| Sm2(Zr1xTix)2O7and Sm2(Zr1xMnx)2O7ceramics doped with different contentswere successfully prepared at1600oC and1700oC respectively, by a solid state reactionprocess, as well as the rare earth ions(Nd3+, Gd3+, Yb3+and Ce3+) doped samariumzirconate ceramics with the doping content of10%for comparative tests. X-raydiffraction (XRD), scaning electron microscopy (SEM) and X-ray energy dispersivespectroscopy (EDS) were used to characterize the phase structure and microstructure ofvarious doped system samarium zirconate ceramics. The thermal properties of differentzirconate ceramics were characterized by the normal spectral emissivity based on amethod of radiant energy comparison. Sm2Zr2O7, Sm2(Zr0.85Ti0.15)2O7andSm2(Zr0.9Mn0.1)2O7ceramics were selected for Fourier transform infrared spectroscopyand UV-Visible-NIR absorption spectroscopy tests for explaining the thermal radiativemechanisms of doping transition metal ions to enhance the samarium zirconate thermalradiation performance.XRD diffraction analysis of samarium zirconate ceramics sintered at1600oC and1700oC for10hours showed that the sintering temperature has no affect on their phasestructure, and their main phase is pyrochlore. The microstructure morphology of thesamples obtained at the same identical sintering temperature is basically the same?theirgrain growth was in good condition, some samples have the relative density of above95%. There exists a linear relationship between the lattice parameter a ofSm2(Zr1xTix)2O7ceramics changes with increasing Ti4+doping content, so the solidsolubility limit of Ti4+ion should be larger than0.15in the samarium zirconate ceramics.As for Sm2(Zr1xMnx)2O7, the solid solubility of Mn4+ions in samarium zirconate isnot high, when the Mn4+ions doping content reaches10%will generate a second phase,which was confirmed by XRD and EDS to be SmMnO3, that means no solutiondescribed Mn4+ions into the crystal lattice of samarium zirconate any more, the solidsolubility limit of Mn4+ions in samarium should be between0.05and0.1The doped samarium zirconate normal spectral emissivity measurement data showsthat the effect of sintering temperature on the thermal radiation properties of samariumzirconate ceramics mainly concentrates in the short wavelength(3~7m), the thermalradiation properties of samples sintered at1700oC are slightly better. Different rare earth ions(Nd3+, Gd3+, Yb3+and Ce3+) and transition metal ions(Ti4+, Mn4+) doping canenhance samarium zirconate thermal radiation properties, the effect of doping of rareearth on the samarium zirconate radiation properties is very small, however, the dopingof transition metal Ti4+and Mn4+ions can obviously enhance the samarium zirconatethermal radiation properties. The doping content influence on the thermal radiationproperties mainly concentrates on the short wave band. Sm2(Zr0.85Ti0.15)2O7has the bestemissivity among Sm2(Zr1xTix)2O7ceramics, while in the Sm2(Zr1xMnx)2O7system,the Sm2(Zr0.9Mn0.1)2O7ceramic shows the best thermal radiation performance.In the IR spectrum, the doping influence on emissivity of Ti4+and Mn4+ionsmainly concentrates on the short wave band of infrared absorption, the absorption peaksnear530cm1and1400cm1response to vibration of Sm-O cubic ligand, while thestrongest absorption peaks near3150cm1and3500cm1is induced by the vibration ofZr-O eight surface ligand. In the absorption spectra, Ti4+and Mn4+ions doped samariumzirconate ceramics can enhance the absorptive capacity in the near infrared, f-f electrontransition effect of the200~500nm band strong absorption peaks due to Sm3+ion, in thenear infrared band, the lattice vibration energy level transition and electronic energytransition of some rare earth ions is mainly contributed to continuous absorption peak of1~2.5m. Those test results well explain the Ti4+and Mn4+ions doped to improve thethermal radiation performance. |
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