[论文解读] Physical and Dielectric Properties of Polycrystalline LaV$_{0.5}$Nb$_{0.5}$O$_4$

Ashok Kumar, Simranjot K. Sapra+4 more|arXiv (Cornell University)|Jan 22, 2026

Advancements in Solid Oxide Fuel Cells被引用 0

一句话总结

本论文分析两种烧结温度（1000°C 和 1250°C）如何影响 LaV0.5Nb0.5O4 多晶体的结构、振动行为、电子态和介电性质。

ABSTRACT

We report a detailed investigation of the structural, electronic, vibrational, and dielectric properties of polycrystalline LaV$_{0.5}$Nb$_{0.5}$O$_4$ samples, prepared at two sintering temperatures (1000\degree C and 1250\degree C). The introduction of Nb$^{5+}$ at the V$^{5+}$ site leads to notable structural and vibrational changes, which can be attributed to their isoelectronic nature and the comparatively larger ionic radius of Nb$^{5+}$. The Rietveld refinement of the X-ray diffraction patterns confirms a coexistence of monoclinic ($P$2$_{1}$/$n$) and scheelite-type tetragonal ($I$4$_{1}$/$a$) phases; for example, with a fraction of 4\% and 96\% for the sample annealed at 1250\degree C. The particle morphology has altered from spherical (1000\degree C) to irregular-shaped (1250\degree C) as a result of increase in annealing temperature. The Raman spectroscopy, Fourier Transform Infrared spectroscopy and X-ray Photoemission Spectroscopy have been used to understand the vibrational and electronic properties. An optical band gap of 2.7~eV for the sample sintered at 1250\degree C is calculated using Ultraviolet-vis diffuse reflectance spectroscopy measurements. The dielectric studies shows the higher dielectric permittivity ($ε$$_{r}$) and lower dielectric loss for the sample annealed at 1250\degree C.

研究动机与目标

• 研究 Nb5+ 在 V5+ 位点替代对 LaVO4 基正交顶钠酸盐的结构和振动特性的影响。
• 表征烧结温度对相组成和形貌的影响。
• 利用 XPS 及相关光谱方法确定电子结构与氧化态。
• 评估振动光谱（Raman、FTIR）和带隙（UV-vis DRS）及光学带隙。
• 在温度与频率的函数下评估介电介电常数与损耗。

提出的方法

• 通过常规固相法合成 LaV0.5Nb0.5O4，煅烧于 1000°C，最终烧结于 1250°C。
• 对 XRD 图谱进行 Rietveld 精炼以量化单斜相 (P2_1/n) 与钙钛矿样四方晶系 (I4_1/a) 相分数。
• 使用 FE-SEM-EDX 获取形貌与元素分布；TEM 观察微观结构与SAED；HR-TEM 观察晶格或晶面。
• 用 Raman 和 FTIR（ATR）光谱表征振动特性；用 XPS（Nb、V、La、O 核层）分析电子结构。
• 利用 Kubelka–Munk 变换和 Tauc 图从 UV-vis 漫反射光谱估算光学带隙。

Figure 1: The room temperature XRD patterns with Rietveld refinement of (a) LVNO-1000 and (b) LVNO-1250 samples. The open red circles, black solid line, and blue solid line exhibits the experimental, calculated, and the difference between experimental and calculated pattern, respectively. The vertic

实验结果

研究问题

• RQ1 Nb5+ 在 V5+ 位点的取代如何影响 LaVO4 基正交顶钠酸盐中相的稳定性及单斜与四方相的共存？
• RQ2 Nb 含量与烧结温度对振动（Raman/FTIR）和电子（XPS）特征有何变化？
• RQ3 烧结温度及由此产生的相分数如何影响 LaV0.5Nb0.5O4 的介电性质和带隙？

主要发现

• XRD 显示单斜 P2_1/n 与 scheelite 型四方 I4_1/a 相的共存；LVNO-1000 ~51% 四方、~49% 单斜，LVNO-1250 ~96% 四方、~4% 单斜。
• 形貌从 1000°C 的球形颗粒在 1250°C 时变为不规则形状且晶粒尺寸分布更宽，大温度下晶粒更大。
• UV-vis DRS 得到带隙约 ~3.2 eV（1000°C）与 ~2.7 eV（1250°C），显示四方相含量增加时带隙变窄。
• FTIR 与 Raman 谱图证实 VO4^3− 存在与 Nb 的掺入；某些模态强度随温度升高而增强，反映相变。
• XPS 确认 Nb5+、V5+、La3+ 的氧化态；La 3d 核峰呈现卫星特征及两样品之间的结合能略有偏移。
• 介电研究表明 1250°C 样品具有更高的介电常数与更低的介电损耗，归因于致密化程度提高与孔隙度降低。

Figure 2: The FE-SEM images of the LVNO-1000 sample at (a) 1 $\mu$ m, (b) 500 nm and (c) probed region of scan (at 5 $\mu$ m) with the corresponding elemental mappings of all elements; the FE-SEM images of the LVNO-1250 sample at (d) 1 $\mu$ m, (e) 500 nm and (f) probed region of scan (at 5 $\mu$ m)