Temperature‐stable BaAl₂Si₂O₈–CaSnSiO₅ microwave dielectric ceramics

Abstract

In the present study, (1 − x)BaAl 2 Si 2 O 8 −xCaSnSiO 5 −y wt.% LiF microwave dielectric ceramics were prepared through the traditional solid-state sintering at 950−1395 • C for 5 h. The BaAl 2 Si 2 O 8 phase could coexist with the CaSnSiO 5 phase at (1 − x)BaAl 2 Si 2 O 8 −xCaSnSiO 5 (.2 ≤ x ≤ .6) ceramics, and no other secondary phase was observed. The CaSnSiO 5 , as a τ f regulator, adjusted the negative τ f value of BaAl 2 Si 2 O 8 to near zero. Excellent microwave dielectric properties (ε r = 8.1, Q × f = 37 560 GHz, and τ f = −1.5 ppm/ • C) were obtained from the 0.6BaAl 2 Si 2 O 8 −0.4CaSnSiO 5 ceramic. The sintering temperature of 0.6BaAl 2 Si 2 O 8 −0.4CaSnSiO 5 ceramic decreased from 1375 • C to 950 • C by introducing 2 wt.% LiF. The 0.6BaAl 2 Si 2 O 8 −0.4CaSnSiO 5 −2 wt% LiF ceramic exhibited remarkable microwave dielectric properties (ε r = 7.6, Q × f = 17 420 GHz, and τ f = −12.2 ppm/ • C) and could be applied to the low-temperature co-fired ceramic (LTCC) field. K E Y W O R D S (1 -x)BaAl 2 Si 2 O 8 −xCaSnSiO 5 ceramic, LTCC applications, microwave dielectric properties, phase transition 1 480

Microwave dielectric properties of tetragonal scheelite‐structured (NaY)1/2MoO4 ceramics

“…In order to achieve the goal of near-zero TCF values, as a common and effective method, chemical compatible substances with opposite TCF values are selected and mixed. [19][20][21] According to crystal chemistry theory, solid solutions could be obtained and the dielectric constant and TCF value could be tailored to satisfy the demands of microwave devices and components by ion substitution or combination of two kinds Mo-based ABO 4 compounds with similar structure, such as (1-x)(Na 0.5 La 0.5 )MoO 4 -x(Na 0.5 Bi 0.5 )MoO 4 22 and K 0.5 (Nd 1-x Bi x ) 0.5 MoO 4 system. 23 Dielectric properties could be modified by ion replacements forming solid solutions, which is a quite common and effective method to improve the physical properties of scheelite structured systems.…”

“…However, due to the large TCF values, their performances in practical applications were unstable. In order to achieve the goal of near‐zero TCF values, as a common and effective method, chemical compatible substances with opposite TCF values are selected and mixed 19–21 . According to crystal chemistry theory, solid solutions could be obtained and the dielectric constant and TCF value could be tailored to satisfy the demands of microwave devices and components by ion substitution or combination of two kinds Mo‐based ABO 4 compounds with similar structure, such as (1‐x)(Na 0.5 La 0.5 )MoO 4 ‐x(Na 0.5 Bi 0.5 )MoO 4 22 and K 0.5 (Nd 1‐x Bi x ) 0.5 MoO 4 system 23 .…”