Composite thin films of 1–x [Bi_0.5Na_0.5TiO₃] – x [K_0.5Na_0.5NbO₃ + 1 wt% Gd₂O₃] (BNT–KNNG); (x = 0.01) have been deposited at various O₂ pressures from 0.1 to 10 Pa by pulsed laser deposition, and their crystal structure, surface morphology, optical, dielectric, and ferroelectric properties were investigated. X-ray diffraction analysis of thin films deposited at 0.1 Pa revealed a single phase of BNT–KNNG and further (> 0.1 Pa), film crystallinity gradually increased with a rise in O₂ pressure. The improvement in the refractive index and a reduction in optical bandgap are observed with O₂ pressure and are estimated to be 2.28–2.42 and 4.08–3.65 eV, respectively. The third-order nonlinear optical coefficients estimated using the Z-scan technique are found to be enhanced with O₂ pressure. The film deposited at 10 Pa exhibited a higher nonlinear refractive index (n₂ = 6.188 × 10^− 6 cm²/W) and a strong absorption coefficient (β = 1.043 cm/W). The temperature-dependent dielectric response displayed two structural phase transitions from rhombohedral to tetragonal phase at 165 ^oC and tetragonal to cubic phase at 298 ^oC. The enhanced dielectric (ε_r = 411, tanδ = 0.156 @ 1 kHz), Microwave dielectric (ε_r = 317 and tanδ = 0.0074 @ 10 GHz), and ferroelectric (P_r = 25.31 µC/cm², E_C = 42.62 kV/cm @ 1 kHz) properties with low leakage current are observed for the film deposited at 10 Pa which followed a space charge limited conduction behavior. The obtained microwave and nonlinear optical properties of BNT–KNNG composite films are suitable for tunable microwave and optical photonic device applications.

中文翻译：

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氧分压对BNT-KNNG复合薄膜非线性光学和电学性质的影响

1– x [Bi _0.5 Na _0.5 TiO ₃ ] – x [K _0.5 Na _0.5 NbO ₃ +1 wt％Gd ₂ O ₃ ]的复合薄膜（BNT–KNNG）；（x  = 0.01）已通过脉冲激光沉积在0.1至10 Pa的各种O ₂压力下沉积，并研究了它们的晶体结构，表面形态，光学，介电和铁电性能。沉积在0.1 Pa的薄膜的X射线衍射分析表明，BNT-KNNG具有单相态，并且进一步（> 0.1 Pa），随着O _2的增加，薄膜的结晶度逐渐增加压力。在O ₂压力下可以观察到折射率的改善和光学带隙的减少，分别为2.28–2.42和4.08–3.65 eV。发现使用Z扫描技术估计的三阶非线性光学系数会随着O ₂压力而增强。沉积在10Pa的膜显示出更高的非线性折射率（Ñ ₂ = 6.188×10 ^-第6厘米² / W）和强烈的吸光系数（β  =1.043厘米/ W）。随温度变化的介电响应在165 ^o C时显示出从菱形到四方相的两个结构相变，在298 ^o C时显示出从四面体到立方相的两个结构相变^。C.增强电介质（ε _{- [R}  = 411，黄褐色δ  = 0.156 @ 1千赫），微波介质（ε _{- [R}  = 317和黄褐色δ  = 0.0074 @ 10千兆赫），和铁电（P _{- [R} = 25.31μC/厘米²，ë对于在10 Pa处沉积的薄膜，观察到具有低泄漏电流的_C = 42.62 kV / cm @特性，并且遵循漏电限制的导电行为。BNT-KNNG复合薄膜的微波和非线性光学特性非常适合可调谐的微波和光子器件应用。