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Comparative study of phase structure and dielectric properties for K0.5Bi0.5TiO3[BOND]BiAlO3 and LaAlO3[BOND]BiAlO3



In this work, two perovskite-type compounds, K0.5Bi0.5TiO3 and LaAlO3, have been selected as host material to incorporate with BiAlO3 using a solid-state reaction route. The phase evolution and dielectric properties for both systems have been investigated in detail. For the K0.5Bi0.5TiO3[BOND]BiAlO3 system, it is interesting to find that when using Bi2O3, Al2O3, K2CO3, and TiO2 as starting materials, the formed compounds are K0.5Bi0.5TiO3[BOND]K0.5Bi4.5Ti4O15 and Al2O3 only plays a dopant role. There are two distinct dielectric peaks appearing in the patterns of temperature dependence of dielectric constant, corresponding to the phase-transition points of perovskite-type K0.5Bi0.5TiO3 and Aurivillius-type K0.5Bi4.5Ti4O15, independently. In comparison, using Bi2O3, Al2O3, and La2O3 as starting materials, the pure perovskite phase LaAlO3[BOND]BiAlO3 can be obtained. Compared to the inherent paraelectric behavior in LaAlO3, the diffuse phase-transition phenomena can be observed in the LaAlO3[BOND]BiAlO3 binary system, which corresponds well to the Vogel–Fulcher (VF) relationship. Moreover, compared to pure LaAlO3, the synthesized LaAlO3[BOND]BiAlO3 compound shows enhanced dielectric properties, which are promising in application as gate dielectric materials.