氧化鎂與氧化釩混合粉末 之雷射燒結機制研究

Abstract

本文研究利用拉曼光譜觀察雷射光照射MgO+ V2O5不同比例混合粉末樣品，此粉末樣品預先經攝氏400度加熱三小時鍛燒處理，欲探討樣品經雷射照射後產生MgV2O6與Mg2V2O7結構的相變過程與相變機制。由高斯型態雷射光照射樣品所致的相變結果與能量分佈關係連結，可以得到樣品相變程度大致與高斯能量分佈成正相關。再經由X光吸收光譜與螢光激發光譜輔助確認混合粉末樣品的缺陷存在，與缺陷所導致的發光位置後，以514.5nm與532nm雷射為光源，以不同能量照射於MgO+ V2O5不同比例混合粉末，再由雷射照射後新結構生成的結果推論，導致樣品相變的能量來自於光子與電子之間的交互作用。如此一來，結合X光吸收光譜與螢光光譜，我們可以建立一個能量轉換的可能模型。 另外藉由雷射連續照射樣品同時量測所得的高溫態拉曼光譜，可以得到樣品在相變過程的結構變化訊息。X光吸收光譜也提供了樣品結構對稱性高低的資訊，搭配群論分析結果，可以解釋高溫態光譜中聲子的變化，進而推測樣品新結構形成的可能方式。

In this research, our samples were calcined ( 400 oC, 3 hours) mixtures of MgO and V2O5 powders in different proportions. We irradiated our sample powders with laser beams, and samples that heated by laser were examined by Raman spectroscopy to determine the crystalline structure. Controlling the laser heating time and power, and heated powder samples formed similar crystal as found in conventional hearting. This study can resolve the process and mechanism of MgV2O6 and Mg2V2O7 crystalline formation. When we treated the samples with Gaussian beams, we found that there is a positive correlation between the degree of phase transition and Gaussian energy distribution. Using 514.5nm and 532nm laser as irradiating light and controlled the laser power, the heating result we analyze from Raman spectra told us the energy cause crystalline were originated from photons. Plus X-ray absorption spectrum(XAS) and Photoluminescence(PL) result, we could build a very possible model of energy transfer for laser heating. Furthermore, we could get the continuous information of phase transition by heating our samples uninterruptly and recording Raman spectra in the same time. There spectra showed us the high temperature messages of our sample, and the change of phonon vibration during the heating process. Because of the changes of phonon vibration reflect the structure change, we could ratiocination the way of our sample crystalline with the help of group theory analysis and X-ray absorption spectrum.