MgO·1.15Ga_(2)O_(3)陶瓷的晶体结构、振动谱及本征介电性能

Crystalline Structure,Vibrational Spectra and Intrinsic Dielectric Properties of MgO·1.15Ga_(2)O_(3) Ceramic

合成了颗粒均匀细小的单相MgO·1.15Ga_(2)O_(3)尖晶石粉体,通过无压预烧结合热等静压烧结制备出致密陶瓷。采用X射线Rietveld全谱拟合法确定其晶体结构为(Mg_(0.118)Ga_(0.882))^(IV)[Mg0.781Ga_(1.185)□_(0.033)]^(VI)O_(4)(□为空位),用Raman光谱与红外反射光谱研究了晶体结构、声子振动模与本征介电性能的关系。结果表明:MgO×1.15Ga_(2)O_(3)陶瓷的介电常数ε_(r)=13.21,品质因子Qu×f=166 THz,且[Mg—O]多面体振动基团的声子振动模对振子强度和本征介电损耗影响较大。晶格声子振动模对本征介电损耗也有不容忽视的影响。

Magnesium gallate spinel ceramic is a promising candidate material for communication system devices due to its unique microwave dielectric properties.In this work,a pure phase MgO·1.15Ga_(2)O_(3) ceramic powder with the uniform and fine particle size was synthesized via solid-state reaction.The crystal structure of synthesized powder was determined by X-ray diffraction,showing that the structure is(Mg_(0.118)Ga_(0.882))^(IV)[Mg0.781Ga_(1.185)□_(0.033)]^(VI)O_(4).The ceramic was fabricated by pressureless sintering and subsequent hot isostatic pressing sintering with the powder.Furthermore,the correlations among crystal structure,phonon mode parameters and intrinsic dielectric properties were investigated by Raman scattering spectroscopy and Fourier transform far-infrared reflection spectroscopy.The results show that MgO·1.15Ga_(2)O_(3) ceramic has good microwave dielectric properties(i.e.,dielectric constantεr of 13.21 and quality factor Qu×f of 166 THz).Besides,the[Mg—O]polyhedra vibrational group yields a larger contribution to infrared active intensity and dielectric loss rather than other vibration modes.The lattice vibration modes at low frequencies also provide a considerable contribution to intrinsic dielectric loss.