COMBINED X-RAY AND NEUTRON POWDER DIFFRACTION STUDY OF MAGNESIUM-DOPED LITHIUM-NIOBATE

The nature of cation doping in the important optical material lithium niobate has been studied using a combination of X-ray and neutron powd er diffraction methods. Samples of nominal composition Li1-xMgxNbO3 (x = 0.1, 0.2, 0.3) were studied. Magnesium was found to substitute excl usively at the Li site, with concommitant Li vacancies, and with no de viation from stoichiometry at the Nb position, i.e. [Li1-xMgx/2][Nb]O- 3. This is the first detailed structural study of doped lithium niobat e by diffraction methods and supports previous models obtained by loca l structural techniques and computational methods.