AGe 4 O 9 (A = Ba, Sr) ceramics with hexagonal structure were fabricated by solid-phase reaction. BaGe 4 O 9 sintered at 1060 °C had low ε r ∼9.8, high Q × f ∼78,400 GHz and τ f ∼ -44.2 ppm/°C, whilst SrGe 4 O 9 sintered at 1100 °C exhibited relatively high ε r ∼11.2, low Q × f ∼62,500 GHz and near-zero τ f ∼ -11.7 ppm/°C. The τ f of SrGe 4 O 9 was nearer to zero than that of BaGe 4 O 9 due to the smaller τ ε value and the smaller distortion of the [GeO 6 ] octahedrons. The ‘rattling’ cations at A-site contribute to comparatively high ε r , low Q × f and near-zero τ f values in Sr 1- x Ba x Ge 4 O 9 ceramics. This work presents a new idea of adjusting the microwave dielectric performance (MDP) of ceramics by changing the strength of the rattling effect at A-site.
T 1 –T 2 multi-modality submicron particles were widely used in clinic imaging, biochemical analysis and biosensor. Here, we prepared a new magnetic submicron particle through the spatial-gap of cellulose nanocrystal (CNC) dispersion as a template.The obtained submicron particles were ellipsoid and had a better magnetic response and relaxation effects. By varying the Fe(acac) 3 to Gd(acac) 3 ratio, it was possible to tune the surface morphology, crystal structure and T 1 –T 2 relaxation effect. More importantly, the pre-drying and burning process had influence on the polycrystalline growth process of Fe(acac) 3 and Gd(acac) 3 mixture, and the slow removal process for the CNC template could endow the compounds with different relaxation effects. By using the spatial-gap of the cellulose nanocrystal dispersion as a template makes it possible to fabricate T 1 –T 2 multi-modality crystalline submicron particles directly and is promising for preparing other CNC-templating based functional materials.
危险品化学品经营许可证（带存储）