以鈦酸鉛為基底之鈣鈦礦粉末X光繞射研究

Abstract

為了利用粉末X光繞射說明多晶結構Pb1-xSrxTiO3 鐵電相變及比對鐵電相變中的LO-TO splitting現象[Appl. Phys. Lett. 81, 3019, (2002)]，我們從摻雜不同的成分Sr，經由Rietveld refinement 分析發現在Pb1-xSrxTiO3 系統中Pb原子位移程度大於Ti，並經計算Pb-O及Ti-O鍵長的變化有明顯不同。 基於X光繞射理論而言，繞射峰強度表示出原子位置和原子散射因子，並且原子散射因子卻反映出原子內的電子雲對X光的散射能力，因此參雜不同成分Sr ，Pb和Ti原子位移變化程度不同的原因是由於Pb2+ 與Sr2+的電子狀態不同而導致，我們提出此原因是由於Pb-O的共價鍵影響大於Sr-O的離子鍵而導致庫倫力的影響被減弱，影響Ti-O共價鍵的變化。

For using powder X-ray diffraction explains ferroelectric phase transition in polycrystalline Pb1-xSrxTiO3 and contrasts to the decreasing giant LO-TO splitting [Appl. Phys. Lett. 81, 3019, (2002)], a direct observation of the variation of displacement in Pb is larger than Ti, used Rietveld refinement, and Pb-O bonding length calculated differs greatly from Ti-O. In view of XRD theories, the intensity of Bragg peaks represents atomic position and atomic scattering factor. Simultaneously, the electronic densities in atom are reflected by atomic scattering factor. Therefore, the extent of displacement in Pb differing from Ti doped Sr atom can be proposed that the Pb-O interaction is more hybridized than Sr-O, reduces the effect of long-range Coulomb interaction. Furthermore, Pb-O interaction may play important role than Ti-O in Pb1-xSrxTiO3 system.