Dielectric relaxations in fine-grained SrTiO3 ceramics with Cu and Nb co-doping. Issue 8 (1st June 2019)

• Record Type: Journal Article
• Authors: Liu, Junwei; Liu, Qiaoli; Nie, Zepeng; Nie, Sheng; Lu, Dayong; Zhu, Pinwen
• Is Part Of: Ceramics international. Volume 45:Issue 8(2019)
• Page Start: 10334
• Page End: 10341
• Publication Date: 2019-06-01
• Subjects: Variable-range-hopping conduction -- Polaron dielectric relaxation -- Jahn-teller effect -- Mixed valence; Ceramics -- Periodicals; Céramique industrielle -- Périodiques; Ceramics; Periodicals; Electronic journals; 666
• DOI: 10.1016/j.ceramint.2019.02.089
• Languages: English
• ISSNs: 0272-8842

Abstract

Abstract: SrTi1−3 x (Cu x Nb2 x )O3 ( x = 0.05, 0.1, 0.15 and 0.2) ceramics were synthesized using a solid-state reaction method at 1400 °C in air. Their structures, valence states, conduction mechanisms and dielectric properties were investigated in detail. Fine grains and vibration modes of the samples related to the doping effects were observed. A distorted pseudo-cubic structure was confirmed by XRD and Raman spectroscopy. All ceramics exhibited a colossal dielectric constant and dielectric relaxations. The dielectric constant in the low- and high-frequency ranges for x = 0.05 and 0.1 was ascribed to the contribution of the grain boundary and grain, respectively, and the electrode polarization was significant at x = 0.15 and 0.2. The dielectric relaxation peaks obeyed the T −1/4 law at low temperature for all samples, confirming the polaron relaxation process. The electric modulus analysis confirmed that low-temperature dielectric relaxation was related to the grain response, and the electric conduction exhibited the same behavior with the dielectric relaxation. The variable-range-hopping conduction indicated a highly distorted structure and the localization of carriers in SrTi1−3 x (Cu x Nb2 x )O3, which was consistent with the XRD and Raman results. The mixed-valence structure of Cu was identified by XPS, and the polaron hopping between the mixed-valence Cu ions was supposed to be responsible for the dielectric relaxation and electric conduction.