Crystal structure, lattice vibration and microwave dielectric properties of 3CaO•2SiO2•xCaF2 (0 ≤ x ≤ 1.5) ceramics

The crystal structure, lattice vibration and microwave dielectric properties of 3CaO center dot 2SiO(2)center dot xCaF(2) ceramics were investigated in this work. With the increasing of x value, the crystal structure of 3CaO center dot 2SiO(2)center dot xCaF(2) ceramics transfers from rankinite (Ca3Si2O7) to cuspidine (Ca4Si2O7F2). The increase of the vibration energy and shrinkage of [SiO4] tetrahedral unit hampers the ionic polarization and thus reduces relative permittivity (epsilon(r)). The enlarged FWHM of the Si-O stretching peak reflects a more drastic anharmonic lattice vibration, resulting in a lower quality factor (Q x f value). The Raman shift of O/F-Ca-O/F bending peak is positively correlated with the temperature coefficient of resonant frequency (tau(f)). The microwave dielectric properties of epsilon(r) and Q x f value (-@11 GHz) ranging from 7.89 to 8.42, and 21805-46098 GHz, respectively. The stable complex permittivity (epsilon(center dot)(r)) in the frequency range of 20-110 GHz indicates that the fluoride cuspidine ceramics could be a promising candidate for microwave device applications.

Automated summary

This study investigated the crystal structure, lattice vibration, and microwave dielectric properties of 3CaO·2SiO(2)·xCaF(2) ceramics. The crystal structure of the ceramics changed from rankinite to cuspidine with increasing x value. The increase in vibration energy and shrinkage of the SiO4 tetrahedral unit resulted in a decrease in relative permittivity. The stable complex permittivity in the microwave frequency range suggests that these ceramics could be promising for microwave device applications.