嵌埋Ni颗粒的BaTiO_3/SrTiO_3薄膜的相变特性

采用高温X射线原位衍射和变温介电谱对SrTiO3基底上外延生长的BaTiO3(嵌埋Ni颗粒)薄膜进行了相变特性分析。从X射线衍射和介电谱的分析结果得出,BaTiO3的相变温度点转变为弥散的温度区间。在这个弥散的相变温度区间内,由于基底和薄膜之间的失配,以及嵌埋Ni颗粒的应力作用,薄膜的介电响应弥散剧烈,并偏离德拜弛豫。分析Cole-Cole图获知,BaTiO3薄膜在四方相转变为立方相的相变过程中同时存在几种极化机制,在高温状态下介电损耗随温度增大而增大。降温过程中,薄膜没有立即恢复四方相,可能是基底和Ni颗粒的共同作用影响了相变弛豫。

Phase transition of BaTiO3/SrTiO3 film embedding Ni nanocrystals

This paper presents the results of high-temperature X-ray diffraction (XRD) study and temperature dependency analysis of the dielectric of BaTiO3(Ni) thin film on the SrTiO3 substrate. The results show that the phase transition temperature of a BaTiO3(Ni) thin film has a wide range. The tetragonal to cubic phase transition of BaTiO3(Ni) thin film was reversible, but the reversible phase transition didnt occur immediately after cooling process. The dielectric dispersion of BaTiO3(Ni)/SrTiO3 was caused by the stress and the mismatch between BaTiO3 thin film and the SrTiO3 substrate, and the effect of Ni nanocrystals. The dielectric relaxation was deviation from the Deby relaxation, and the dielectric loss increased with the increase of temperature. The results from the Cole-Cole plot show that the tetragonal to cubic phase transition of BaTiO3(Ni) thin film included several polarization mechanisms function. The dielectric loss increased with the increase of temperature at a high temperature. The film was not restored tetragonal phase immediately in the cooling process, which might be the combined effect of both substrate and Ni particles.