Optimized sintering behavior and microwave dielectric properties of Ca_1+2xSnSi_2x+yO_3+6x+2y by composition modulation

Abstract

Microwave dielectric ceramics have played an important role in modern wireless communication systems, such as resonators, capacitors, and filters. 1-3 With the increase in communication frequency, microwave dielectric ceramics with low permittivity (ε r < 15), high-quality factor (Q × f), and near-zero temperature coefficient of resonant frequency (-10 ppm/°C ≤ τ f ≤ +10 ppm/°C) have attracted the attention of many researchers. Microwave dielectric ceramics with low ε r and high Q × f values mainly include: silicates, 2-8 germanates, 9-13 vanadates, 14-18 and stannates. 19-25 The Q × f value of stannates (Ca 2 SnO 4 19 and Li 2 O-MgO-SnO 2 24,25) exceed 100,000 GHz, and high Q × f value is necessary to improve frequency selectivity. We first reported the Ca 2 SnO 4 ceramic with excellent microwave dielectric properties (ε r = 9.9, Q × f = 120,100 GHz, and τ f =-45.6 ppm/°C). 19 The Ca 2 SnO 4 ceramic exhibited orthorhombic crystal with Pbam space group, and the CaSnO 3 phase always existed in the preparation of Ca 2 SnO 4 ceramic through stoichiometric composition. The CaSnO 3 phase can be prioritized for synthesis in the CaO-SnO 2 system. However, the cylindrical CaSnO 3 ceramic could not be obtained through traditional solid-state reaction because of a

Correlation between structural characteristics and microwave dielectric properties of walstromite BaCa2M3O9 (M = Si, Ge) ceramics

“…In general, the high content of SiO 4 tetrahedra corresponds to low ε r for microwave dielectric ceramics. Silicates with low permittivity include M O–SiO 2 ( M = Ba, Ca, Zn, Mg), 15–20 M O– N O–SiO 2 ( M = Ba, Sr, Ca; N = Zn, Mg, Co, Cu), 21–30 M O– N 2 O 3 –SiO 2 ( M = Ba, Ca; N = Al, Y, RE ), 5,31–37 and CaO– M O 2 –SiO 2 ( M = Sn, Zr, Hf) 38–46 . The low cost, absence of variable valence elements, and environmental friendliness of microwave dielectric ceramics should be considered for applications.…”

“…Silicates with low permittivity include MO-SiO 2 (M = Ba, Ca, Zn, Mg), [15][16][17][18][19][20] MO-NO-SiO 2 (M = Ba, Sr, Ca; N = Zn, Mg, Co, Cu), [21][22][23][24][25][26][27][28][29][30] MO-N 2 O 3 -SiO 2 (M = Ba, Ca; N = Al, Y, RE), 5,[31][32][33][34][35][36][37] and CaO-MO 2 -SiO 2 (M = Sn, Zr, Hf). [38][39][40][41][42][43][44][45][46] The low cost, absence of variable valence elements, and environmental friendliness of microwave dielectric ceramics should be considered for applications. Therefore, lowpermittivity silicates with variable valence elements and expensive raw materials are unsuitable for commercial production.…”

Evolution of Phase Transformation on Microwave Dielectric Properties of BaSixO1+2x Ceramics and Their Temperature-Stable LTCC Materials

“…The Si-O bond was also strong because it is approximately 55% covalent and 45% ionic [15][16][17]. Barium silicates with high contents of SiO 4 tetrahedra and Si-O bonds demonstrated their low permittivity (ε r < 15) and high-quality factor (Q × f ), which attracted considerable attention regarding microwave dielectric materials [18][19][20][21][22]. However, 13 crystalline phases were known in the BaO-SiO 2 system [23], which indicates that the complex phase compositions might exist in barium silicates.…”