Mn4+ phosphors. It is suggested that the I
PL enhancement with temperature for A2XF6:Mn4+ phosphors observed by some researchers was likely a pitfall caused by diminishing in optical-path lengths of the spectrofluorometer stemming from lattice thermal expansion. An increase in absorption of the excitation light also contributed to the I
PL enhancement in case that wavelength of blue excitation light used in temperature-dependent spectra measurements corresponds to the low-energy tail of the low-temperature 4
A
2g→4
T
2g excitation band of the A2XF6:Mn4+ phosphor. The credibility of the explanation for the I
PL enhancement with temperature was verified by application to the analysis of a similar anomalous TQ phenomenon reported for the 3.5MgO·0.5MgF2·GeO2:Mn4+ phosphor in literature.
Polyolefins (PO) were melt mixed with thermoplastic polyurethane (TPU) in a 20 : 80 weight ratio with or without compatibilizer containing 0.5 wt % of maleic anhydride. Effects of component viscosities on morphology and on mechanical properties of the blend were studied by scanning electron microscope (SEM), tensile property analysis, and dynamic mechanical analysis (DMA). It was found that the disperse particle size of compatibilizer-free blends decreased with the decreasing viscosity ratio of the disperse phase to TPU. The efficiency of the compatibilizer in reducing the particle size varied with viscosity ratios of the disperse phase to compatibilizer. However, the particle size did not decrease with the decreasing viscosity ratio monotonically. With lower viscosity ratio, addition of 5 wt % compatibilizer resulted in a greater reduction of particle size and less loss in the tensile properties as compared to the TPU matrix. For the polyethene (PE) that has the lowest viscosity value among all the POs, its size in the blend was stabilized with the addition of compatibilizer and no compatibilization was detected by DMA and by tensile property analysis. The mobility of the disperse phase and compatibilizer and the dispersion competition between them seemed important.
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