Epitaxial growth of ∈-Fe2O3 on mullite found through studies on a traditional Japanese stoneware

In the course of our study on a Japanese traditional stoneware called Bizen, we have found that is an element of-Fe2O3, which has been classically known but recently limelighted for its magnetic potentiality, crystallizes epitaxially on needlelike crystals of mullite, 3(Al,Fe)(2)O-3 center dot 2SiO(2). This interesting reaction occurred when a pellet of Bizen clay powder was covered with rice straw and then heated to 1250 degrees C in a stream of nitrogen containing 1-2 vol % of oxygen. It is known that mullite forms from the clay on heating and that the rice straw provides potassium to induce partial melting in the pellet surface to a depth of similar to 50 mu m. The is an element of-Fe2O3-on-mullite particles formed in this molten region, changing their morphology with the oxygen partial pressure. Square-columnar single-crystalline particles with prismatic ends grew to similar to 0.1 x 0.1 x 0.5 mu m(3) at N-2/O-2 = 99/1, while dendritic finlike crystals of similar to 0.3 x 0.1 x 0.8 mu m(3), which was then the biggest size ever reported, grew at N-2/O-2 = 98/2. The relative is an element of-Fe2O3-to-mullite orientation also changed with the oxygen partial pressure. This discovery suggests morphological controllability of this metastable but magnetically interesting iron oxide as a function of the oxygen partial pressure.