【作者】 王学军；

【导师】 卢铁城；

【作者基本信息】 四川大学 ， 凝聚态物理， 2007， 硕士

【摘要】 自Ikesue等人于1995年首次制备出透明陶瓷Nd：YAG激光材料以来，并实现激光输出后，透明激光材料引起了人们的极大兴趣，现已制备出很多种激光材料，但到目前为止，可见波段透明陶瓷激光材料的还未引起足够的重视。本文研究了一种可用于可见波段的激光材料—掺锰铝酸镁（Mn：MgAl₂O₄）透明陶瓷。据作者目前所掌握的资料，关于掺锰铝酸镁粉体和透明陶瓷的研究还鲜有报道；制备了具备不能掺杂浓度的掺锰铝酸镁粉体和透明陶瓷，通过对样品的表征及光学性质分析，初步确定了最佳掺杂浓度，并讨论了其发光机制。实验中，以分析纯NH₄Al_SO42·12H₂O和MgSO₄·7H₂O，以及适量掺杂剂MnSO₄·H₂O为原料，根据产物的化学式Mn_xMg_1-xAl₂O₄称取原料，利用高温焙烧法制备了具有一系列掺杂浓度的掺锰铝酸镁粉体。然后用真空烧结（烧结温度为1750℃，保温时间为2小时）制备出了相应的掺锰铝酸镁陶瓷并对部分样品进行了热等静压后处理（1650℃，200MPa，2h）。通过X射线衍射（XRD）、扫描电境（SEM）等测试分析手段，测试分析了制备的陶瓷的物相组成，陶瓷的断口形貌等。同时利用紫外—可见分光光度计及荧光分光光度计等测试分析手段对陶瓷在紫外—可见波段的透过谱和光荧光谱进行了测试分析。制备出的掺锰铝酸镁陶瓷呈两种颜色：绿色和褐色。当掺杂浓度低于10％时，样品呈绿色，且其颜色随着掺杂浓度的增加而加深。当掺杂浓度提高至14％时，其颜色由绿色转变成褐色，其颜色亦随着掺杂浓度的增加而加深。XRD分析表明，呈绿色的样品仅存在尖晶石相，无杂相；而呈褐色的样品除有尖晶石相以外，还存在一新相Mg_0.9Mn_0.1O。通过对具有不同掺杂浓度的样品的微观形貌和透过性质的测试分析得到以下结果：由于存在很多晶内、晶间气孔、气泡等，真空烧结制备的掺锰铝酸镁透明陶瓷样品在紫外-可见波段透过率较低；通过热等静压处理后，其透明度仍未能得到很大的改善；样品在400-500nm范围内有两个相对强的吸收峰，且当掺杂浓度大于5at．％时，在270nm、357nm和382nm处也有微弱的吸收峰，这些吸收峰强度比较弱的原因是与这些吸收峰对应的跃迁都是自旋禁阻的，跃迁几率比较小。光荧光谱测试结果表明，在520nm附近观察到样品的一个强的发射峰，对应于跃迁⁴T₁（4^G）→⁶A₁，掺杂浓度为10at.％的样品的该发射峰最强，当掺杂浓度达到14at．％时，该发射峰强度急剧下降；此外，未发现掺杂浓度高于14at．％的样品在可见波段存在新的可用的荧光峰；故可初步判定10at．％为最佳掺杂浓度。此外，还给出了相应的激发谱对应的跃迁机制。更多还原

【Abstract】 Postgraduate Wang Xuejun Supervisor Professor Lu TiechengSince A. Ikesue et al. first developed Nd:YAG transparent ceramics andaccomplished laser output in 1995, transparent ceramic laser materials have arousedgreat interests among the world. Many ceramic laser materials have been preparedsince then. But up to now, visible-band ceramic laser material has not been paidmuch attention. In this paper, Mn:MgAl₂O₄ transparent ceramics which possesspotential application in visible-band laser material were studied. As far as I know,Mn:MgAl₂O₄ powders and transparent ceramics has been rarely reported.Mn:MgAl₂O₄ powders and transparent ceramics with different dopingconcentrations were prepared. The optimal doping concentration was approximatelydetermined through XRD and Photoluminescence analyses. In addition, themechanism for fluorescence of Mn:MgAl₂O₄ transparent ceramics was discussed.In experiment, Mn:MgAl₂O₄ powders with a series of doping concentrationswere synthesized by a high-temperature calcination method using analytically pureNH₄Al（SO₄）2·12H₂O, MgSO₄·7H₂O and a certain amount of MnSO₄·H₂O used asdopant as raw materials. Then, Mn: MgAl₂O₄ transparent ceramics were preparedthrough vacuum sintering（1750℃, 2h） using previously obtained powders and someof the as-prepared samples were treated by post hot isostatic pressing（HIP 1650℃,200MPa, 2h）. By means of X-Ray diffraction（XRD）, Scanning ElectricalMicroscopy（SEM） analysis, compositional phases of ceramics, fracture facemorphology were studied. At the same time, the transmittance in ultraviolet and visible-band and photoluminescence were investigated using UV-VIS spectrometerand fluorescence spectrometer.Prepared ceramic samples exhibit two kinds of color, green and brown. Sampleshaving doping concentrations not larger than 10% exhibit green color. The colorbecomes deeper with increasing doping concentration. When the dopingconcentration increases to 14%, its color changes into brown from green and alsobecomes deeper when doping concentration further increases. XRD analysisindicated that no impurity phase was detected for green samples. Whereas, a newphase Mg_0.9Mn_0.1O was detected for brown samples.It can be obtained though the observation of fracture face morphology and themeasurement of transmittance of samples with different doping concentrations thatthe transmittance in ultraviolet and visible-band is rather low due to manyinner-grain and intergranular pores as well as bubbles; their transparency was nothighly improved by post-HIP treatment; There are two relatively strong absorptionpeaks in the range of 400-500nm and when the doping concentration is higher than5at.%, weak absorption peaks at 270nm, 357nm and 382nm appear too. Theseabsorption peaks are very weak for the reason that their corresponding transitionsare spin-forbidden, resulting in small transition probabilities.The analyses of the tests of photoluminescence showed that a strong emissionpeak around 520nm, corresponding to the transition ⁴T₁（⁴G）→⁶A₁, was observed.The emission intensity showed the maximum for 10at.% Mn-doped samples. Itsintensity dropped dramatically when the doping concentration reached 14at.%. Nonew useful emission peaks in visible-band were observed for samples with dopingconcentrations higher than 14%. So, the optimal doping concentration wasapproximately determined as 10at.%. In addition, the mechanism for correspondingexcitation spectrum was given.更多还原