| Perovskite-type rare-earth manganese oxide is a set of single-phase multiferroic materials with ferromagnetism and antiferromagnetism, as one of the representatives, YMnO3 is an emerging giant magnetoresistance and magnetic composite material system, which attracks extensive attention by the academia. YMnO3 is one of Perovskite materials with wide application in various fields such as high performance pigment, magnetic material, optical material and catalysis, etc. In this paper, single-phase nanocrystalline YMnO3 and Fe3+doped complex oxides has been synthesized by a modified polyacrylamide gel route, TG-DTA, FTIR, XRD, Laser Particle Distribution Analyzer, TEM, Uv-Vis Spectrometer, Uv-Vis-NIR Spectrometer and Color-Eye 7000A Spectrophotometer were applied to characterize the thermo-performance and the composition of the precursors, structure, morphology, particle size distribution, Uv-Vis absorbance curve, the infrared reflection property and the color parameters of the sample, respectively.In the modified polyacrylamide gel route method, the impact of different reductant/oxidant ratio (CA/NO3-), calcination program, water bath temperature, molar ratio of aggregation agents (acrylamide and N-N'dimethyl acrylamide) and different pH on the thermo performance of the precursor, lattice distortion ratio, morphology, color, gel formation time, the infrared reflection properties and the absorbtion curve were studied. The lattice distortion and crystalline size of the samples prepared by different calcination rates and water bath temperature were estimated by Scherrer method. YMnO3 was also treated as a host to accept Fe3+. The structure and Uv-Vis-NIR performance of the complex oxides were investigated, associated with phase structure and electronic structure of YMnO3, the infrared reflection mechanism was also made a preliminary study, too.Results show that M (CA/NO3-)=1.5 exhibits the best thermo reaction performance, single phased and uniform yttrium manganese oxide can be obtained by igniting the precursor at 400℃and then soaking at 900℃for 10h. Gel can be formed in the water bath at 80～85℃for 2.5h. Adjust the pH to 2 is suitable to gain single-phased samples with high crystallinity. Three absorbtion bands at about 423,500 and 598cm-1 were witnessed in IR spectrum, which were ascribed to the bending vibration absorption of Mn-O-M,the stretching vibration absorption of Y-0 and the stretching vibration absorption of Mn-O, respectively. The main absorbtion bands at about 650-700nm can be seen in the Uv-Vis curve, the pigment exhibits deep blue black in colour, As the increase of the calcination temperature, the absorbance decreases slightly and the absorption of visible light corresponds a slight red shift due to the spin allowed transition of O2p-Mn4d. As shown in UV-Visible-NIR curve. YMnO3 nanoparticles fabricated by the modified polyacrylamide gel route were proved to own a high infrared reflectivity (about 50%), owing to the narrow band gap (2.18eV), small particle size (40-60nm) and high specific surface area, it can be used as "'cool"pigment to replace conventional toxic and low performancepaints. what is more, the high infrared reflectance of YMnO3 pigment comes to the spin allowed d-d transition or the electron charge transfer of Mn3+(4d) and O2-(2p). For this part, a deeper system study is still in progress. Fe3+ doped complex oxides were found to have better infrared reflectance performance without change in structure, which can be attributed to the increase of crystal defects and Impurities, leading the change of particle size distribution and the electronic environment. |
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