| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1490380 | Materials Research Bulletin | 2012 | 5 Pages |
The origins of microwave dielectric properties (1 − x)CaTiO3–x(Li0.5La0.5)TiO3 (0.2 ≤ x ≤ 0.8) ceramics, prepared by a conventional solid-state reaction method, were investigated based on the theory of bond valence. The XRD and SEM results showed that complete solid solutions with orthorhombic perovskite structure were formed in the whole investigated compositional range. The dielectric constant (ɛr), quality factor (Q × f) and temperature coefficient of resonant frequency (τf) were closely related to B-site, A-site and the difference between A-site and B-site bond valences of ABO3 perovskite compounds, respectively. As x value increased from 0.2 to 0.8, the dielectric constant increased from 198.3 to 276.8, the Q × f value decreased from 4340 to 1880 GHz, and the τf value varied from +489.7 to −178 ppm/°C. For practical applications, excellent microwave dielectric properties of ɛr = 245, Q × f = 2750 GHz and τf = +0.75 ppm/°C were obtained for 0.4CaTiO3–0.6(Li0.5La0.5)TiO3 ceramics.
Graphical abstractThis picture shows that the variation in A-site bond valence will affect the Q × f value. A smaller A-site bond valence indicates that the bond strength between oxygen and A-site cation is weaker and the anharmonic interaction is increased, so the Q × f value is decreased.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► CaTiO3–(Li0.5La0.5)TiO3 ceramics were prepared by solid-state reaction method. ► Origins of microwave dielectric properties were analyzed via bond valence theory. ► XRD result indicates that solid solutions are formed in the present system. ► The composition of x = 0.6 shows a near-zero τf (0.75 ppm/°C) for practical use.
