Neutron Total Scattering Studies of Group II Titanates (ATiO3, A2+ = Mg, Ca, Sr, Ba)
Charles M. Culbertson, Alexander T. Flak, M. M. Yatskin, Paul Ha‐Yeon Cheong, David P. Cann, Michelle Dolgos
Abstract
Abstract Neutron total scattering measurements were conducted on MgTiO 3 , CaTiO 3 , SrTiO 3 , and BaTiO 3 to simultaneously investigate the local and average structure of these materials. The local structures of MgTiO 3 , CaTiO 3 , and SrTiO 3 were well modelled using the refined average structural models: trigonal R $$\bar{3}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover><mml:mn>3</mml:mn><mml:mo>¯</mml:mo></mml:mover></mml:mrow></mml:math> , orthorhombic Pbnm , and cubic Pm $$\bar{3}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover><mml:mn>3</mml:mn><mml:mo>¯</mml:mo></mml:mover></mml:mrow></mml:math> m respectively. However the local structure for BaTiO 3 , at both temperatures where the average structure is orthorhombic Amm 2 and tetragonal P 4 mm , was best described by the rhombohedral R 3 m model. Only the R 3 m model was able to account for the observed displacement of titanium in the [111] direction. Furthermore, box-car type refinements were conducted. These refinements show that the coherence length of the rhombohedral distortion is around 10 Å, at larger r -ranges the local distortions become misaligned and average out to Amm 2 and P 4 mm .