The effects of titanium and molybdenum substitution on the electric and photoelectric properties of potassium niobate

• Main Authors: Yun-SyuanLin, 林昀萱
• Other Authors: Xiao-Ding Qi
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/81884629024026058860

碩士 === 國立成功大學 === 材料科學及工程學系 === 102 === The aim of this study was to search for ferroelectric photovoltaic materials. 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 such a purpose, KNbO3 was doped with different ions in this study. Polycrystalline samples of KNbO3:M (M=Ti and Mo) were prepared by the solid-state reaction method. X-ray diffraction showed that a pure phase of Ti or Mo doped KNbO3 could be obtained after sintering at 1000 C for 8 and 10 hours, respectively, and the doping limit was below 10 at.%, above which secondary phases occurred. The Currie temperature of KNbO3 was reduced by 20~30 C by the doping. The resistivity of KNbO3:5%Ti was measured to be 7.04108 ohm-cm, an order of magnitude smaller than the un-doped KNbO3 (7.82109 ohm-cm), whereas the Mo doped samples showed a slightly higher resistivity than the un-doped KNbO3. After electrical poling in a high field, the current-voltage curves of the samples were measured with and without light irradiation. For the un-doped KNbO3 there was virtually no change in the output current before and after the illumination, indicating a lack of the carriers that could be activated by the light. However, both Ti and Mo doped KNbO3 showed an order of magnitude increase in the output current after the illumination.