Preparation of the smallest ferroelectric particle of barium titanate and the investigation of its transformation temperature

为了找出最小的四方颗粒的尺寸，研究了以下商业上可用的钛酸钡粉末。它们是酒井化学工业株式会社生产的水热钛酸钡；BT-01和BT-006，其标称尺寸分别为100 nm和6 nm。另一种是KCM公司的粉末，用固相反应法制备了名义尺寸为700 nm的粉末，后者在室温下在1 GPa下重复进行CIP化处理，用粉末X射线衍射、透射电子显微镜和热容测量对其进行了表征。CIPed ONCE粉的Tet-cube转变热是正常粉的1/15。CIP60次后，虽然微晶尺寸减小到47 nm，但仍为四方晶系。此外，通过透射电子显微镜观察发现，BT-01的晶格由折叠的晶界和调制的晶格阵列组成。一些文献报道了BT-01的立方钛酸钡。然而，这项研究表明，所有的…得到的BT-01和BT-006及其加热样品的粉末均为四方相。这一结论是从以下结果得出的，然而，即使是非常仔细的电子衍射检查也没有检测到收到的BT-01粉末上的任何四方体。测量了113个和400个衍射峰的半高宽随温度的变化，以找出它们可逆的变化。这些结果表明，这两个衍射物的半高宽在室温下由于其四方分裂而变宽，而在较高温度时变小。拉曼光谱随温度变化的系统测量支持水热钛酸钡粉末的四方相。我们在样品上检测到立方钛酸钡在150℃处的抑制光谱。也就是说，被抑制的光谱不能用于识别晶体的点群。然而，我们已经监测到在转变温度下抑制光谱强度的急剧可逆变化，从而得出结论：在室温下，样品是四方的钛酸钡。较少

The following commercially available barium titanate powders were investigated with the intentions t find the size of the smallest tetragonal particle. Those were hydrothermal barium titanate made by Sakai Chemical Industry Co., Ltd ; BT-01 and BT-006 with respective nominal sizes of 100 nm and 6 nm, respectively. Another powder of KCM Corp., was made by a solid state reaction with a nominal size of 700 nm.The latter powder was CIPed under 1GPa repeatedly at room temperature to characterize by powder X-ray diffraction, TEM and heat capacity measurements. The tet-cub transformation enthalpy of the CIPed once powder was 1/15 of that of the normal. However, it was tetragonal after CIPed for 60 times although the crystallite size was decreased to 47 nm. Further, tweedy and /or squeezed texture was revealed by TEM to comprise collapsed boundary zones and modulated lattice arrays.Some papers have reported about cubic barium titanate of BT-01. However, this research made it clear that all the … More powders were tetragonal for as received BT-01 ad BT-006, and their heated specimens. This conclusion was derived from following results, however, even very careful electron diffraction examinations failed to detect any tetragonalty on as received powder of BT-01. The half height widths of 113 and 400 diffractions were monitored as functions of temperature to find their reversible changes. These results said that the half height widths of the two diffractions were wide at room temperature because of their tetragonal splittings, and those became smaller at higher temperature that Tc.Systematic measurements of Raman spectrum as functions of temperature supported the tetragonal barium titanate of hydrothermal powders. We had detected on specimens the inhibited spectra for cubic barium titanate at 150℃. That is the inhibited spectra are no use to identify the point group of the crystals. However, we had monitored the sharp reversible changes in intensities of inhibited spectra at transformation temperatures to conclude the specimens were tetragonal barium titanate at a room temperature. Less