As apparent from the following Table 3, in Comparative Examples A-1a and A-1b, the obtained results of the intensity ratio IL/IH of the diffraction peaks were different from each other, though the target compositions are the same. In Comparative Example A-1a, the sintering was performed at one time at 1000° C. for a long time without considering the vaporization amount of Li. On the other hand, in Comparative Example A-1b, the synthesis was performed in the same manner as in Example A-1 of the present application. It can be considered therefore that if the sintering condition or the feed amount of the lithium starting materials is different, the crystallite growing condition is also different.
On the other hand, the results of the powder X-ray diffraction were analyzed according to a Rietveld method. As a result, it was found that the products obtained in Examples A-1 to A-14 were orthorhombic type compounds having the space group Fmmm symmetry shown in