Dielectric properties of Ba_(1-x)La_xTi_(1-x/4)O_3 ceramics with different La~(3+) content

摘要

In the present research n-doped BaTiO_3 compositions, with lanthanum contents x=0, 0.1, 0.3 and 0.5mol% were prepared by the free sintering method, at temperature T=1350°C for 2 h. The EDS investigations showed that samples exhibited conservation of stoichiometry according to the chemical composition formula. Morphology of the ceramic material was observed by scanning electron microscopy, whereas the crystalline structure was studied by X-ray diffraction method. Influence of La~(3+) doping on dielectric properties of Ba_(1-x)La_xTi_(1-x/4)O_3 ceramics was studied in temperature range T=20-260°C, and frequency f=100Hz-1000Hz by the Precision LCR meter Agilent E4980A. The results show a decrease of T_m with lanthanum addition. The degree of diffuseness of phase transition is more pronounced for high La content, implying the existence of a composition-induced phase transition of the ceramics. Ceramics showed maximally enhanced dielectric permittivity around phase transitions, which are the phase transitions of the pure BaTiO_3.