A nonlinear thermodynamic theory is used to investigate the phase structures, polarization and pyroelectric properties of polydomain epitaxial Ba_0.6Sr_0.4TiO₃ thin films. Polydomain $a_1$/$a_2$/$a_1$/$a_2$, $c{a}_1$/$c{a}_2$/$c{a}_1$/$c{a}_2$, $a{a}_1$/$a{a}_2$/$a{a}_1$/$a{a}_2$, $r_1$/$r_2$/$r_1$/$r_2$ phases and single domain tetragonal $c$, paraelectric $PE$ phases have been found in the misfit strain-temperature phase diagram. Note that the polydomain phases are found to be more complicated than single domain phases, which also leads to the variability of pyroelectric properties. The results of pyroelectric coefficients reveal that a distinguished in-plane and out-of-plane pyroelectric response appears near the phase boundaries of $a_1$/$a_2$/$a_1$/$a_2$-$PE$ and $c{a}_1$/$c{a}_2$/$c{a}_1$/$c{a}_2$-$c$, $c$-$PE$, respectively, in which the pyroelectric coefficients $\left|p_i\right|$ are larger than 0.6 $\mu$C/cm²K, exceeding most experimental and theoretical values. It is found that the maximum in-plane and out-of-plane pyroelectric coefficients occur under the strain of 0.23% and -0.225% at room temperature, respectively. The giant pyroelectric performance of polydomain Ba_0.6Sr_0.4TiO₃ thin films may provide potential to highly sensitive infrared detectors.

利用非线性热力学理论研究了多畴外延Ba _0.6 Sr _0.4 TiO ₃薄膜的相结构，极化和热电性质。多域${\mathrm{一种}}_{\mathrm{1个}}$/${\mathrm{一种}}_2$/${\mathrm{一种}}_{\mathrm{1个}}$/${\mathrm{一种}}_2$， $C{\mathrm{一种}}_{\mathrm{1个}}$/$C{\mathrm{一种}}_2$/$C{\mathrm{一种}}_{\mathrm{1个}}$/$C{\mathrm{一种}}_2$， $\mathrm{一种}{\mathrm{一种}}_{\mathrm{1个}}$/$\mathrm{一种}{\mathrm{一种}}_2$/$\mathrm{一种}{\mathrm{一种}}_{\mathrm{1个}}$/$\mathrm{一种}{\mathrm{一种}}_2$， ${\mathrm{[R}}_{\mathrm{1个}}$/${\mathrm{[R}}_2$/${\mathrm{[R}}_{\mathrm{1个}}$/${\mathrm{[R}}_2$ 相和单畴四方 $C$，顺电 $PË$在失配应变-温度相图中已找到相。注意，发现多畴相比单畴相更复杂，这也导致热电性质的可变性。热电系数的结果表明，在热电势的相界附近出现了明显的面内和面外热电响应。${\mathrm{一种}}_{\mathrm{1个}}$/${\mathrm{一种}}_2$/${\mathrm{一种}}_{\mathrm{1个}}$/${\mathrm{一种}}_2$--$PË$ 和 $C{\mathrm{一种}}_{\mathrm{1个}}$/$C{\mathrm{一种}}_2$/$C{\mathrm{一种}}_{\mathrm{1个}}$/$C{\mathrm{一种}}_2$--$C$， $C$--$PË$分别表示其中的热电系数 $\left|p_{\mathrm{一世}}\right|$ 大于0.6 $\mu$C / cm ² K，超过大多数实验和理论值。发现在室温下最大平面内和平面外热电系数分别在0.23％和-0.225％的应变下发生。多畴Ba _0.6 Sr _0.4 TiO ₃薄膜的巨大热电性能可能为高灵敏度的红外探测器提供潜力。