1a K, Bi

1b Ti

3c  O

a typical perovskite with substitution of K and Bi

Hi, Bac!

I found a total of three publications dealing with structures with that formula, two older (cubic) and one newer (tetragonal):

"Physical-chemical investigation of the formation of complex ferroelectrics with perovskite structure" [Agranovskaya, A.I.; Izvestiya Akademii Nauk SSSR, Seriya Fizicheskaya (1960), 24, 1275-1281]

"X-ray determination of the symmetry of the ferroelectric compounds K.5 Bi.5 Ti O3 and Na.5 Bi.5Ti O3 and the high-temperature phase transition in K.5 Bi.5 Ti O3 [Ivanova, V.V. et al. Izvestiya Akademii Nauk SSSR, Seriya Fizicheskaya, (1962), 26, 358-360]

"A structural study of the (Na1-x Kx)0.5 Bi0.5 Ti O3 perovskite series as a function of substitution (x) and temperature" [Jones, G.O. et al. Powder Diffraction, (2002), 17(4), 301-319]

Crystal details for the three studies, sorted by year, can be found in the attached file, but I would check out the original references just in case.

Regards,

Daniel

Thanh you very much, Gert Nolze and Daniel Lundberg.

Please note that the tetragonal phase given by Daniel is a subgroup of the cubic phase, caused by a tiny shift of the oxygen arrangement which cause a) a symmetry change, and b) a small deformation of the crystal lattice. The first forces to describe the structure as tetragonal lattice, which might affect the lattice as well but don't have to. Here it does...

Thanks Gert Nolze for nice explanation.