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Solid solutions of (1−x)BaTiO3–xBi(Mg2/3Nb1/3)O3 (0 ≤ x ≤ 0.6) were prepared via a standard mixed‐oxide solid‐state sintering route and investigated for potential use in high‐temperature capacitor applications. Samples with 0.4 ≤ x ≤ 0.6 showed a temperature independent plateau in permittivity (εr). Optimum properties were obtained for x = 0.5 which exhibited a broad and stable relative εr ~940 ± 15% from ~25°C to 550°C with a loss tangent <0.025 from 74°C to 455°C. The resistivity of samples increased with increasing Bi(Mg2/3Nb1/3)O3 concentration. The activation energies of the bulk were observed to increase from 1.18 to 2.25 eV with an increase in x from 0 to 0.6. These ceramics exhibited excellent temperature stable dielectric properties and are promising candidates for high‐temperature multilayer ceramic capacitors for automotive applications.

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Ceramists are constantly looking for materials to be used as dielectric resonators in the telecommunication industry. These applications require materials with ∊r ∼ 4 – 120, Q × f0 > 10 000 GHz and τf ∼ 0 ppm K−1. Additionally, efforts are also underway to lower the sintering temperatures (e. g. ≤ 800 °C) to reduce processing and electrode costs. The simultaneous achievement of all the three properties mentioned above is difficult; nevertheless, some materials have been synthesized fulfilling the criteria for microwave applications. This study is an overview of various studies on materials for possible applications as microwave dielectrics and factors affecting their microwave properties. These factors include crystal structure, defects, fabrication route, and the type and concentration of substituents and additives.

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0.5BaTiO3–(0.5 − x)BiMg1/2Ti1/2O3−xNaNbO3 (x = 0.10–0.30) ceramics were processed via a conventional solid state sintering route. X-ray diffraction analysis and Raman spectroscopy showed the formation of a cubic perovskite structure. Microstructural analysis of the samples revealed densely packed grains. The addition of NaNbO3 resulted in the enhancement in dielectric properties as a function of temperature. Relative permittivity decreased from 850 to 564 (at room temperature) with an increase in x; however, the stability in dielectric properties was improved with an increase in NaNbO3 concentration. At x = 0.25, relative permittivity (εr) was ~630 ± 15% in a temperature range of −70–220 °C with low dielectric loss (tanδ) < 0.025 (−57 to 350 °C) and high recoverable energy density ~0.55 J/cm3 which meet the criterion for X9R MLCC applications.