摘要
采用传统固相法制备了MnO2掺杂Ca0.16Sr0.04Li0.4Nd0.4TiO3微波介质陶瓷,并借助X射线衍射仪、扫描电子显微镜、网络矢量分析仪和精密阻抗分析仪对微波陶瓷的物相结构、表面形貌、介电性能和电学微结构进行了分析。结果表明掺杂MnO2部分进入Ca0.16Sr0.04Li0.4Nd0.4TiO3陶瓷晶格Ti4+位中并导致衍射主峰衍射角向高角度轻微偏移,所得陶瓷晶粒大小约5μm。随着MnO2含量的增加,观察到显著的Mn-Li氧化物杂相,过高的MnO2掺杂使得Ca0.16Sr0.04Li0.4Nd0.4TiO3陶瓷晶粒的主要生长方向由(200)变为(220)。MnO2含量的增加使得陶瓷介电常数εr从140降至122,品质因子Qf从1450显著升至1960 GHz,谐振温度系数τf较为稳定且均为40 ppm/℃左右。陶瓷内部由Li+陶瓷表面电学阻抗、晶界阻抗、晶壳和晶核形成的晶粒阻抗构成,其中晶界的电阻贡献主要来自于Li+挥发或析出形成的阳离子空位电导;晶壳和晶核电阻为电子-空穴与氧空位相互耦合形成的电导。微波陶瓷的介质损耗主要来自于晶粒区域晶核的高度半导化各构成电学微结构部件载流子束缚能力大小与活化能规律趋于一致。
Mn-doped Ca0.16Sr0.04Li0.4Nd0.4TiO3 microwave dielectric ceramics were prepared by conventional solid-state reaction method.The phases,microstructures,surface topologies,dielectric properties and electrical microstructures of the microwave ceramics were analyzed by X-ray diffractions,scanning electron microscope,vector network analyzer and precise impedance analyzer.The MnO2 dopant partly enters into crystal lattice of Ca0.16Sr0.04Li0.4Nd0.4TiO3 for substitution of Ti^4＋ ions and urges the slight shift of main diffraction peak toward high angles.The average grain sizes of the ceramics are about5 μm.With rise of MnO2 content,the phases of Mn-Li oxides are obviously observed and over-excess addition of MnO2 makes the change of grain growth inclination from faces（ 200） to（ 220） in Ca0.16Sr0.04Li0.4Nd0.4TiO3 ceramics.The increasing MnO2 content leads to the degradation of dielectric constant（ εr）from 140 to 122,the rise of quality factor（ Qf） from 1450 GHz to 1960 GHz and the little change of temperature coefficient of resonant frequency（ τf） equal to the stable value of 40 ppm/℃.The electrical properties of Mn-doped Ca0.16Sr0.04Li0.4Nd0.4TiO3 microwave ceramics are mainly ascribed to the contribution of Li^＋ surface conduction,grain boundaries and grains divided into grain shells and grain cores,where the grain boundaries show the cation-vacancy conduction due to Li^＋ volatilization or effusion,the conduction of grain shells and grain cores come from the coupling action of electron-holes and oxygen vacancies.Impedance analysis suggests that the dielectric loss of microwave ceramics is originated from serious semiconducting of grain cores in grain regions and various electrical microstructural elements show the good agreement between the binding ability of carriers and activationenergy variations by DC bias measurement.
出处
《人工晶体学报》
EI
CAS
CSCD
北大核心
2014年第9期2224-2230,共7页
Journal of Synthetic Crystals
基金
国家自然科学基金(11464006)
广西自然科学基金(2014GXNSFBA118254)
广西信息材料重点实验室研究基金(1210908-209-Z
1210908-05-Z
1210908-207-Z)
