| abstract |
This crystalline material is represented by M 1 n 2a (M 2 n b L c )M 3 n d O y N x , where: M 1 is at least one type of element selected from the alkali metals; M 2 is at least one type of element selected from Ca, Sr and Ba; M 3 is at least one type of element selected from Si and Ge; L is at least one type of element selected from the rare earth elements, Bi and Mn; a is 0.9 to 1.5; b is 0.8 to 1.2; c is 0.005 to 0.2; d is 0.8 to 1.2; x is 0.001 to 1.0; and y is 3.0 to 4.0. |