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

In the present work, a series of (1-x)Ba 0.6 Sr 0.4 La 4 Ti 4 O 15 -xCaTiO 3 (x = 0.02, 0.03, 0.05, 0.1 and 0.2, BSLT-CT) functional ceramics were synthesized via co-firing the mixtures of Ba 0.6 Sr 0.4 La 4 Ti 4 O 15 and CaTiO 3 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 CaTiO 3 content. Raman spectra uncover O h symmetry deviation and distortions of oxygen octahedra. The variation of the CaTiO 3 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 ( V O • • $V_O^{••}$ ), namely involving in-grain and across-grain relaxation. The increase of CaTiO 3 prompts the increase of oxygen vacancy concentration, which may induce microwave loss. At x = 0.2, the microwave dielectric properties of specimens are ε r  = 47.1, Q  ×  f  = 41,200 GHz and τ f  = −5.3 ppm/°C, respectively.