现代探测和通讯技术的迅猛发展迫切需要高性能的微波可调谐器件，高性能的微波调谐材料是其应用的基础。具备较低介电损耗，高可调谐率，高击穿电压等优点的铁电薄膜材料钛酸锶钡（Ba_1-xSr_xTiO₃）是在该领域最具有应用前景的材料之一。然而在实际研究过程中发现介电损耗和调谐率之间是同步变化的，所以要克服两个参数之间的协同变化，获得低损耗，高调谐率的高性能薄膜仍具有挑战性。

本文基于激光脉冲沉积技术，首先在MgO(001)衬底上克服巨大的晶格失配，制备出高质量的Ba_1-xSr_xTiO₃外延薄膜。通过对其生长参数的优化，发现Ba_0.6Sr_0.4TiO₃薄膜适合在相对较高的衬底温度和相对较低的氧压下生长，且随着沉积衬底温度的升高（680~780 ℃），Ba_0.6Sr_0.4TiO₃薄膜结晶质量变高，晶粒尺寸变大，相对介电常数增加，调谐率增大。在1 MHz的测试频率下，施加30 V的直流偏压，Ba_0.6Sr_0.4TiO₃薄膜的调谐率为50.8%，品质因子为62，优值因子为31.49。其次通过改变Ba/Sr比例和优化电极结构的方式，极大提升薄膜的介电性能，最终得到调谐率为54.2%，品质因子为81，优值因子高达43.90的Ba_0.4Sr_0.6TiO₃薄膜。最后在研究Ba_1-xSr_xTiO₃薄膜介电性能的过程中，注意到在室温下处于顺电相的Ba_0.6Sr_0.4TiO₃薄膜和Ba_0.4Sr_0.6TiO₃薄膜在室温下均具有铁电性。猜测其可能是薄膜成分分布不均匀，相变扩张产生的铁电微区导致的。

高性能的Ba_1-xSr_xTiO₃薄膜在后续的器件研究以及介电损耗和调谐率协同变化原因的探索中具有基础性的意义，为Ba_1-xSr_xTiO₃薄膜在微波调谐领域的实际应用打下基础。

With the rapid development of modern detection and communication technology, high-performance microwave tunable devices are urgently needed, and high-performance microwave tunable materials are the basis of their research. Barium strontium titanate (Ba_1-xSr_xTiO₃), a ferroelectric thin film material with low dielectric loss, high tunability and high breakdown voltage, is one of the most promising materials in this field. However, during the actual study, it was found that the dielectric loss and tuning rate were synchronized. Therefore, it is still very difficult to overcome the synergistic change between the two parameters to obtain high-performance films with low loss and high tuning rate.

Based on pulsed laser deposition technology, Ba_1-xSr_xTiO₃ epitaxial films with high quality were prepared on MgO (001) substrate by overcoming the huge lattice mismatch. By optimizing its growth parameters, it is found that Ba_0.6Sr_0.4TiO₃ thin film is suitable for growing under relatively high substrate temperature and relatively low oxygen pressure. And the crystal quality, grain size, relative dielectric constant and tuning rate of Ba_0.6Sr_0.4TiO₃ become better with the increase of deposition substrate temperature (680~780 ℃). At the test frequency of 1 MHz, the tunability of Ba_0.6Sr_0.4TiO₃ film is 50.8%, the quality factor is 62, and the merit factor is 31.49. Secondly, the dielectric properties of the films were optimized by changing the Ba/Sr ratio and adjusting the electrode structure. Ba_0.4Sr_0.6TiO₃ thin films with tunability of 54.2%, quality factor of 81 and merit factor of 43.90 were obtained. Finally, in the process of studying the dielectric properties of Ba_1-xSr_xTiO₃ thin films, it is noted that Ba_0.6Sr_0.4TiO₃ thin films and Ba_0.4Sr_0.6TiO₃ thin films in paraelectric phase at room temperature have ferroelectric properties. This may be caused by the uneven distribution of thin film components and the ferroelectric microregions generated by phase transition expansion.

The high-performance Ba_1-xSr_xTiO₃ thin film is of fundamental significance in the subsequent device research and the exploration of the reasons for the cooperative change of dielectric loss and tuning rate, and also lays a foundation for the practical application of Ba_1-xSr_xTiO₃ thin film in the field of microwave tuning.