Preferred Orientations of Crystalline Phases Formed by Heat Treatments of BaO-B_2O_3-Fe_2O_3 Amorphous Oxides

研究了一种控制陶瓷材料晶体织构的方法。以35mol%BaO-47mol%B_2O_3-18mol%Fe_2O_3和37mol%BaO-40mol%B_2O_3-23mol%Fe_2O_3为氧化物，分别采用单辊淬火和双永久模间快速凝固的方法，制备出薄带状和1 mm厚钮扣状试样。用x射线对样品进行了分析，用差热分析法测定了结晶温度（Tx1和Tx2）。带状试样在均匀加热的炉中结晶，纽扣状试样夹在冷热金属块之间，使结晶在温度梯度下进行。当在Tx1和Tx2温度之间加热时，观察到一个未知的亚稳相。在Tx2温度以上的试样中发现BaOB_2O_3相。利用针孔相机的x射线衍射方法在带状材料中发现了近（100）[010]优选取向。纽扣样样品的x射线极位图显示，光学显微镜观察到柱状晶体的生长方向接近[101]，与温度梯度平行。这一初步研究表明，非晶材料的控制结晶是制备多晶各向异性陶瓷的一种很有前途的方法。

A method is studied to control crystallographic textures of ceramic materials. Thin ribbon-like and 1 mm thick button-like specimens were made of molten 35mol%BaO-47mol%B_2O_3-18mol%Fe_2O_3 and 37mol%BaO-40mol%B_2O_3-23mol%Fe_2O_3 oxides by rapid solidification using single roll quenching and pressing between two permanent moulds, respectively. The specimens were examined by X-ray analysis and temperatures of crystallization (Tx1 and Tx2) were determined by DTA method. The ribbon-like specimens were crystallized in a uniformly heated furnace, while the button-like ones were sandwiched between hot and cold metal blocks so that the crystallization proceeded under temperature gradient. An unidentified metastable phase is observed, when heated between Tx1 and Tx2 temperatures. The BaOB_2O_3 phase is identified in specimens heated above Tx2 temperature. A near (100)[010] preferred orientation is found in the ribbon-like imens by an X-ray diffraction method using pinhole camera. X-ray pole figures of the button-like specimen show a near [101] preferred orientation of columnar crystals observed by optical microscope to have grown parallel to the temperature gradinet. This preliminary srudy has demonstrated that the controlled crystallization of amorphous materials is promising as a method to produce polycrystalline but anisotropic ceramics.