Compositional Design of Multi-Cation α-SiAlON Ceramics Containing Calcium

Abstract

It was found by our previous work [1] that for Ca--SiAlON composition (Ca x Si 12-3x Al 3x O n N 16-x ) about 70% of Ca ++ in nominal composition entered into -SiAlON structure with the remainder in grain boundary. By half Ca ++ replaced by Mg ++ in multi-cation Ca,Mg--SiAlON compositions, the results indicated that the cell dimensions of Ca,Mg--SiAlON phase were obviously smaller than that of Ca--SiAlON with the same compositions. EDAX analysis further revealed that the Ca ++ contents in the grains were much higher than Mg ++ and the average value of Ca ++ contents could be close to the one in nominal composition, implying that more active cation, Ca ++ , could be incorporated into -SiAlON structure in multi-cation -SiAlONs case. Based on the above results, -SiAlON ceramics, in which Ca ++ was partly replaced by La +++ has been designed. The lattice parameters of the -SiAlONs, in which 30%Ca ++ were replaced by La +++ as additives, were close to the ones of single-cation Ca--SiAlON under the same compositions, indicating that most of Ca ++ were incorporated in -SiAlON because almost no La +++ was detected by EDS analysis of -SiAlON grains. The advantage of using additives Ca ++ combined with La +++ to form -SiAlON was expected because of high refractory of glassy grain boundary containing lanthanum. Consequently,The flexural strength of one composition of Ca ++ /La +++ doped -SiAlON ceramics at 1250°C reached as high as 555MPa was obtained, whose value was 20% higher than that at room temperature.

Performance analysis of baseband signal processing technology for 300GHz terahertz communication

“…Research in this field primarily emphasizes modulation, demodulation, and coding techniques. [1][2][3][4] THz communication combines certain characteristics of millimeter-wave and free-space laser communication, allowing for the selection and optimization of modulation modes based on those commonly used in millimeter-wave and free-space laser communication. 5,6 Among them, 2FSK modulation provides strong antinoise and anti-attenuation performance, with a simple composition circuit that is relatively easier to implement.…”