0.7Pb(Mg_(1/3)Nb_(2/3))O_3-0.3PbTiO_3薄膜中自极化效应诱导的稳定热释电系数

采用sol-gel方法在Pt/Ti/SiO_2/Si衬底上制备了0.7Pb(Mg_(1/3)Nb_(2/3))O_3-0.3PbTiO_3,并研究了其铁电和热释电性质.X射线衍射结果表明薄膜具有高度的(111)择优取向.结果显示,在没有任何极化处理情况下,薄膜具有稳定的热释电系数,达到1.58×10~(-8) Ccm~(-2)K~(-1).当极化电场高于3倍薄膜的矫顽电场时,薄膜的热释电系数几乎保持不变.撤掉极化电场后,薄膜的热释电系数在10天后仅仅衰减4%左右,远比PZT薄膜稳定.研究发现不同方向极化处理,薄膜的热释电电流具有非对称性,即正向极化时热释电电流随电场增加而增大,负方向极化处理时,热释电电流随电场增加而减小.这些结果显示0.7Pb(Mg_(1/3)Nb_(2/3))O_3-0.3PbTiO_3表现出的优异热释电特性起源于薄膜中的自极化效应.

Stable pyroelectric coefficient induced from self-polarization in sol-gel derived 0.7Pb(Mg_(1/3)Nb_(2/3))O_3-0.3PbTiO_(3) thin films

Ferroelectric and pyroelectric properties of 0.7Pb(Mg_(1/3)Nb_(2/3))O_3-0.3PbTiO_3 thin fill deposited on Pt/Ti/SiO_2/Si substrates using a sol-gel method were investigated. X-ray diffraction results showed that the fills were highly (111) oriented. It was found that the films show a stable pyroelectric coefficient (1.58×10~(-8) Ccm~(-2)K~(-1)) without any poling processes. Nearly constant pyroelectric coefficient was obtained when the applied poling dc bias field increased to greater than three times of its coercive field. The pyroelectric coefficient of the poled 0.7Pb(Mg_(1/3)Nb_(2/3))O_(3)-0.3PbTiO_3 thin film capacitor dropped to 96% of its initial value after ten days, which was much more stable than that of PZT samples. Asymmetric pyroelectric currents were found in the 0.7Pb(Mg_(1/3)Nb_(2/3))O_3-0.3PbTiO_3 thin films with different poling directions. For pos-itive poling, pyroelectric current increased with the poling electric field. In the case of negative poling, pyroelectric current decreased with the poling electric field. These results suggest that the good pyroelectric properties of the 0.7Pb (Mg_(1/3)Nb_(2/3))O_3-0.3PbTiO_3 thin films could be due to the presence of self-polarization in this material.