Crystal structure and specific heat of calcium lanthanide oxyborates Ca4LnO(BO3)3

IF 0.9 4区材料科学 Q3 CRYSTALLOGRAPHY

Zeitschrift Fur Kristallographie-Crystalline Materials Pub Date : 2022-08-22 DOI:10.1515/zkri-2022-0029

Nicola D. Kelly, S. Savvin, S. Dutton

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引用次数: 1

Abstract

Abstract Calcium lanthanide oxyborates Ca4LnO(BO3)3 are of interest for their optical and electromechanical properties. Their crystal structure has been well characterised using powder and single-crystal X-ray diffraction but there remains some disagreement regarding cation ordering in these compounds. In this study, combined X-ray and neutron powder diffraction was employed to study the cation distribution and obtain accurate boron and oxygen atomic coordinates for six Ca4LnO(BO3)3 compounds (Ln = Pr, Nd, Tb, Ho, Er, Yb) at room temperature and one (Ln = Tb) at 50 and 1.5 K. All compounds adopt the previously reported monoclinic structure with space group Cm. The Ln3+ ions are disordered over two of the three metal sites, with the extent of disorder increasing across the lanthanide series with decreasing ionic radius. Low-temperature neutron data for Ca4TbO(BO3)3 showed a decrease in paramagnetic scattering on cooling but no obvious magnetic Bragg or diffuse scattering at the lowest temperature of 1.5 K. We report specific heat data at cryogenic temperatures for eight Ca4LnO(BO3)3 compounds and relate the magnetic properties of these compounds to their structural behaviour.

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氧化硼酸镧系钙Ca4LnO(BO3)3的晶体结构和比热

摘要镧系元素氧硼酸盐Ca4LnO（BO3）3因其光学和机电性能而备受关注。使用粉末和单晶X射线衍射已经很好地表征了它们的晶体结构，但在这些化合物中的阳离子有序性方面仍存在一些分歧。本研究采用X射线和中子粉末衍射相结合的方法研究了六种Ca4LnO（BO3）3化合物（Ln=Pr，Nd，Tb，Ho，Er，Yb）在室温下的阳离子分布，并获得了精确的硼和氧原子坐标。Ln3+离子在三个金属位点中的两个上是无序的，随着离子半径的减小，整个镧系的无序程度增加。Ca4TbO（BO3）3的低温中子数据显示，冷却时顺磁散射减少，但在1.5K的最低温度下没有明显的磁布拉格或扩散散射。

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来源期刊

Zeitschrift Fur Kristallographie-Crystalline Materials CRYSTALLOGRAPHY-

CiteScore

2.00

自引率

16.70%

发文量

期刊介绍： Zeitschrift für Kristallographie – Crystalline Materials was founded in 1877 by Paul von Groth and is today one of the world’s oldest scientific journals. It offers a place for researchers to present results of their theoretical experimental crystallographic studies. The journal presents significant results on structures and on properties of organic/inorganic substances with crystalline character, periodically ordered, modulated or quasicrystalline on static and dynamic phenomena applying the various methods of diffraction, spectroscopy and microscopy.