Hai-Tao Zhou,Zhe-Nan Xu,Jian-Yun Yan,Hao Huang,Yan-Bo Guo,Kang Du,Wen-Zhong Lu,Wen Lei
In the present study, (1 − x )BaAl 2 Si 2 O 8 − x CaSnSiO 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 − x CaSnSiO 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.
Blue pigments and blue glazes play crucial roles in our daily life. Ongoing research into blue pigments aims at environmentally friendly compositions with a lower cost. In this work, Co-doped BaAl2Si2O8 pigments were synthesized by a solid-state method. The blue color of the pigments is due to the 4A2(4F) → 4T1(4P) transitions allowed by doped Co2+ in the tetrahedral coordination of the structure. The pigments exhibit excellent stability under both acidic and alkaline conditions. When combined with transparent glazes, BaAl2–xCoxSi2O8 demonstrates satisfied compatibility, resulting in blue glazes with a significant reduction in Co content compared with existing formulations. Furthermore, BaAl2–xCoxSi2O8 blue glazes possess a simple production route, commendable color performance, and cost-effectiveness.
Crystallization plays a critical role in realizing the functionalization of glass materials . However, it is imperative to understand the microscopic mechanism of both the formation and the phase transitions of nanocrystals during heat processes. Here, in the as-prepared SiO 2 -Al 2 O 3 -BaF 2 -Na 2 O glass, we studied the polymorphic phase transition of BaAl 2 Si 2 O 8 during heating-cooling circles, and a novel reversible transformation is found by serendipity. Using differential scanning calorimetry (DSC), we observed an endothermic event around 1047 K during heating at 20 K/min to 1173 K, and an exotherm event at 1024 K during the subsequent cooling. Based on the X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM), the reversible process was attributed to the transition between two morphs of BaAlF 5 nano-crystal. Na 2 O introduced in the studied glass system promotes the transformation between hexacelsian (Hexagonal) and celsian (Monoclinic). The results also show the formation of different types of crystals, such as, BaF 2 , Na 5 Al 3 F 14 and BaAlF 5 etc.
危险品化学品经营许可证（带存储）