For practical applications, the stability of perovskite-like oxides in various environments should be evaluated. In this work, samples of Gd0.8Ca0.2BaCo2O5+δ (GCBC2)were annealed in different atmospheres and at different temperatures, and changes in their spectral reflective properties, infrared radiative properties, and electrical conductivity properties under solar irradiation were investigated using thermogravimetric analyses, reflection spectra measurements, electrical conductivity measurements, and X-ray photoelectron spectroscopy. The results of the study show that oxygen non-stoichiometry is dependent on the temperature and atmosphere used during the annealing process. In an oxygen atmosphere, an increase in oxygen non-stoichiometry was observed up to temperatures of 500 °C, and then a decrease at 800 °C. In a nitrogen atmosphere, oxygen stoichiometry always decreased at temperature above 400 °C. Although an increase in oxygen content had no effect on the ceramic’s electrical and optical properties, a decrease in oxygen content affected its properties significantly. Therefore, because GCBC2 has a typical insulator–metal transition under solar irradiation below 500 °C, and a low infrared emissivity in oxidized atmospheres, it can be used as a solar thermal conversion material, or for spacecraft thermal control devices in an oxidized environment.

•Sm0.5Sr0.5CoO3-δ ceramic was modified with CuO by magnetron sputtering and subsequent annealing treatments.•Surface morphologies and spectra properties were adjusted by the temperatures and atmospheres of annealing treatments.•Modified Sm0.5Sr0.5CoO3-δ annealed at 400 °C in an oxygen atmosphere for 1 h exhibits a high solar selectivity of 2.58.We investigated the optical properties of CuO-modified Sm0.5Sr0.5CoO3-δ ceramics as possible candidate materials for solar absorbing applications. Bulk composite materials were successfully prepared by a facile and cost-effective solid-state reaction method and subsequent magnetron sputtering. The solar absorbance and spectral selectivity properties were evaluated using room-temperature hemispherical reflectance spectra measured from the ultraviolet to the mid-infrared region for samples with different composition, thickness, and surface roughness. The effect of annealing at different temperatures in air or oxygen was also investigated. The experimental results showed that a composite of Sm0.5Sr0.5CoO3 and Cu (100 nm) ceramic annealed at 600 °C in air for 1 h had a solar absorbance comparable to that of the most advanced solar absorber materials, such as silicon carbide, with a higher spectral selectivity. Our material also exhibits better solar-selective absorption properties and higher solar selectivity (2.69) than that of smooth, unmodified Sm0.5Sr0.5CoO3 (2.07) and could potentially be used as an alternative material for spectrally selective absorber applications.Download high-res image (139KB)Download full-size image

•The optical properties of La1−xSrxCoO3−δ (0.2 ⩽ x ⩽ 0.8) ceramics were studied.•The investigated samples showed low thermal emittance at high temperatures.•La0.5Sr0.5CoO3−δ solar absorber was thermally stable in air up to 800 °C for 10 cycles (90 h).Perovskite-type La1−xSrxCoO3−δ (0.2 ⩽ x ⩽ 0.8) ceramics were prepared by tape casting and solid state reaction method. The room temperature optical properties of these samples were studied in detail. The temperature dependent emittance measurements and high-temperature durability tests were carried out. Results showed that these materials exhibited low reflectance at the solar spectrum wavelengths and high reflectance in the infrared region, with an optimal spectral selectivity of 3.2. The investigated samples showed low thermal emittance at high temperatures. More importantly, the sample was highly stable in air at 800 °C, as the performance criterion value was lower than 0.05 after 10 cycles (90 h) heat treatment. Our results demonstrate that the La1−xSrxCoO3−δ ceramics have the potential to emerge as high temperature (∼800 °C) solar absorbers for the future solar power systems.

•The solar absorption properties of GdBaCo2O5+δ can be improved by Ca doping.•Gd0.8Ca0.2BaCo2O5 shows ultrafast conductivity transition induced by solar energy.•Gd0.8Ca0.2BaCo2O5 exhibits low thermal radiative properties at high temperature.This study reveals that the use of a Ca dopant can increase the solar absorption of GdBaCo2O5+δ, with an optimal composition of Gd0.8Ca0.2BaCo2O5 achieving 85% solar absorptance. Electrical conductivity measurements revealed that this composition allows for faster insulator-metal transition and higher conductivity, with the observed variation in conductivity with 0.8 W/cm2 of solar illumination explained in terms of a first-order spin-state transition. Thermal radiation imaging confirmed that regions of different radiative temperature are related to a change in free carriers that promote scattering, and therefore, cause an increase in infrared reflection. This rapid electrical conductivity transition and the low infrared radiation properties at high temperatures strongly suggest that Gd0.8Ca0.2BaCo2O5 could be used in a variety of potential fields, such as high-temperature thermosensitive or thermal storage materials.

•Spectrally selective absorbing properties of Ti3SiC2 and Zr3[Al(Si)]4C6 are investigated.•The spectral selectivity of Ti3SiC2 and Zr3[Al(Si)]4C6 are 3.7 and 2.8, respectively.•Ti3SiC2 and Zr3[Al(Si)]4C6 exhibit a low emissivity in the investigated temperature range.•Suitability of Ti3SiC2 and Zr3[Al(Si)]4C6 as high-temperature solar absorbers is discussed.Layered Ti3SiC2 and Zr3[Al(Si)]4C6 ceramics were prepared by hot-pressed sintering. The spectrally selective absorption properties of these layered carbides have been investigated and compared with those of TiC and ZrC. It is found that the Ti3SiC2 ceramic exhibits a solar absorbance of 0.70 and a thermal emissivity of 0.19, yielding spectral selectivity (absorbance divide by emissivity) of 3.7, while the spectral selectivity of Zr3[Al(Si)]4C6 is 2.8 (0.71/0.25). To evaluate the suitability of these ceramics as high-temperature absorbers for solar radiation, the investigation on the thermal stability and temperature dependent emittance was performed in air. Compared with TiC and ZrC, both Ti3SiC2 and Zr3[Al(Si)]4C6 show better thermal stability. Meanwhile, Ti3SiC2 and Zr3[Al(Si)]4C6 exhibit a low emissivity in the investigated temperature range, benefiting from their metal-like electrical conductivity.

Calcium-doped lanthanum chromite, La1−xCaxCrO3, was prepared using a solid-state reaction method, and the effect of varying the Ca content (0 ≤ x ≤ 0.5) was investigated in relation to its crystalline structure, surface morphology, solar absorption and thermal radiation. This found that the crystalline structure is slightly distorted by Ca2+ doping, with an accompanying increase in the valence state of Cr ions and oxygen vacancies enhancing both the solar absorption and thermal emittance. Overall, the La1−xCaxCrO3 system displays relatively high thermal radiation properties, with an optimal composition of La0.5Ca0.5CrO3 exhibiting a solar absorption of 95% and a thermal emittance of 0.94. When used as a light absorber coupled to a thermoelectric module this proved capable of generating electricity and hot water, thereby demonstrating the suitability of this energy-saving material for use in solar thermal radiation applications.

Surface textured Sm0.5Sr0.5CoO3−δ oxide ceramics were prepared by means of compression molding followed by high temperature sintering. The effects of surface texture on the optical and photo-thermal conversion performances of Sm0.5Sr0.5CoO3−δ were investigated. Results showed that the solar absorptance of Sm0.5Sr0.5CoO3−δ increased from 0.69 to 0.85 because of surface texturization. Besides, textured Sm0.5Sr0.5CoO3−δ exhibited better photo-thermal conversion ability than the planar ones, with almost no selectivity to the incident irradiation, normal or oblique. Optimized samples were tested as sunlight absorber for concentrating solar thermoelectric generator. It is anticipated that the textured Sm0.5Sr0.5CoO3−δ ceramic absorber can be extended to design non-tracking concentrating solar thermoelectric generators.

•Study on mechanical and thermal properties of cement-based thermal storage material.•The effect of fly ash on thermal properties of aluminate cement paste.•Find the ratio of cement/fly ash to obtain optimum properties of composite paste.In this paper, we investigate mechanical and thermal properties of aluminate cementitious thermal energy storage material with fly ash. According to the specific requirement of application of thermal storage materials in solar thermal power generation, we selected 350 °C and 900 °C as the heat treatment temperatures. It can be seen that after heat treatment, the compressive strength and porosity of the cementitious materials are both optimized with the optimal fly ash amount of 15 wt%. Moreover, thermal conductivity and volume heat capacity of the composite pastes incorporated with fly ash are enhanced as well, which is more suitable for the application in solar energy storage. The microstructure, the evaluation of hydration products, and the pore distribution were obtained by SEM, XRD and MIP, respectively.

A new type of inner-motile photocatalyst film is explored to enhance photocatalytic performance using magnetically actuated artificial cilia. The inner-motile photocatalyst film is capable of generating flow and mixing on the microscale because it produces a motion similar to that of natural cilia when it is subjected to a rotational magnetic field. Compared with traditional photocatalyst films, the inner-motile photocatalyst film exhibits the unique ability of microfluidic manipulation. It uses an impactful and self-contained design to accelerate interior mass transfer and desorption of degradation species. Moreover, the special cilia-like structures increase the surface area and light absorption. Consequently, the photocatalytic activity of the inner-motile photocatalyst film is dramatically improved to approximately 3.0 times that of the traditional planar film. The inner-motile photocatalyst film also exhibits high photocatalytic durability and can be reused several times with ease. Furthermore, this feasible yet versatile platform can be extended to other photocatalyst systems, such as TiO2, P25, ZnO, and Co3O4 systems, to improve their photocatalytic performance.

•Sm0.5Sr0.5Co1−xCrxO3 can be used as a controlled near-infrared reflective inorganic oxide.•Sm0.5Sr0.5Co1−xCrxO3 was prepared by solid-state reaction.•Effects of Cr3+ doping on crystal structure and electrical conductivity were found.•Solar absorbance, infrared emittance can be controlled by Cr3+ dopant concentration to meet various demands.A new application of Sm0.5Sr0.5Co1−xCrxO3 as a controlled near-infrared reflective inorganic oxide has been developed. Samples were prepared by a solid-state reaction to form a perovskite solid solution with an orthorhombic structure. Then, the effect of Cr3+ cation doping on the crystal structure, electrical conductivity, solar absorbance, and thermal emittance properties of the Sm0.5Sr0.5Co1−xCrxO3 was investigated. The electrical conductivity decreases upon the substitution of Cr3+ ions for Co3+/Co4+ because of the appearance of Cr3+–O2−–Cr3+ and Co3+–O2−–Cr3+ units, reducing the amount of the Co3+–O–Co4+ network. The Cr3+ ions doped into Co3+ sites were found to enhance the solar absorbance from 68.2% to 91.6% and to simultaneously increase the infrared emittance from 0.25 to 0.93. The mobility of infrared optical phonons from free electrons decreases upon Cr3+ doping, which weakens the scattering effect and enhances the absorption. Based on these properties, we can control the Cr3+ dopant concentration of Sm0.5Sr0.5Co1−xCrxO3 to meet our demands.

•Designed classical complexes have been synthesized to compare their stability.•Substitutes on ligands play a crucial role on the stability of the complexes.•p-Fluorobenzoicacid works well as a superior thermal stability ligand.•[Sm(p-FBA)3Phen]2 complex can well serve as a thermally stable phosphor.Three kinds of Sm(L)3Phen⋅nH2O complexes (L: α-thenoyltrifluoroacetone (HTTA), 4-fluorobenzoicacid (p-FBA) and 4-aminobenzoicacid (p-ABA)) were designed and synthesized by the wet chemical method. Their thermal stabilities were compared through thermogravimetric analysis (TGA) and high temperature photoluminescence measurements. The results indicated that [Sm(p-FBA)3Phen]2 presented the best thermal stability, and the photoluminescence intensity could remain 50% even after being heat-treated at 280 °C for 20 min. Not only the rigidity of the organic ligand and complexes structures, but also the coordinating ability between rare earth ions and ligand played a crucial role in the stability of the complexes. In this article, p-fluorobenzoicacid has been proven to be a promising ligand for the preparation of highly luminescent and stable rare earth complexes.Graphical abstract

•Spectrally selective absorbing properties of Ti3SiC2 and Zr3[Al(Si)]4C6 are investigated.•The spectral selectivity of Ti3SiC2 and Zr3[Al(Si)]4C6 are 3.7 and 2.8, respectively.•Ti3SiC2 and Zr3[Al(Si)]4C6 exhibit a low emissivity in the investigated temperature range.•Suitability of Ti3SiC2 and Zr3[Al(Si)]4C6 as high-temperature solar absorbers is discussed.Layered Ti3SiC2 and Zr3[Al(Si)]4C6 ceramics were prepared by hot-pressed sintering. The spectrally selective absorption properties of these layered carbides have been investigated and compared with those of TiC and ZrC. It is found that the Ti3SiC2 ceramic exhibits a solar absorbance of 0.70 and a thermal emissivity of 0.19, yielding spectral selectivity (absorbance divide by emissivity) of 3.7, while the spectral selectivity of Zr3[Al(Si)]4C6 is 2.8 (0.71/0.25). To evaluate the suitability of these ceramics as high-temperature absorbers for solar radiation, the investigation on the thermal stability and temperature dependent emittance was performed in air. Compared with TiC and ZrC, both Ti3SiC2 and Zr3[Al(Si)]4C6 show better thermal stability. Meanwhile, Ti3SiC2 and Zr3[Al(Si)]4C6 exhibit a low emissivity in the investigated temperature range, benefiting from their metal-like electrical conductivity.

Cobalt-based perovskite oxides, LnBaCo2O5+δ (Ln=La to Lu), were investigated as potential variable electrical and thermal radiative materials under solar irradiation. The particular Ln3+ dopant has a significant effect on the oxide's phase structure, spectral reflectivity, electrical conductivity, and thermal radiative properties. Stable, cation-ordered oxides with layered lattice structures were obtained with medium-size Ln3+ ions. The general features of the electrical and spectral reflective properties of LnBaCo2O5+δ (Ln=La, Nd, Sm to Ho) are discussed. It is shown that LnBaCo2O5+δ (Ln=Sm to Ho) has a significant insulator–metal transition under solar irradiation, whereas LnBaCo2O5+δ (Ln=La, Nd) has a lower infrared emissivity at high temperatures due to the metal-like optical behavior.