The effects of calcium and other element substitution on the electric and photoelectric properties of bismuth ferrite
碩士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 101 === The aim of this study was to search for ferroelectric photovoltaic materials. In contrast to the semiconductor p-n junction, where the photovoltaic voltage is limited to around 0.6 V, the spontaneous polarization in ferroelectric materials can produce a...
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ndltd-TW-101NCKU51590272016-03-18T04:42:17Z http://ndltd.ncl.edu.tw/handle/41204950239370020978 The effects of calcium and other element substitution on the electric and photoelectric properties of bismuth ferrite 金屬鈣和其他元素摻雜對鐵酸鉍導電及光電性質之影響 Wang-JenLi 李婉甄 碩士 國立成功大學 材料科學及工程學系碩博士班 101 The aim of this study was to search for ferroelectric photovoltaic materials. In contrast to the semiconductor p-n junction, where the photovoltaic voltage is limited to around 0.6 V, the spontaneous polarization in ferroelectric materials can produce a much higher output voltage. Indeed, in a recent work, a large photovoltaic output of over 20 V has been demonstrated with the BiFeO3 single crystals. However, because ferroelectric materials usually have a very high DC resistivity over 108 ohm-cm, there is a need to increase the mobile carrier concentration in these materials. For this purpose, BiFeO3 (BFO) was doped with various ions in the present study. Polycrystalline pellets of BFO:M (M=Ca, Pb, Sr and Ni) were prepared by the sol-gel method. After poling, the photoelectric effects of the samples were studied. X-ray diffraction showed that after sintering at 500~600oC for 12 hours, undoped BFO and the samples doped with Ca, Pb, Sr and Ni had a pure phase with the well-known rhombohedral structure. If the sintering temperature was raised to 700oC, a second phase of the composition Bi25FeO40 appeared. The resistivities of the BFO samples doped with Ca, Pb, Sr, and Ni doped were measured to be 106~107 ohm-cm, which were1~2 orders lower than that of the undoped BFO. The samples were poled under a high electrical field at 600oC. The degree of the achieved poling was checked by the measured d33 values. I-V curves and photovoltaic effects of the samples with a large d33 were then investigated. The experiment results showed that under suitable preparation conditions (e.g. sintering temperature and time, degree of achieved poling, etc.), an open-circuit voltage was usually observed in the samples. After the samples were illuminated by the simulated-sunlight, large current increases were observed in the I-V curves. The undoped BFO showed a largest negative open-circuit voltage of -1.25 V, whereas the open-circuit voltages for Ca and Ni doped BFO were -0.75 and -0.2 (V), respectively. On the other hand, The Ca and Ni doped samples showed the largest photocurrents, which were increased from 10-9 A at dark to 10-8 A after the illumination. The undoped BFO showed a trivial photocurrent after illumination, indicating a lack of mobile charge carrier which could be excited by the light. Xiaoding Qi 齊孝定 2013 學位論文 ; thesis 101 zh-TW |
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碩士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 101 === The aim of this study was to search for ferroelectric photovoltaic materials. In contrast to the semiconductor p-n junction, where the photovoltaic voltage is limited to around 0.6 V, the spontaneous polarization in ferroelectric materials can produce a much higher output voltage. Indeed, in a recent work, a large photovoltaic output of over 20 V has been demonstrated with the BiFeO3 single crystals. However, because ferroelectric materials usually have a very high DC resistivity over 108 ohm-cm, there is a need to increase the mobile carrier concentration in these materials. For this purpose, BiFeO3 (BFO) was doped with various ions in the present study. Polycrystalline pellets of BFO:M (M=Ca, Pb, Sr and Ni) were prepared by the sol-gel method. After poling, the photoelectric effects of the samples were studied.
X-ray diffraction showed that after sintering at 500~600oC for 12 hours, undoped BFO and the samples doped with Ca, Pb, Sr and Ni had a pure phase with the well-known rhombohedral structure. If the sintering temperature was raised to 700oC, a second phase of the composition Bi25FeO40 appeared. The resistivities of the BFO samples doped with Ca, Pb, Sr, and Ni doped were measured to be 106~107 ohm-cm, which were1~2 orders lower than that of the undoped BFO. The samples were poled under a high electrical field at 600oC. The degree of the achieved poling was checked by the measured d33 values. I-V curves and photovoltaic effects of the samples with a large d33 were then investigated.
The experiment results showed that under suitable preparation conditions (e.g. sintering temperature and time, degree of achieved poling, etc.), an open-circuit voltage was usually observed in the samples. After the samples were illuminated by the simulated-sunlight, large current increases were observed in the I-V curves. The undoped BFO showed a largest negative open-circuit voltage of -1.25 V, whereas the open-circuit voltages for Ca and Ni doped BFO were -0.75 and -0.2 (V), respectively. On the other hand, The Ca and Ni doped samples showed the largest photocurrents, which were increased from 10-9 A at dark to 10-8 A after the illumination. The undoped BFO showed a trivial photocurrent after illumination, indicating a lack of mobile charge carrier which could be excited by the light.
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author2 |
Xiaoding Qi |
author_facet |
Xiaoding Qi Wang-JenLi 李婉甄 |
author |
Wang-JenLi 李婉甄 |
spellingShingle |
Wang-JenLi 李婉甄 The effects of calcium and other element substitution on the electric and photoelectric properties of bismuth ferrite |
author_sort |
Wang-JenLi |
title |
The effects of calcium and other element substitution on the electric and photoelectric properties of bismuth ferrite |
title_short |
The effects of calcium and other element substitution on the electric and photoelectric properties of bismuth ferrite |
title_full |
The effects of calcium and other element substitution on the electric and photoelectric properties of bismuth ferrite |
title_fullStr |
The effects of calcium and other element substitution on the electric and photoelectric properties of bismuth ferrite |
title_full_unstemmed |
The effects of calcium and other element substitution on the electric and photoelectric properties of bismuth ferrite |
title_sort |
effects of calcium and other element substitution on the electric and photoelectric properties of bismuth ferrite |
publishDate |
2013 |
url |
http://ndltd.ncl.edu.tw/handle/41204950239370020978 |
work_keys_str_mv |
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