Electron paramagnetic resonance and optical absorption study of V4+ centres in YVO4 crystals
Electron paramagnetic resonance and optical absorption study of V4+ centres in YVO4 crystals
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DOI：
10.1088/0953-8984/16/39/040
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发表时间：
2004-10
期刊：
影响因子：
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通讯作者：
N Y Garces;K T Stevens;G. Foundos;L. Halliburton
中科院分区：
文献类型：
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作者：
N Y Garces;K T Stevens;G. Foundos;L. Halliburton
电子顺磁共振（EPR）已被用来表征三个不同的V4+中心在未掺杂的直拉法生长的原钒酸钇（YVO 4）晶体。这些EPR信号是在低温下观察到的，它们在相邻的51 V超精细线之间的平均c轴分裂为40 G，123 G和140 G。我们将这些中心分别称为[V4+]A、[V4+]B和[V4+]C。[V4+]A和[V4+]B中心存在于生长的晶体中。在77 K下暴露于电离辐射（X射线或紫外线激光束）会破坏这些中心并产生[V4+]C中心。晶体的生长状态在恢复到室温时恢复。角依赖数据被用来确定每个中心的g张量和51 V超精细张量的主值和主方向。我们认为[V ~（4+）]A中心是与氧空位相邻的V ~（4+）离子，[V ~（4+）]B中心是V ~（4+）离子取代Y ~（3+）离子（即钒反位缺陷）。[V4+]C中心被分配到一个V4+离子在一个常规的钒网站附近的稳定缺陷，可能是一个Zr 4+的Y3+网站。在生长的晶体中，[V4+]A中心的数量与宽的近边光学吸收带的强度（在380 nm处）之间存在相关性。这个带现在与氧空位有关，使YVO 4呈现“黄色”外观。
Electron paramagnetic resonance (EPR) has been used to characterize three distinct V4+ centres in undoped Czochralski-grown yttrium orthovanadate (YVO4) crystals. These EPR signals are observed at low temperatures, and their average c-axis splittings between adjacent 51V hyperfine lines are 40 G, 123 G, and 140 G. We refer to these centres as [V4+]A, [V4+]B, and [V4+]C, respectively. The [V4+]A and [V4+]B centres are present in as-grown crystals. Exposure at 77 K to ionizing radiation (x-rays or an ultraviolet laser beam) destroys these centres and creates the [V4+]C centres. The as-grown state of the crystal is restored upon returning to room temperature. Angular dependence data are used to determine the principal values and principal directions of the g tensor and the 51V hyperfine tensor for each of the centres. We suggest that the [V4+]A centre is a V4+ ion adjacent to an oxygen vacancy and that the [V4+]B centre is a V4+ ion substituting for a Y3+ ion (i.e. a vanadium antisite defect). The [V4+]C centre is assigned to a V4+ ion at a regular vanadium site with a nearby stabilizing defect, possibly a Zr4+ on a Y3+ site. In as-grown crystals, there is a correlation between the number of [V4+]A centres and the intensity (at 380 nm) of a broad near-edge optical absorption band. This band, now associated with oxygen vacancies, gives YVO4 a ‘yellow’ appearance.