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<p>Hard sodium lithium niobate (LNN) solid solutions offer a promising environmentally benign alternative to lead-based ferroelectric materials for electronic devices. A major challenge in their practical application is that their ferroelectric phase relaxes over a timescale ranging from weeks to years to an orthorhombic phase, limiting their long-term performance. In order to understand the structural changes in the relaxation process, high mechanical quality factor Li<sub><i>x</i></sub>Na<sub>1−<i>x</i></sub>NbO<sub>3</sub> solid-solutions were deliberately stored under ambient conditions for 24 months, without any specialized hermetic protection, to assess their stability over time. We utilized 1D and 2D&#xa0;<sup>23</sup>Na solid-state Nuclear Magnetic Resonance (ssNMR) to investigate short-range structural changes in the 24-months-old aged and unaged Li<sub><i>x</i></sub>Na<sub>1−<i>x</i></sub>NbO<sub>3</sub> solid-solutions. NMR results reveal a system with phase-changes as a function of aging time and temperature. The samples exhibit a multiphase structure compromised of crystalline R and Q orthorhombic domains, along with two types of amorphous regions. A significant amount of ferroelectric phase persists in the ceramics after 24 months of exposure to ambient conditions. A structural model based on short-range order of sodium was suggested and agrees well with the lattice parameter of the freshly prepared samples.</p>

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Structural relaxation of ferroelectric phase in hard sodium lithium niobate solid solutions studied by solid-state NMR

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年8月21日

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  • Millena Logrado,
  • Changhao Zhao,
  • Hergen Breitzke,
  • Jürgen Rödel,
  • Gerd Buntkowsky

摘要

Hard sodium lithium niobate (LNN) solid solutions offer a promising environmentally benign alternative to lead-based ferroelectric materials for electronic devices. A major challenge in their practical application is that their ferroelectric phase relaxes over a timescale ranging from weeks to years to an orthorhombic phase, limiting their long-term performance. In order to understand the structural changes in the relaxation process, high mechanical quality factor LixNa1−xNbO3 solid-solutions were deliberately stored under ambient conditions for 24 months, without any specialized hermetic protection, to assess their stability over time. We utilized 1D and 2D 23Na solid-state Nuclear Magnetic Resonance (ssNMR) to investigate short-range structural changes in the 24-months-old aged and unaged LixNa1−xNbO3 solid-solutions. NMR results reveal a system with phase-changes as a function of aging time and temperature. The samples exhibit a multiphase structure compromised of crystalline R and Q orthorhombic domains, along with two types of amorphous regions. A significant amount of ferroelectric phase persists in the ceramics after 24 months of exposure to ambient conditions. A structural model based on short-range order of sodium was suggested and agrees well with the lattice parameter of the freshly prepared samples.