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Ca0.64WO4:Eu0.24 also crystalizes in the phase of CaWO4 with about 12 mol% of Schottky defects on Ca2+-sites in the crystal lattice of CaWO4. The question whether such a phase is well stable at high temperatures remains to be studied, so the impacts of over-sintering on the structure of Ca0.64WO4:Eu0.24 ceramics are examined. The probable origins resulting in the phase transition at high temperatures are discussed, and the influences of such a phase transition on the luminescence properties are also studied. Observations reveal that some oxygen ions bonded to Schottky defects may be released when the sintering temperature is over 1100 ℃. This leads to the shortage of oxygen element for the bulk Ca0.64WO4:Eu0.24 ceramics, and a phase transition in CaWO4 may have occurred. A monoclinic phase of the formula Eu2 WO6 is generated. It is found that the distance between crystal planes in CaWO4 becomes larger after the phase transition. This may be one of the primary reasons accounting for the sharp decrease of luminescent intensities of Ca0.64WO4:Eu0.24 ceramics.
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Keywords:
- phase transition /
- calcium tungstate /
- europium /
- luminescence
[1] Errandonea D, Manjon F J, Somayazulu M, Hausermann D 2004 J. Solid State Chem. 177 1087
[2] Senyshyn A, Kraus H., Mikhailik V B, Yakovyna V 2004 Phys. Rev. B 70 214306
[3] Pang H F, Li Z J, Xiang X, Zhang C L, Fu Y Q, Zu X T 2011 Chin. Phys. B 20 116104
[4] Basiev T T, Sobol A A, Voronko Y K, Zverev P G 2000 Opt. Mater. 15 205
[5] Shi S K, Gao J, Zhou J 2008 Opt. Mater. 30 1616
[6] Gao Y, L Q, Wang Y, Liu Z B 2012 Acta Phys. Sin. 61 077802 (in Chinese) [高杨, 吕强, 汪洋, 刘占波 2012 61 077802]
[7] Kuang J Z 2011 Journal of Functional Materials 42 1390 (in Chinese) [匡敬忠 2011 功能材料 42 1390]
[8] Hu Q, Lin X, Yang G L, Huang W D, Li J F 2012 Acta Metall. Sin. 48 1467 (in Chinese) [胡桥, 林鑫, 杨高林, 黄卫东, 李金富 2012 金属学报 48 1467]
[9] Wang B G, Shi E W, Zhong W Z, Yin Z W 1998 J. Inorg. Mater. 12 648 (in Chinese) [王步国, 施尔畏, 仲维卓, 殷之文 1998 无机材料学报 12 648]
[10] Achary S N, Patwe S J, Mathews M D, Tyagi A K 2006 J. Phys. Chem. Solids 67 774
[11] Huang Y L, Wang X G, Xiao G X 2007 Journal of Synthetic Crystals 36 1324 (in Chinese) [黄彦林, 王锡钢, 肖国先 2007 人工晶体学报 36 1324]
[12] Shi S K, Liu X R, Gao J, Zhou J 2008 Spectrochim. Acta, Part A 69 396
[13] Wu H E, Yang X Y, Yu X B, Liu J, Yang H, L H B, Yin K Z 2009 J. Alloys Compd. 480 867
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[1] Errandonea D, Manjon F J, Somayazulu M, Hausermann D 2004 J. Solid State Chem. 177 1087
[2] Senyshyn A, Kraus H., Mikhailik V B, Yakovyna V 2004 Phys. Rev. B 70 214306
[3] Pang H F, Li Z J, Xiang X, Zhang C L, Fu Y Q, Zu X T 2011 Chin. Phys. B 20 116104
[4] Basiev T T, Sobol A A, Voronko Y K, Zverev P G 2000 Opt. Mater. 15 205
[5] Shi S K, Gao J, Zhou J 2008 Opt. Mater. 30 1616
[6] Gao Y, L Q, Wang Y, Liu Z B 2012 Acta Phys. Sin. 61 077802 (in Chinese) [高杨, 吕强, 汪洋, 刘占波 2012 61 077802]
[7] Kuang J Z 2011 Journal of Functional Materials 42 1390 (in Chinese) [匡敬忠 2011 功能材料 42 1390]
[8] Hu Q, Lin X, Yang G L, Huang W D, Li J F 2012 Acta Metall. Sin. 48 1467 (in Chinese) [胡桥, 林鑫, 杨高林, 黄卫东, 李金富 2012 金属学报 48 1467]
[9] Wang B G, Shi E W, Zhong W Z, Yin Z W 1998 J. Inorg. Mater. 12 648 (in Chinese) [王步国, 施尔畏, 仲维卓, 殷之文 1998 无机材料学报 12 648]
[10] Achary S N, Patwe S J, Mathews M D, Tyagi A K 2006 J. Phys. Chem. Solids 67 774
[11] Huang Y L, Wang X G, Xiao G X 2007 Journal of Synthetic Crystals 36 1324 (in Chinese) [黄彦林, 王锡钢, 肖国先 2007 人工晶体学报 36 1324]
[12] Shi S K, Liu X R, Gao J, Zhou J 2008 Spectrochim. Acta, Part A 69 396
[13] Wu H E, Yang X Y, Yu X B, Liu J, Yang H, L H B, Yin K Z 2009 J. Alloys Compd. 480 867
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