Synthesis, crystal structure and microwave dielectric properties of self-temperature stable Ba1-xSrxCuSi2O6 ceramics for millimeter-wave communication

摘要

Ba_(1- x )Sr_( x )CuSi_(2)O_(6) compounds with a tetrahedral structure (I41/acd) were prepared through the solid-state reaction method. The phase building process, structural evolution and microwave dielectric properties of Ba_(1- x )Sr_( x )CuSi_(2)O_(6) were investigated. Single BaCuSi_(2)O_(6) phase can be obtained when calcined at 1050?°C for 3?h or 950?°C for 10?h. The substitution of Ba~(2+) by Sr~(2+) can effectively promote the sintering process and the maximum solubility of Ba_(1- x )Sr_( x )CuSi_(2)O_(6) was located between 0.25 and 0.30. Rietveld refinement, Raman-spectra and P-V-L complex chemical bond theory were used to explain the correlations between the crystal structures and microwave dielectric properties. The dielectric constant was dominated by the susceptibility (Σχ~(μ)) and ionic polarizability. The quality factor ( Q ?×? f ) was determined by the bond strength, packing fraction and lattice energy, especially the Si-O bond. The susceptibility of Cu-O bond and Si-O bond played an important role in controlling the temperature coefficient of the resonant frequency ( τ _( f )). A near zero τ _( f ) value was obtained at x ?=?0–0.10 and the optimum microwave dielectric properties for Ba_(1- x )Sr_( x )CuSi_(2)O_(6) were achieved at x ?=?0.20 when sintered at 1000?°C for 3?h: ε _(r)?=?8.25, Q ?×? f ?=?47616?GHz and τ _( f )?=??9.6?ppm/~(o)C.