Phase transformation and dielectric characteristics in Ba0.85Ca0.15Ti1−x(Mg1/2W1/2)xO3 ceramics

• Published in: The Journal of physics and chemistry of solids 2014-06, Vol.75 (6), p.782-786
• Main Authors: Zhang, Jingji, Liu, Bei, Ji, Ludong, Wang, Jiangying, Zhai, Jiwei
• Format: Article
• Language: English
• Subjects: C. Raman spectroscopy; D. Crystal structure
• ISSN: 0022-3697; 1879-2553
• DOI: 10.1016/j.jpcs.2014.01.023

Structure, phase transformation and dielectric properties of Ba0.85Ca0.15Ti1−x(Mg1/2W1/2)xO3 ceramics with 0.02≤x≤0.20 have been investigated by means of X-ray diffraction, Raman and dielectric spectroscopy. X-ray diffraction and Raman results show that (Mg1/2W1/2)4+ substitution for Ti4+ ions results in the formation of a second phase of BaWO4 at x=0.05. Dielectric measurements reveal a gradual transformation from normal ferroelectric characteristics to typical relaxor behaviour. A more reasonable relationship f=f0exp[−(Ea/kBTm)p] is introduced to characterise the dielectric relaxation, which yields an activation energy with ~27meV. The high activation energy for the composition with a high (Mg1/2W1/2)4+ level may be ascribed to more defect pair [mgTi׳׳−V0׳׳]. •(Mg1/2W1/2)4+ substitution for Ti4+ ions results in the formation of a second phase of BaWO4 at x=0.05 and a structural change from a tetragonal phase to a cubic one.•A gradual change from normal ferroelectric characteristics to typical relaxor behaviour is observed.•The dielectric relaxation is modelled using the Vogel–Fulcher relationship with a dozen meV.•The high activation energy for high substitution level may be ascribed to more defect pair [mgTi׳׳−V0׳׳].