Low-loss (1-x)Ba0.6Sr0.4La4Ti4O15-xCaTiO3 microwave dielectric ceramics with medium permittivity

• Published in: Journal of alloys and compounds 2020-04, Vol.819, p.153011, Article 153011
• Main Authors: Zhang, Xiaohua, Chang, Ning, Zhang, Jie, Zhou, Yuanyuan, Yue, Zhenxing, Li, Longtu
• Format: Article
• Language: English
• Subjects: Calcium titanate; Ceramics; Crystal defects; Crystal structure; Defects; Depolarization; Dielectric properties; Electroceramics; Hexagonal perovskite; Hexagonal phase; Microwave dielectric properties; Microwave frequencies; Oxygen; Perovskite structure; Perovskites; Raman spectra; Vacancies
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2019.153011

In the present work, a series of (1-x)Ba0.6Sr0.4La4Ti4O15-xCaTiO3 (x = 0.02, 0.03, 0.05, 0.1 and 0.2, BSLT-CT) functional ceramics were synthesized via co-firing the mixtures of Ba0.6Sr0.4La4Ti4O15 and CaTiO3 powders. Crystal structure and microwave dielectric properties were investigated together thermally stimulated depolarization currents (TSDC). Scanning electron microscopy (SEM) would be explored. X-ray diffraction confirms that these compounds display a single hexagonal phase with perovskite structure and the diffraction peaks shift to high angles with increasing CaTiO3 content. Raman spectra uncover Oh symmetry deviation and distortions of oxygen octahedra. The variation of the CaTiO3 addition has a direct impact on the dielectric properties of the (1-x)BSLT-xCT ceramics at microwave frequency. TSDC was conducted to acquire the defects associated with extrinsic microwave loss mechanism. The main type of defect in BSLT-CT is oxygen vacancy (VO••), namely involving in-grain and across-grain relaxation. The increase of CaTiO3 prompts the increase of oxygen vacancy concentration, which may induce microwave loss. At x = 0.2, the microwave dielectric properties of specimens are εr = 47.1, Q × f = 41,200 GHz and τf = −5.3 ppm/°C, respectively. •New solid solutions of Ba0.6Sr0.4La4Ti4O15–CaTiO3 are successfully obtained.•Excellent microwave properties have been harvested.•TSDC provides new insight to comprehend defects and extrinsic loss.•Oxygen vacancies don't dominate the Q × f values in BSLT-CT compounds.