The microwave dielectric loss of stoichiometric and non-stoichiometric Ba(Co1/3Nb2/3)O3 ceramics have been measured from 2-300 K in magnetic fields ranging from 0 to 5 T using a dielectric resonator (DR) technique. The microwave absorption from spin excitations of unpaired d-electrons in exchange coupled Co2+ ions dominate the loss of the Ba(Co1/3Nb2/3)O3 ceramics at cryogenic temperatures. Two peaks in the loss tangent (tan δ) versus temperature relation from a distinctly different origin occur at 25-30 K and 90 K, which increase in magnitude with increasing Co content in the bulk dielectric samples. Evidence that these peaks result from polaron conduction from hopping between Co2+ and Co3+ ions includes (1) the peak's observed temperature range, (2) the decrease in peak intensity of approximately a factor of two in a large applied magnetic fields (5 T), and (3) a strong correlation between the peak's magnitude and both the fraction of the minority Co3+ in the dominant Co2+ matrix and D.C. conductivity at elevated temperatures. A magnetic-field independent high temperature peak with a maximum at 250 K dominates the room temperature microwave loss whose magnitude correlates with those of the low temperature peaks. This suggests that the defects responsible for carrier conduction play an important role in establishing the loss tangent at room temperature. This article is protected by copyright. All rights reserved.

中文翻译：

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Ba(Co1/3 Nb2/3 )O3微波陶瓷介电损耗的起源

化学计量和非化学计量 Ba(Co1/3Nb2/3)O3 陶瓷的微波介电损耗已使用介电谐振器 (DR) 技术在 0 至 5 T 的磁场中从 2-300 K 测量。来自交换耦合 Co2+ 离子中未配对 d 电子自旋激发的微波吸收主导了 Ba(Co1/3Nb2/3)O3 陶瓷在低温下的损失。损耗角正切 (tan δ) 与温度关系的两个峰值来自明显不同的起源，出现在 25-30 K 和 90 K，随着体介质样品中 Co 含量的增加，其幅度增加。这些峰是由 Co2+ 和 Co3+ 离子之间跳跃引起的极化子传导产生的证据包括 (1) 峰的观察温度范围，(2) 在大外加磁场 (5 T) 中峰值强度降低约两倍，以及 (3) 峰值幅度与主要 Co2+ 基质中少数 Co3+ 的比例和高温下的直流电导率。与磁场无关的高温峰值在 250 K 处具有最大值，它支配着室温微波损耗，其幅度与低温峰值的幅度相关。这表明负责载流子传导的缺陷在确定室温下的损耗角正切方面起着重要作用。本文受版权保护。版权所有。高温下的导电性。与磁场无关的高温峰值在 250 K 处具有最大值，它支配着室温微波损耗，其幅度与低温峰值的幅度相关。这表明负责载流子传导的缺陷在确定室温下的损耗角正切方面起着重要作用。本文受版权保护。版权所有。高温下的导电性。与磁场无关的高温峰值在 250 K 处具有最大值，它支配着室温微波损耗，其幅度与低温峰值的幅度相关。这表明负责载流子传导的缺陷在确定室温下的损耗角正切方面起着重要作用。本文受版权保护。版权所有。