铁电晶体Ba_(1-x)Ca_(x)TiO_(3)的能带、态密度和光学性质理论研究

Theoretical study on energy bands,density of states and optical properties of ferroelectric crystal Ba_(1-x)Ca_(x)TiO_(3)

铁电晶体BaTiO_(3)已经被广泛应用于介电和压电元件领域中,但BaTiO_(3)存在多个相变温度,尤其是发生在室温附近的相变,会严重损害晶体质量。为了对BaTiO_(3)的性能进行改良,考虑对BaTiO_(3)晶体进行掺杂。基于第一性原理,计算了不同Ca含量掺杂BaTiO_(3)的电子结构和光学性质,即Ba_(1-x)Ca_(x)TiO_(3)(x=0,0.125,0.25,0.5)。通过研究发现,在电子结构方面,BaTiO_(3)是直接带隙半导体,其禁带宽度为1.74 eV,掺杂Ca导致BaTiO_(3)带隙增加。BaTiO_(3)掺杂Ca后的态密度比未掺杂的BaTiO_(3)大,但随着掺杂含量的增加,态密度不断减小。在光学性质方面,BaTiO_(3)掺杂Ca后,导致介电峰发生明显偏移。BaTiO_(3)掺杂Ca后,其静态介电常数变小。不同Ca含量掺杂BaTiO_(3)后对不同波长的光吸收有所不同,当Ca含量为0.125时,对光的吸收能力下降程度较大。本文对Ba_(1-x)Ca_(x)TiO_(3)(x=0,0.125,0.25,0.5)的研究结果表明其在光电领域具有广泛的应用前景,同时对该系列晶体的生长及性能研究提供一定的理论基础。

BaTiO_(3)crystals have been widely used in the field of dielectric and piezoelectric components,but BaTiO_(3)has multiple phase transition temperatures,especially at room temperature,which will seriously damage the crystal quality.In order to improve the properties of BaTiO_(3),doping BaTiO_(3)crystals is considered.In this paper,based on first-principle calculation,the electronic structure and optical properties of BaTiO_(3)doped with different Ca contents,namely Ba_(1-x)Ca_(x)TiO_(3)(x=0,0.125,0.25,0.5),were calculated.It is found that BaTiO_(3)is a direct band gap semiconductor in terms of electronic structure,and its band gap width is 1.74 eV.Doping Ca leads to an increase in the band gap of BaTiO_(3).The density of states of BaTiO_(3)doped with Ca is larger than that of undoped BaTiO_(3),but the density of states decreases with the increase of doping content.In terms of optical properties,BaTiO_(3)doping with Ca results in a significant shift in the dielectric peak.After BaTiO_(3)is doped with Ca,its static dielectric constant becomes smaller.The light absorption of different wavelengths is different after BaTiO_(3)is doped with different Ca contents.When Ca is 0.125,the light absorption capacity decreases greatly.The research results of Ba_(1-x)Ca_(x)TiO_(3)(x=0,0.125,0.25,0.5)crystals in this paper show a broad application prospects in the field of optoelectronics and provide a theoretical basis for the growth and properties of this series of crystals as well.