School of Chemistry and EaStCHEM, University of St Andrews, St Andrews, KY16 9ST, UK.
Inorg Chem. 2013 Aug 5;52(15):8872-80. doi: 10.1021/ic401061t. Epub 2013 Jul 16.
The system Li(x)Na(1-x)NbO3 has been studied by using a combination of X-ray and neutron powder diffraction and (23)Na solid-state NMR spectroscopy. For x = 0.05 we confirm a single polar orthorhombic phase. For 0.08 ≤ x ≤ 0.20 phase mixtures of this orthorhombic phase, together with a rhombohedral phase, isostructural with the low-temperature ferroelectric polymorph of NaNbO3, are observed. The relative fractions of these two phases are shown to be critically dependent on synthetic conditions: the rhombohedral phase is favored by higher annealing temperatures and rapid cooling. We also observe that the orthorhombic phase transforms slowly to the rhombohedral phase on standing in air at ambient temperature. For 0.25 ≤ x ≤ 0.90 two rhombohedral phases coexist, one Na-rich and the other Li-rich. In this region the phase behavior is independent of reaction conditions.
采用 X 射线和中子粉末衍射以及 (23)Na 固态 NMR 光谱学研究了 Li(x)Na(1-x)NbO3 体系。对于 x = 0.05，我们确认存在单一的极性正交相。对于 0.08 ≤ x ≤ 0.20，观察到这种正交相与低温铁电多晶型 NaNbO3 同构的菱形相的相混合物。这两种相的相对分数被证明严重依赖于合成条件：菱形相在较高的退火温度和快速冷却下更有利。我们还观察到，在室温下在空气中静置时，正交相缓慢地向菱形相转变。对于 0.25 ≤ x ≤ 0.90，共存着两种菱形相，一种富钠，另一种富锂。在该区域，相行为与反应条件无关。
