Structural and thermal evolution studies of LaSbO4 ceramics prepared by solid-state reaction method.

Abstract

This work investigates the thermal evolution of LaSbO4 ceramics produced by solid-state method in the temperature range 700e1500 _C, for 6 h. Besides the expected phase transitions, a thermal decomposition at high temperatures to La3SbO7 was observed and discussed. The results showed that the phase LaSbO4 can be obtained only below 1450 _C, while temperatures lower than 1100 _C are not able to produce crystalline structures. The samples were submitted to X-ray diffraction and Raman scattering measurements aiming to determine their crystal structures. LaSbO4 materials exhibited monoclinic structures, space group P21/m ¼ C2 2h(#11), with Z ¼ 4. It was verified that all the 36 Raman-active modes predicted by group-theory calculations were observed. Also, the symmetries could be discerned by using polarized Raman scattering, which allow us to assign the gerade modes. Luminescence properties of LaSbO4 were investigated and the results showed that this compound exhibits sensitivity of the host lattice to UV excitation. PL spectra excited at 360 nm have a blue emission band maximum at 428 nm, corresponding to the self-activated luminescence center of LaSbO4.