DIELECTRIC PROPERTIES OF SINGLE-CRYSTALS OF AL2O3 AND AL2O3 DOPED WITH CHROMIUM OR VANADIUM
DIELECTRIC PROPERTIES OF SINGLE-CRYSTALS OF AL2O3 AND AL2O3 DOPED WITH CHROMIUM OR VANADIUM
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DOI：
10.1002/pssa.2210270237
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发表时间：
1975-01-01
期刊：
影响因子：
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通讯作者：
RAO, KV
中科院分区：
文献类型：
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作者：
GOVINDA, S;RAO, KV
测量了Al_2O_3、Al_2O_3：Cr(0.03和2m ol%)和Al_2O_3：V(2m o l%)单晶的介电常数(K)、损耗(tanδ)和电导率(σ)随频率的变化，频率范围为102~107 Hz，温度为30~450℃(电场始终垂直于光轴)。在30℃时，Al_2O_3的K值为9.4，且与频率无关。掺铬或掺钒不会使Al_2O_3的K值发生明显变化。在该频率范围内，所有这些样品在30°C时的介电损耗都低于检测水平(tanδ<；0.0005)。在这些晶体中，介电常数随着温度的升高而增加，表现出约200°C的频率依赖关系；在较低的频率下，随温度的变化更大(介电损耗也表现出类似的行为)。K的这种行为归因于晶体缺陷引起的空间电荷极化。这些晶体在不同频率下的对数σ与1/Ta的曲线不一致，表明在这个温度区域内的电导是由杂质引起的。计算出上述固体在高温区的电导激活能分别为0.77、0.69、0.64和0.62 eV。掺杂晶体中较低的电导激活能值可能归因于晶体中较大的载流子浓度(与Al_2O_3相比)。
Dielectric constant (K), loss (tan δ), and conductivity (σ) of single crystals of Al2O3, Al2O3: Cr (0.03 and 2 mol%) and Al2O3:V (2 mol%) have been measured as a function of frequency in the range 102to 107Hz and at temperatures between 30 and 450 °C, (where the electric field is always perpendicular to the optic axis). TheKvalue of Al2O3, at 30 °C is 9.4 and frequency‐independent. Doping by chromium or vanadium produces no detectable change in theKvalue of Al2O3. The dielectric loss of all these samples at 30 °C is below detection level (tan δ < 0.0005) throughout this frequency region. In these crystals, the dielectric constant increases with temperature exhibiting a frequency dependence from about 200 °C; the changes inKwith temperature being larger at lower frequencies (similar behaviour is exhibited by the dielectric loss). This behaviour ofKis attributed to space charge polarisation due to crystal defects. The plots of log σ vs. 1/Tat different frequencies for these crystals do not coincide indicating the conduction in this temperature region is due to impurities. The activation energies for conduction — in the high temperature region — are calculated to be 0.77, 0.69, 0.64, and 0.62 eV respectively for the above mentioned solids. The lower activation energy values for conduction in doped crystals may be attributed to a larger charge carrier concentration in them (compared to Al2O3).