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(K, Na)NbO3(KNN)基无铅压电陶瓷具有较高的居里温度和优异的综合性能,被认为是替代铅基压电陶瓷的重要候选材料之一。为进一步提升其性能,研究者们采用元素掺杂等方法进行优化。Mn元素的化学改性机理在常压烧结的KNN陶瓷中被广泛研究,然而,掺杂后的KNN陶瓷致密度差异明显,从而给解析Mn元素掺杂改性的物理化学机制带来挑战。本工作以热压烧结制备的KNN陶瓷为研究对象,系统探究Mn掺杂对热压烧结的KNN陶瓷微观结构及电学性能的影响。结果表明,所制备的陶瓷均具有高的致密度,相对密度超过98%,且Mn掺杂并未改变KNN的相结构。同时Mn掺杂后材料依然保持了较高的压电性能,当掺杂量为1.5%(摩尔分数)时,d33达到106 pC/N,剩余极化提高至15 μC/cm2;而PFM微观畴翻转测试表明,随着Mn掺杂量的增加,铁电畴的局域翻转电压逐渐提升,陶瓷机械品质因数Qm提高到175,表现出“硬性”掺杂效应。上述结果表明,Mn掺杂在热压烧结制备的KNN陶瓷中展现出与传统掺杂机制所不同的Qm和Pr同时提升、d33保持在较高值的非典型“硬性”掺杂效应。本研究为理解Mn掺杂对KNN的作用机制提供了新的视角,并为无铅压电陶瓷的设计与优化提供参考。
Abstract：Introduction(K, Na)NbO3(KNN)-based lead-free piezoelectric ceramics are considered to be one of the important candidates to replace lead-based piezoelectric ceramics due to their high Curie temperature and excellent comprehensive performance. To further improve its performance, the strategy of element doping is employed. The doping behavior of the Mn element in pressure-sintered KNN ceramics has been extensively studied. However, there are significant differences in the density of Mn-doped KNN ceramics in different works, which poses a challenge to the analysis of the underlying mechanism of Mn doping and its modification effect. Therefore, this study takes hot-pressed KNN ceramics as the research object due to their high densification, and systematically explores the impact of Mn doping on the microstructure and electrical properties of KNN ceramics. Methods In this study, KNN ceramics with MnO2 doping were prepared by hot-pressed sintering. The specific composition is(K0.5Na0.5)NbO3–x% MnO2(abbreviated as KNN–x% MnO2, x = 0, 0.5, 1.0, 1.5). The raw materials include K_2CO3(99.0%), Na_2CO3(99.8%), Nb_2O5(99.99%), and MnO2(98.8%), all of which were purchased from Sinopharm Chemical Reagent Co., Ltd. First, carbonate and Nb_2O5 were placed in a nylon ball mill with zirconia balls according to the formula ratio, and ball milled for 24 h using anhydrous ethanol as the medium; the ball-milled slurry was dried and calcined at 730 ℃ for 4 h, and then ball-milled again and calcined again at 930 ℃ for 4 hours. Subsequently, different amounts of MnO2 were added to the calcined powder, mixed and ball-milled for 24 h, and then dried and ground to obtain Mn-doped KNN ceramic powder. Finally, the ceramic block was prepared by hot pressing and sintering at 950 ℃ and 30 MPa for 2 h under argon atmosphere. After cutting, grinding, and annealing at different temperatures, the sample surfaces were subsequently coated with silver electrode for electrical measurements. The poling process was performed at 3.5 kV/mm in 120 ℃ silicone oil for 30 min. The surface micromorphology of the ceramics was characterized by Merlin scanning electron microscope(SEM). The crystal structure was analyzed by D/Max 2500 X-ray diffractometer(XRD). The density of the samples was measured using the Archimedean drainage method. The dielectric properties were tested using a TH2827 impedance analyzer. The ferroelectric properties were obtained using a TF Analyzer 2000 ferroelectric analyzer. The piezoelectric constant d33 was measured using a ZJ–3A quasi-static d33 tester. The mechanical quality factor Qm was measured using a TH2839 impedance analyzer. The local domain structure and domain switching behavior were tested and analyzed using an MFP–3D atomic force microscope with piezoelectric force microscopy(PFM). Results and discussion High-density(relative density > 98%) KNN–x% MnO2 ceramics were successfully prepared by hot pressing sintering process. XRD results show that MnO2 doping does not change the perovskite phase structure of KNN. With the increase of Mn doping amount, the Pr of the ceramic shows a trend of first increasing and then slightly decreasing. At x = 1.0–1.5%, Pr reaches 14.92–18.32 μC/cm2, d33 can reach up to 106 pC/N, and both positive and negative strains are improved, reflecting enhanced ferroelectric and piezoelectric responses after Mn doping. PFM test shows that the switching voltage of the local ferroelectric domain gradually increases from 5 V to 20 V, indicating that Mn doping enhances the domain wall pinning effect. At the same time, the mechanical quality factor Qm of the ceramic is significantly improved, with the highest value reaching 175, reflecting the typical "hard" doping behavior. Conclusions This study found that Mn-doped KNN ceramics exhibit an atypical "hard" doping effect for the high-density hot-pressed ceramics that is different from the traditional doping mechanism in lead-based ceramics, in which Qm and Pr are simultaneously improved and d33 is maintained at a high value. This atypical "hard" doping effect induced by Mn doping provides a new perspective for understanding the mechanism of element doping in the KNN system, and also provides significant guidance for the optimized design of high-performance lead-free piezoelectric ceramics.
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基本信息:
DOI：10.14062/j.issn.0454-5648.20240851
中图分类号:TQ174.1
引用信息:
[1]钟子晴,张乾宇,徐泽,等.Mn掺杂对热压烧结(K_(0.5)Na_(0.5))NbO_3无铅压电陶瓷电学性能的影响[J].硅酸盐学报,2025,53(09):2613-2621.DOI:10.14062/j.issn.0454-5648.20240851.
基金信息:
国家自然科学基金(52421001,52325204)
2025-08-13
2025-08-13
2025-08-13