PT基弛豫铁电体结构与性能的研究
发布时间：2018-08-05 18:20
【摘要】：本论文从钛酸铅(PT)基弛豫铁电体的结构与性能的关系出发,研究了铌镁酸铅-钛酸铅(PMN-PT)和铌钪酸铅-铌镁酸铅-钛酸铅(PSN-PMN-PT)弛豫铁电体的微观组织形貌以及介电、压电和铁电性能。采用改进的两步前躯体合成法制备一系列不同组分配比的PSN-PMN-PT三元铁电陶瓷,研究了烧结温度和PSN含量对陶瓷微观结构、致密性和电学性能的影响。随着烧结温度升高,陶瓷的相结构保持不变,始终为三方-四方两相共存的钙钛矿结构。晶粒尺寸不断增大,致密度先增大后减小,当烧结温度为1140℃,致密度达到最大(为理论密度的98.26%)。扫描电子显微镜(SEM)显示,当烧结温度为1140℃时,气孔率最小且晶粒尺寸均匀,微结构致密。综上,最佳烧结温度为1140℃。PSN固溶量的增加几乎不影响PSN-PMN-PT陶瓷的相结构和晶粒尺寸,所有陶瓷仍为三方-四方相共存的钙钛矿结构。随着PSN含量从5%增加45%,陶瓷的居里温度Tc明显提高,从154.9℃增加到235.6℃；但介电、压电及铁电性能降低。在众多组分中,25PSN-38PMN-37PT组分表现出良好的综合性能：压电常数d33～478 pC/N、机电耦合系数kp～65.1%、最大介电常数εm～8338、介电损耗tan δ-0.03、剩余极化强度Pr～19.2μc/cm2、矫顽场Ec～9.5kV/cm.居里温度Tc～192.2℃。PMN-PT铁电单晶电畴观察发现,极化样品中出现许多不同取向的小畴带,且畴带尺寸不同。不同取向小畴带的形成很好的解释了PMN-PT铁电单晶高的压电常数d33～1500pC/N以及压电常数的不均匀性。然而,未极化的样品除了部分小区域存在小畴带外,大部分区域看不见畴带。随着温度的升高,在三四方相变点附近Trt～89℃,未极化样品中迅速出现沿特定方向生长的条带状电畴。降温过程中,相变点附近形成不同取向的小畴,这可能归因于铁电畴内部极性微区的相互作用。极性微区的存在解释了PMN-PT铁电体的弛豫特性。相比于PMN-PT单晶,三元PSN-PMN-PT铁电单晶表现出更加优异的性能：居里温度Tc～170℃,室温介电常数εrt高达4714,剩余极化强度Pr～37.11μC/cm2,同时表现出了较大的矫顽场Ec～4.74kV/cm。电畴观察分析表明,随着温度升高,不规则波浪型电畴逐渐演变为平直条带状直到消光变黑。铁电-顺电的相变发生在一个较宽的温度范围(160～180℃),暗示了相变的弛豫特性,这与介电温谱相一致。
[Abstract]:Based on the relationship between structure and properties of (PT) based relaxor ferroelectrics, the microstructure and dielectric properties of lead magnesium niobate lead titanate (PMN-PT) and lead scandium niobate lead magnesium niobate lead titanate (PSN-PMN-PT) relaxor ferroelectrics were studied in this paper. Piezoelectric and ferroelectric properties. A series of PSN-PMN-PT ternary ferroelectric ceramics with different distribution ratios were prepared by a modified two-step precursor synthesis method. The effects of sintering temperature and PSN content on the microstructure, densification and electrical properties of the ceramics were studied. With the increase of sintering temperature, the phase structure of the ceramics remains unchanged, and it is always a perovskite structure in which the tetragonal and the rhombohedral phases coexist. With the increasing of grain size, the density increases first and then decreases. When the sintering temperature is 1140 鈩，
本文编号：2166606
[Abstract]:Based on the relationship between structure and properties of (PT) based relaxor ferroelectrics, the microstructure and dielectric properties of lead magnesium niobate lead titanate (PMN-PT) and lead scandium niobate lead magnesium niobate lead titanate (PSN-PMN-PT) relaxor ferroelectrics were studied in this paper. Piezoelectric and ferroelectric properties. A series of PSN-PMN-PT ternary ferroelectric ceramics with different distribution ratios were prepared by a modified two-step precursor synthesis method. The effects of sintering temperature and PSN content on the microstructure, densification and electrical properties of the ceramics were studied. With the increase of sintering temperature, the phase structure of the ceramics remains unchanged, and it is always a perovskite structure in which the tetragonal and the rhombohedral phases coexist. With the increasing of grain size, the density increases first and then decreases. When the sintering temperature is 1140 鈩，
本文编号：2166606
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