Far-infrared, Raman spectroscopy, and microwave dielectric properties of La(Mg0.5Ti(0.5-x)Snx)O3 ceramics
Far-infrared, Raman spectroscopy, and microwave dielectric properties of La(Mg0.5Ti(0.5-x)Snx)O3 ceramics
复制标题
DOI：
10.1063/1.2778743
复制
发表时间：
2007-09-15
影响因子：
3.2
通讯作者：
Liu, Hsiang-Lin
中科院分区：
文献类型：
--
作者：
Babu, G. Santosh;Subramanian, V.;Liu, Hsiang-Lin
采用固相反应法制备了组分为（x=0.0-0.5）的La(Mg0.5Ti(0.5-x)Snx)O-3钙钛矿陶瓷。通过x射线衍射、远红外反射率、拉曼光谱和微波介电性能对陶瓷进行了表征。陶瓷具有单斜对称性，具有P2(1)/n空间群。通过对四参数半量子模型的反射率拟合，估计了本征介电常数和损耗。计算了横向光学声子模强度和平均声子阻尼。在拉曼光谱中确定了与b位有序相对应的模式，并通过假设两种合并模式分析了La(MgTi)(0.5)O-3的A（1g）模式。长程阶的变化与A（1g）模的全宽半最大值有关。微波测量在8-10 GHz的频率范围内进行。随着锡浓度的增加，介电常数（epsilon(')）从28.4逐渐降低到19.7，而谐振频率温度系数（tau(f)）从-68降低到-84 ppm/℃。La(MgTi)(0.5)O-3的质量因子与谐振频率（Qxf）的乘积为55,000 GHz，当x=0.25时，该乘积降至46,000，而La(MgSn)(0.5)O-3的质量因子与谐振频率（Qxf）的乘积增加到63,000 GHz。
La(Mg0.5Ti(0.5-x)Snx)O-3 perovskite ceramics with composition (x=0.0-0.5) are prepared by the solid state reaction method. The ceramics are characterized by x-ray diffraction, far-infrared reflectance, Raman spectroscopy, and microwave dielectric properties. The symmetry of ceramics is monoclinic with P2(1)/n space group. Intrinsic dielectric constant and loss are estimated by fitting reflectance to the four-parameter semiquantum model. Transverse optic phonon mode strengths and average phonon damping are calculated. The modes corresponding to B-site ordering are identified in Raman spectra and the A(1g) mode of La(MgTi)(0.5)O-3 is analyzed by assuming two merging modes. The variation of long-range order is correlated with full width half maximum of the A(1g) mode. Microwave measurements are carried out in the frequency range of 8-10 GHz. The dielectric constant (epsilon(')) is found to gradually decrease from 28.4 to 19.7 with an increase in tin concentration, whereas the temperature coefficient of resonant frequency (tau(f)) decreases from -68 to -84 ppm/degrees C. The product of the quality factor and resonant frequency (Qxf) obtained for La(MgTi)(0.5)O-3 is 55,000 GHz, that decreases to 46,000 for x=0.25 composition and then increases to 63,000 GHz for La(MgSn)(0.5)O-3.