Ce和Ca共掺杂BaTiO_3陶瓷的结构和介电性质研究

Study on Structure and Dielectric Properties of Ce and Ca Co-Doped BaTiO_3 Ceramics

通过X射线衍射(XRD)、拉曼光谱(RS)、扫描电子显微镜(SEM)、电子顺磁共振(EPR)和介电测试技术研究了Ce和Ca共掺杂BaTiO_3陶瓷的结构、价态、位占据和介电性质。Ba/Ti比例有效的影响了陶瓷的结构。所有陶瓷样品中Ce离子不能以Ce^(4+)完全并入Ti位,或以Ce^(3+)完全并入Ba位。当Ba/Ti=1,(Ba_(1-x)Ca_x)(Ti_(0.95)Ce_(0.05))O_3(x=0.05)陶瓷形成单相四方结构,具有Ba位(Ca^(2+)/Ce^(3+))和Ti位(Ca^(2+)/Ce^(4+))混合价态的双位占据,缺陷复合体Ca^(2+)-Ce^(4+)形成。CeCa_5A(Ba/Ti=0.937)陶瓷为单相立方结构,展现一级相变的介电行为,室温附近具有非常高的介电常数(ε′=16000)。

The structure, valence states, site occupations and dielectric properties of Ce and Ca co-doped BaTiO3ceramics were studied using X-ray diffraction （XRD）, Raman spectroscopy, scanning electron microscopy （SEM）,electron paramagnetic resonance （EPR） and dielectric measurements. The Ba/Ti ratio has effects on ceramic structure.Ce ions in all samples cannot incorporate completely into Ti sites as Ce4＋ or occupy Ba sites completely as Ce3＋. WhenBa/Ti=l, the nominal （Bal_xCax）（Ti0.95Ce0.05）O3 （x=0.05） ceramic has a single-phase tetragonal perovskite structure,with the site occupations of mixed Ca2＋/Ce3＋ at Ba sites and Ca2＋/Ce4＋ at Ti sites, and the formation of Ca2＋-Ce4＋defect complexes. CeCasA （Ba/Ti=0.937） ceramic has a single-phase cubic structure, and shows a first-order phasetransition （FPT） dielectric behavior and a very high dielectric constant （ε =16000） near room temperature.