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首页> 外文期刊>Phase Transitions >Broad-band dielectric response of 0.5Ba(Ti0.8Zr0.2)O-3-0.5(Ba0.7Ca0.3)TiO3 piezoceramics: soft and central mode behaviour
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Broad-band dielectric response of 0.5Ba(Ti0.8Zr0.2)O-3-0.5(Ba0.7Ca0.3)TiO3 piezoceramics: soft and central mode behaviour

机译：0.5Ba（Ti0.8Zr0.2）O-3-0.5（Ba0.7Ca0.3）TiO3压电陶瓷的宽带介电响应：软模式和中心模式行为

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摘要

Dielectric properties of 0.5Ba(Ti0.8Zr0.2)O-3-0.5(Ba0.7Ca0.3)TiO3 ceramics were probed in the frequency range from 10Hz to 100 THz in a broad temperature range (10-900 K). Polar soft phonon observed in infrared spectra softens with cooling; however, below 500 K, its frequency becomes temperature independent. Simultaneously, a central mode activates in terahertz and microwave spectra; and it actually drives the ferroelectric phase transitions. Consequently, the phase transitions strongly resemble a crossover between the displacive and order-disorder type. The central mode vanishes below 200K. The dielectric relaxation in the radiofrequency and microwave range anomalously broadens on cooling below T-C1, resulting in the nearly frequency independent dielectric loss below 200K. This broadening comes from a broad frequency distribution of ferroelectric domain wall vibrations. Raman spectra reveal new phonons below 400K, i.e. already 15K above T-C1. Several weak modes are detected in the paraelectric phase up to 500K in Raman spectra. Activation of these modes is ascribed to the presence of polar nanoclusters in the material.
机译：在10Hz至100THz的频率范围内（10-900 K）范围内探查了0.5Ba（Ti0.8Zr0.2）O-3-0.5（Ba0.7Ca0.3）TiO3陶瓷的介电性能。红外光谱中观察到的极性软声子随着冷却而软化;但是，低于500 K时，其频率与温度无关。同时，中心模式会激活太赫兹和微波光谱。它实际上驱动了铁电相变。因此，相变非常类似于置换型和有序无序型之间的交叉。中央模式在200K以下消失。在T-C1以下冷却时，射频和微波范围内的介电弛豫异常扩大，导致在200K以下几乎与频率无关的介电损耗。这种扩展来自铁电畴壁振动的广泛频率分布。拉曼光谱揭示了低于400K的新声子，即已经比T-C1高出15K的声子。在顺电相中在拉曼光谱中可检测到几种弱模式，最高可达500K。这些模式的激活归因于材料中存在极性纳米团簇。

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