STUDY ON K2SeO4 AT DIFFERENT TEMPERATURES

The crystal structure determination of K2SeO4 and the X-ray powder diffraction analysis have been canied out at different temperatures. The X-ray powder diffraction corroborate the two transitions from paraelectric to incommensurate and from this to ferroelectric phase. This study shows, also, an inhomogeneous behavior of K2SeO4 when the temperature decreases. The crystal structure determination shows the oxygen atoms of the selenate ion do not show the same effective charge. The study at different temperature shown a rotation of SeO4-2 ion around the c-axis and the lengthening of Se-O bond when the temperature is lower. From the structural data, the librational study and the distortion theory we deduce that K(1) is the main ion that produces the different transitions. The incommensurate phase is essentially produced by the freedom of K(1) ion to have a displacement along the a-axis together with a libration of selenate ion about the b-axis. A rotation of the selenate ion around the b-axis together with the displacement of cations produces the ferroelectric phase.