Control of Texture in Electroceramics by Slip-Casting in a High Magnetic Field
Control of Texture in Electroceramics by Slip-Casting in a High Magnetic Field
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高磁场中注浆成型对电陶瓷织构的控制
DOI：
10.4028/www.scientific.net/kem.248.191
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发表时间：
2003
期刊：
影响因子：
--
通讯作者：
Y. Sakka
中科院分区：
文献类型：
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作者：
Tohru S. Suzuki;Y. Sakka
控制陶瓷的织构是提高陶瓷性能的有效途径之一。ZnO和TiO 2的各向异性磁化率很小，因此，利用磁场很难形成织构化的微结构。但在本文中，我们证明，织构的ZnO和TiO 2可以通过在高磁场中的胶体加工，然后加热制备。在烧结之前获得具有轻微结晶取向度的绿色固体。织构的程度随温度的升高而增加，并且晶体织构的发展伴随着试样的致密化和晶粒长大。氧化锌和二氧化钛是重要的电子陶瓷，用于各种应用。具有主要c轴取向的氧化锌对于声学和压电器件是有用的，这是由于这些效应的大耦合系数。控制氧化锌晶体取向是有效改善这些性能的途径之一。具有非对称晶胞的陶瓷表现出各向异性织构，但在ZnO、TiO 2等抗磁性和顺磁性陶瓷中，各向异性织构很小，因此通常难以利用磁场控制这些陶瓷的织构。近年来，超导磁体的发展扩大了高磁场的潜在应用。已经报道了与高磁场相关的有趣现象[1，2]，并且磁场已经用于在许多种类的材料中产生织构化的微结构[3 - 6]。具有各向异性磁化率的晶体在置于磁场中时将旋转到使系统能量最小化的角度。在旋转时磁能的减少是Δ E = −（Δ x VB）/2μ0，其中Δ x = χa，B−χc是磁化率的各向异性，V是每个粒子的体积，μ0是真空中的磁导率，B是所施加的磁场。这是磁排列的驱动力。粉末在悬浮液中的分散对于磁场的有效利用是必要的，因为悬浮液中团聚颗粒之间的强相互作用防止每个颗粒在磁场的施加下旋转。在本研究中使用胶体加工，因为该加工在形成致密化细颗粒方面非常有效，从而通过使用排斥表面力避免了非均匀团聚体[7]。
The control of texture in ceramics is one of the ways for effec tively improving their properties. Anisotropic susceptibility is very small in ZnO and TiO 2; therefore, it had been very difficult to developing the textured microstructure using a magnetic field. But we demonstrate in this paper that the textured ZnO and TiO 2 can be prepared by a colloidal processing in a high magnetic field followed by heating. A green solid with a slight degree of crysta llographic orientation was obtained before sintering. The degree of texture increased with increasing temperature, and crystallographic texture development accompanies the densification and grain growth in the specimens. INTRODUCTION Zinc oxide and titania are important electronic ceramics for use in diverse applications. Zinc oxide with a predominantly c-axis orientation is useful for acoustic and pi ezoelectric devices as a result of the large coupling coefficients for these effects. The controlled d velopment of the crystal orientation in zinc oxide is one of the ways for effectively improving these propertie s. Ceramics with asymmetric unit cells show anisotropic susceptibi lity, but it is very small in diamagnetic and paramagnetic ceramics such as ZnO and TiO 2; therefore, it is generally difficult to utilize a magnetic field for controlling the texture in these c eramics. Recently, the development of superconducting magnets has been extending the potential applications of hi gh magnetic fields. Interesting phenomena associated with high magnetic fields have been reported [1,2] and magnetic fields have been used to produce a textured microstructure in many kinds of materials [3 -6]. A crystal with an anisotropic magnetic susceptibility will rot ate to an angle minimizing the system energy when placed in a magnetic field. The reduction of the magneti c energy on the rotation is ∆E = −(∆χVB)/2μ0, where ∆χ = χa,b−χc is the anisotropy of the magnetic susceptibility, V is the volume of each particle, μ0 is the permeability in a vacuum and B is the applied magnetic field. This is the driving force for magnetic alignment. The dispersion of powder in a suspension is necessary for effective ut ilization of the magnetic field, because a strong interaction between the agglomerated particles in a uspension prevents each particle from rotating under the application of a magnetic field. C olloidal processing was used in this study because the processing is very effective in developing cons olidated fine particles, thereby avoiding heterogeneous agglomerates, by using repulsive surface forces [7].