Phase analysis and microwave dielectric properties of BaO–Nd2O3–5TiO2 composite ceramics using variable size TiO2 reagents

There are significant inconsistencies in published literature surrounding the phase analysis and physical properties of ceramics with the nominal composition BaO–Nd2O3–5TiO2 (BNT125). A careful phase analysis investigation of BNT125 ceramics using variable size TiO2 reagents was therefore undertaken using XRD, FESEM and EPMA with corresponding dielectric properties characterised over 2–3 GHz. Three distinct phases were consistently formed: Ba6−3xNd8+2xTi18O54 (x ∼ 0.67), Ba2Ti9O20 and TiO2. The use of nano-scale TiO2 reagents significantly reduced porosity and improved the dielectric properties of the composite ceramics, while markedly reducing processing times. Structural and crystal chemical indications as to the origin of this system's physical properties are discussed, with these results providing new insights into optimisation paths for microwave dielectric materials of this type.