STUDY ON THE STRUCTURE AND PROPERTIES OF SEMICONDUCTOR CERAMIC COOLING MATERIALS

In this paper, thermoelectric polycrystal ceramic materials were prepared by a new ceramic technology. The p-type 72% Sb2Te3+ 25%Bi2Te3 + 3%Sb2Se3 doped with Te and 90%Bi2Te3 + 5%Sb2Te3 + 5%Sb2Se3 doped with SbI3 or AgI samples were studied. The new ceramic cooling materials have an inhomo-geneous structure, higher mechanical strength and the thermoelectric properties. With the help of phase diagrams, Differantial Thermal Analysis, X-Ray diffractograms, the observation of high temperature microscope and the relation between technology conditions and thermoelectric properties were obtained in optimum technology conditions. Measurements of properties show that the sintering temperature and time have an effect on the thermoelectric properties of the samples. Scan electronic microscope shows that the polycrystal ceramic materical has an obvious layered structure. Electrical probe microscope analysis indicates that the mol contents of Bi, Te,Sb and Se which compose samples are re- spectively comsistent with original compositions. The distribution of these elements in the samples is well uniform. Doping materials has been studied including doping variety and doping concentration. The figure of merit of n-type doped SbI3 is 2.9 × 10-3 1/k. The figure of merit of p-type doped Te is 3. 1 ×10-3 1/ K.

High-entropy rare earth stannate ceramics:Acid corrosion resistant radiative cooling materials with high atmospheric transparency window emissivity and high near-infrared solar reflectivity

In response to the development of the concepts of“carbon neutrality”and“carbon peak”,it is critical to developing materials with high near-infrared(NIR)solar reflectivity and high emissivity in the atmospheric transparency window(ATW;8–13μm)to advance zero energy consumption radiative cooling technology.To regulate emission and reflection properties,a series of high-entropy rare earth stannate ceramics(HE-RE_(2)Sn_(2)O_(7):(Y_(0.2)La_(0.2)Nd_(0.2)Eu_(0.2)Gd_(0.2))_(2)Sn_(2)O_(7),(Y_(0.2)La_(0.2)Sm_(0.2)Eu_(0.2)Lu_(0.2))_(2)Sn_(2)O_(7),and(Y_(0.2)La_(0.2)Gd_(0.2)Yb_(0.2)Lu_(0.2))_(2)Sn_(2)O_(7))with severe lattice distortion were prepared using a solid phase reaction followed by a pressureless sintering method for the first time.Lattice distortion is accomplished by introducing rare earth elements with different cation radii and mass.The as-synthesized HE-RE_(2)Sn_(2)O_(7)ceramics possess high ATW emissivity(91.38%–95.41%),high NIR solar reflectivity(92.74%–97.62%),low thermal conductivity(1.080–1.619 W·m^(−1)·K^(−1)),and excellent chemical stability.On the one hand,the lattice distortion intensifies the asymmetry of the structural unit to cause a notable alteration in the electric dipole moment,ultimately enlarging the ATW emissivity.On the other hand,by selecting difficult excitation elements,HE-RE_(2)Sn_(2)O_(7),which has a wide band gap(Eg),exhibits high NIR solar reflectivity.Hence,the multi-component design can effectively enhance radiative cooling ability of HE-RE_(2)Sn_(2)O_(7)and provide a novel strategy for developing radiative cooling materials.

The effects of cool materials,façade orientation,and morphological parameters on energy consumption at the residential neighborhood scale

Building surface cool materials are novel materials that can reduce urban heat island intensity and decrease building energy consumption.This study investigated the impact of radiative properties of materials,façade orientation,and morphological parameters on energy consumption in six typical residential neighborhoods in Nanjing,China.The neighborhood energy consumption of 16 application schemes considering the façade orientation factor is compared to determine the best energy-saving scheme.Seasonal and annual energy-saving rates,savings in electricity costs,and the price ceiling for materials per unit area are analyzed.The results show that for low-rise buildings,using cool materials only on the roof can reduce the annual energy consumption by 1%.When cool or super cool materials are also used on the building façade,the annual energy saving rate can be up to 3.4%and 4.3%,respectively.Using cool materials on the south façade of buildings is not recommended due to significant heat loss in winter.Considering savings in electricity costs and the price ceiling for materials per unit area,the price of cool and super cool materials should be less than 3.0 and 3.7 RMB/m2,respectively,assuming a lifespan of eight years in Nanjing.