矽酸鹽礦物在地球上是含量最多的礦物，因此最常應用於工業上。合成鹼土族元素之正矽酸鹽類是現今最主要的發光材料之一。鹼土族正矽酸鹽類系列中，Sr2SiO4 與Mg2SiO4在工業上做為螢光材料的寄主體。(Ca,Ba,Sr)2SiO4為同結構之完全固熔體；在Mg2SiO4-Ca2SiO4系列中，發現bredigite (Ca7Mg(SiO4)4)、merwinite (Ca3MgSi2O8)以及monticellite ((Ca,Mg)2SiO4)等結構出現，而Mg2SiO4-Sr2SiO4系列中，只發現merwinite (Sr3MgSi2O8)產物。由於鎂與鈣、鍶之離子半徑相差甚大，本研究探討Mg2SiO4-Sr2SiO4系列是否可形成合成(Mg,Sr)2SiO4完全化學之固熔體。如合成成功，依據不同溫度與化學比例，探討β-K2SO4結構與橄欖石結構兩相之間的變化。或除了β-K2SO4、橄欖石以及merwinite三種結構以外，是否也會出現bredigite與monticellite結構或兩者之外的結構產生。也探討合成Mg2SiO4-Sr2SiO4系列成分，是否會出現化學組成偏移之現象。
樣品分成不同粒徑之原料二氧化矽，燒結900℃、1200℃與1400℃，持溫2至24小時，合成不同之化學成份而生成產物主要結構為HT-Sr2SiO4(K2SO4結構)、LT-Sr2SiO4、merwinite (Sr3MgSi2O8)、akermanite (Sr2MgSi2O7)與鎂橄欖石(Mg2SiO4)等不同結構。依不同溫度及MgO莫耳百分比所產生之以上結構而製作成相圖。以及部分樣品尚有燒結後反應未完全之原料二氧化矽(SiO2)、碳酸鍶(SrCO3)與氧化鎂(MgO)。由EDS化學分析顯示，並無多餘之鎂離子及鍶離子進入上述結構中，出現化學偏移現象。且未發現bredigite與monticellite結構產生。而本研究顯示，改變原料二氧化矽粒徑大小，會造成結構比例改變，以及趨於反應完全產生的merwinite、akermanite與鎂橄欖石結構。

關鍵字: (Mg,Sr)2SiO4、MgO-SrO-SiO2、相圖、結晶結構、化學組成

SUMMARY

In this study, (Mg,Sr)2SiO4 powder samples were synthesized using solid state reaction at different temperatures and durations. XRD analysis indication that the products were shown to be HT-Sr2SiO4, LT-Sr2SiO4, merwinite, olivine, and akermanite in the MgO-SrO-SiO2 series. At the moment, current synthesis results suggest that bredigite- and monticellite-structures would not be formed in (Mg,Sr)2SiO4 compound.
The results of Rietveld refinement indicate that the unit cell volume of the products do not have obvious changes. The experimental results showed that akermanite and merwinite are thermodynamically stable structure in the MgO-SrO-SiO2 ternary system. The phase diagram was made using the XRD results. The use of SEM-EDS chemical analysis showed that the above phases of the partial solid solution were not found.
Experimental results showed that the MgO-SrO-SiO2 series could not form a complete solid solution. The present phases are in various proportions, and their chemical compositions remain unchanged.

Key words: (Mg,Sr)2SiO4, MgO-SrO-SiO2, phase diagram, crystal structure, chemical composition

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