Phase compositions and crystal structure of Sn-deficient Ca2Sn2Al2O9 microwave dielectric ceramics with high Q×f values

摘要

? 2022The phase compositions and microwave dielectric properties of Sn-deficient Ca2Sn2Al2O9 ceramics in this study were explored. The CaSnO3 and SnO2 second phases existed at Ca2Sn2-xAl2O9-2x (x = 0) ceramic. Single-phase Ca2Sn2Al2O9 ceramics were obtained at 0.08 ≤ x ≤ 0.1, and the orthorhombic structure with the Pbcn space group of Ca2Sn2Al2O9 was verified. For multi-phase Ca2Sn2-xAl2O9-2x (0 ≤ x ≤ 0.06) ceramics, their microwave dielectric properties were mainly affected by second phase contents, and their Q × f values increased gradually with the rise in x. High Q × f (105,700 GHz at 12.99 GHz) was obtained by the Ca2Sn2-xAl2O9-2x (x = 0.08) ceramic with high intrinsic Q × f (175,000 GHz). The large deviation between measured Q × f values and fitted intrinsic Q × f values could be ascribed to the Sn4+ vacancies of the Sn-deficient Ca2Sn2Al2O9 ceramics. The Ca2Sn2-xAl2O9-2x (0 ≤ x ≤ 0.1) ceramics presented large negative τf values, and this τf was mainly affected by τε. Meanwhile, the Ca2Sn2-xAl2O9-2x (x = 0.08) ceramic achieved optimal microwave dielectric properties (εr = 8.3, Q × f = 105,700 GHz at 12.99 GHz and τf = ?63.7 ppm/°C), indicating the good feature of this material for millimetre-wave applications.