Optimised phase compositions and achieved ultra-high Q×f values in Ca(2+y)Sn2Al(2+x)O(9+1.5x+y) ceramics by composition modulation

Abstract

The optimization of phase compositions and microwave dielectric properties in Ca(2+y)Sn2Al(2+x)O(9+1.5x + y) (−0.2 ≤ x ≤ 0.2, −0.2 ≤ y ≤ 0.2) ceramics were investigated. The change in Al content could inhibit the SnO2 second phase of Ca2Sn2Al2O9 ceramic, and the Al deficiency in Ca2Sn2Al(2+x)O(9+1.5x) (−0.2 ≤ x < 0) ceramics contributed to the increase in the content of the CaSnO3 second phase. The enrichment of the Al content could not inhibit the CaSnO3 second phase, and the low content of the CaSnO3 second phase was obtained in Ca2Sn2Al(2+x)O(9+1.5x) (0 < x ≤ 0.2) ceramics. The high content of CaSnO3 second phase was also observed in Ca(2+y)Sn2Al2O(9+y) (0 < y ≤ 0.2) ceramics, and the enrichment of Ca induced the CaSnO3 second phase. Moreover, the slight Ca deficiency inhibited the SnO2 and CaSnO3 second phases, and the Ca2Sn2Al2O9 single-phase ceramic was obtained in Ca(2+y)Sn2Al2O(9+y) (y = −0.1). The Ca(2+y)Sn2Al(2+x)O(9+1.5x + y) (−0.2 ≤ x ≤ 0.2, −0.2 ≤ y ≤ 0.2) ceramics with a high content of CaSnO3 second phases exhibited high εr and moderate Q × f values, which were controlled by the ρrel and the content of the CaSnO3 second phase, respectively. The Q × f value was sensitive to the second phases, and Ca-deficient Ca(2+y)Sn2Al2O(9+y) (y = −0.1) ceramic with Ca2Sn2Al2O9 single-phase composition exhibited the ultra-high Q × f value (Q × f = 121818 GHz at 11.86 GHz).