Characterization of the thermal expansion in the rare earth di-titanates is important for their use in high-temperature structural and dielectric applications. Powder samples of the rare earth di-titanates R₂Ti₂O₇ (or R₂O₃·2TiO₂), where R = La, Pr, Nd, Sm, Gd, Dy, Er, Yb, Y, which crystallize in either the monoclinic or cubic phases, were synthesized for the first time by the solution-based steric entrapment method. The three-dimensional thermal expansions of these polycrystalline powder samples were measured by in situ synchrotron powder diffraction from 25°C to 1600°C in air, nearly 600°C higher than other in situ thermal expansion studies. The high temperatures in synchrotron experiments were achieved with a quadrupole lamp furnace. Neutron powder diffraction measured the monoclinic phases from 25°C to 1150°C. The La₂Ti₂O₇ member of the rare earth di-titanates undergoes a monoclinic to orthorhombic displacive transition on heating, as shown by synchrotron diffraction in air at 885°C (864°C–904°C) and neutron diffraction at 874°C (841°C–894°C).

中文翻译：

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稀土双钛酸盐 (R2Ti2O7) 体系中的热膨胀和相变

稀土二钛酸盐的热膨胀特性对于它们在高温结构和介电应用中的使用很重要。稀土双钛酸盐R ₂ Ti ₂ O ₇（或R ₂ O ₃ ·2TiO ₂）的粉末样品，其中R = La、Pr、Nd、Sm、Gd、Dy、Er、Yb、Y，在无论是单斜相还是立方相，都是首次通过基于溶液的空间截留法合成。这些多晶粉末样品的三维热膨胀是通过原位测量的在空气中从 25°C 到 1600°C 的同步加速器粉末衍射，比其他原位热膨胀研究高近 600°C 。同步加速器实验中的高温是用四极灯炉实现的。中子粉末衍射测量了 25°C 至 1150°C 的单斜晶相。稀土双钛酸盐的 La ₂ Ti ₂ O ₇成员在加热时经历单斜向正交位移转变，如空气中 885°C (864°C–904°C) 的同步辐射衍射和 874 的中子衍射所示°C (841°C–894°C)。