Microwave dielectric ceramics in the system BaO–Li2O–Nd2O3–TiO2 |
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Authors: | A Silva F Azough R Freer C Leach |
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Affiliation: | Manchester Materials Science Centre, Grosvenor Street, Manchester M1 7S, UK |
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Abstract: | Ceramics in the system BaO-Li2O–Nd2O3–TiO2 (BNT–LNT) were prepared by the mixed oxide route. Powders were mixed, milled, calcined and sintered at 1475°C for 4 h. Fired densities decreased steadily along the series from BNT to LNT. The microstructures of samples rich in BNT were dominated by small needle-like grains; the LNT samples comprised larger (6 μm) cubic grains. X-ray diffraction showed that there was a transition from orthorhombic BNT to cubic LNT; small amounts of LNT could be accommodated in BNT, but between 10–20% LNT there was the development of the second phase. Small additions of LNT led to a small increase in relative permittivity, but decreased the dielectric Q-value (from the maximum of 1819 at 4 GHz). As BNT and LNT exhibit negative and positive temperature dependencies of permittivity respectively, the addition of 10–20% LNT to BNT should yield samples with zero temperature dependence of r Impedance spectroscopy showed that data could only be acquired at elevated temperatures for BNT rich samples (above 500°C), but at modest temperatures (less than 100°C) for the more conductive LNT. |
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Keywords: | BaO–Li2O–Nd2O3–TiO2 Electron microscopy Impedance spectroscopy Microwave dielectric ceramics |
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