Qu Shaobo1,2, Yang Zupei3, Gao Feng3, Xue Jin, Tian Changsheng3 (1 Xi'an Jiaotong University, Xi'an 710049, China; 2 Air Force Engineering University, Xi'an 710038, China; Effect of pre-fired powder and ceramic sample phase composition, based on this The effects of potassium doping on the ordered microdomain, dielectric and electrostrictive properties of PMN-based ceramics were studied in detail. Potassium doping had little effect on the phase composition of PMN-based pre-fired powders and ceramics; theoretical calculation and Raman scattering spectrum analysis All of these show that the addition of potassium slightly reduces the size of ordered microdomains of PMN-based ceramics. The addition of potassium also slightly reduces the dielectric and electrostrictive properties of PMN-based ceramics. Finally, it is analyzed that potassium doping reduces the dielectric and electrical properties. Causes of stretchability (MgmNb) O3; Potassium doped; Ordered microdomains; Dielectric properties; Electrostrictively ordered microdomains 1 but related to ordered microdomains i mediated properties especially Ishir Pb (Mg1/3Nk/ 3) O3 (abbreviated as PMN) is a very important class of relaxation ferroelectrics, Chen et al. first proved that non-stoichiometric 1:1 ordered domains exist in PMNs by doping erbium; Annealed the PMN at 970°C for up to one week and found an orderly domain size No significant increase was further evidenced by the fact that there are indeed a large number of ordered microdomains in the PMN with a 1:1 structure, although it is recognized that there exists a 1:1 structure in the PMN that is different from the overall stoichiometric ratio is an ordered microdomain for electrostrictive properties The impact study has not reported that the solid solution Q 80PMN-.20PT (abbreviated as PMN-based ceramic) formed by O3 and PbTiO3 (referred to as PT) is the object of study, and studies the influence of potassium ions on PMN-based ceramic ordered microdomains, and the order The influence of the change in micro-dimension size on its dielectric and electrostrictive properties is expected to deepen the understanding of the microscopic mechanisms of the dielectric and electrostrictive response of relaxor ferroelectrics, and provide a certain experimental basis for the design of materials. . 1 Experimental methods Potassium doping influences PMN-based ceramic ordered microdomains and dielectric and electrostrictive properties. Regions and guess-charges in the matrix do not inhibit the presence of ordered microdomains! The negative charge in the zone and the positive charge in the outer layer of the zone are balanced. The bookmark2 1 peak corresponds to the Nb-O"Nb bond; 1 peak corresponds to the Mg-OMg bond. As can be seen, whether it is the standard sample PMNK0 or the potassium-doped 2% sample PMNK2, the corresponding scattering peak around wave number 792 cm-1 corresponds. The intensity of the Nb-OMg bond is much greater than the intensity of the Nb-pNb bond corresponding to a broad peak at wavenumbers of 560 cm-1, that is, the number of Nb-O"Mg bonds is much greater than the number of Nb-O"Nb bonds. The number of, which further proves that non-stoichiometric 1:1 ordered microdomains do exist in PMN-based ceramics. It was found that the Raman scattering spectrum of PMNK0 without potassium doped standard samples corresponds to Nb~ The ratio of the relative intensity of the 1 broad peak of the OMg bond is 246, and the relative intensity ratio of the corresponding peak of the PMNK2 sample of the potassium doping 2% is 2.43, therefore, the doping of potassium makes the 1:1 ordered domain size in the PMN-based ceramic. It has been reported that the size of the ordered microdomains of PMN-based ceramics is drastically expanded by doping with antimony, and the size of ordered microdomains is reduced by sodium doping, and the potassium doping experiments performed in PMN-based ceramics are consistent with the reported results. The addition of potassium slightly reduces the size of the PMN-based ceramic ordered domains. For simplicity, the shape of the ordered microdomains is a cube with a side length of L, surrounded by a positively charged (PbNbO+ layer) at the periphery of the negatively charged ordered microdomain, if the incorporated potassium ion concentration is x%, When orderly, the ordered microdomain size after potassium doping is: 0.02, substituting into formula (2). If the perovskite lattice constant is 0.4nm, the size of the orderly domain can be 4.6nm. The size of the ordered microdomains of the doped PMN-based ceramics is approximately 4.8nm. Even when the K-doping amount is large, the K-doping decreases the size of the ordered microdomains. The doping of potassium reduces the remaining cerium ions, thus inhibiting the pyrochlore phase. The production of the perovskite phase structure is stabilized, which is completely consistent with the analysis results of the phase composition. In addition, the doping of potassium is acceptor doping. Since the potassium ion substitutes for the lead ion at the A position to generate a negative charge, the potassium ion is not PMN-based ceramics have an even distribution in ordered microdomains and disordered matrices, but they preferentially reside in disordered matrices. That is, the concentration of potassium ions in ordered microdomains is much lower than that in disordered matrices. When the concentration of potassium in the medium is considered to be inhomogeneous, it is clear that the formula is used. 2) The size of PMN-based ceramic ordered microdomains with K-doped concept is also calculated to be larger than 4.6nm. That is, the size of the ordered microdomains of the K-doped sample and the standard sample is closer, and the K-doped orderly microdomains are ordered. The decrease in the size of the region is even more pronounced: First, potassium doping causes the size of the ordered microdomains in the PMN-based ceramic to decrease, that is, the size of the “effective ordered microdomain†decreases, and the “effective ordered microdomain†in the dielectric response. The process is dominated. The reduction in the size of the "effectively ordered microdomains" will inevitably lead to an increase in the phase transition dispersion and a decrease in the dielectric constant. Second, potassium ions replace the lead ions in the A position to make the ferroelectric active oxygen octahedron. The polarization coupling between them weakens, which reduces the dielectric constant and increases the phase change dispersion. At the same time, the larger radius of potassium ions squeezes the active space of the B-site ions, causing the ferroelectrically active antimony ions to decrease their displacement. It is also a cause of the decrease of the dielectric properties. Finally, the trace pyrochlore phase caused by potassium doping also partially reduces the dielectric constant and increases the phase change dispersion. It can also be seen that the addition of potassium reduces the dielectric constant. , but the reduction is very significant Limits, for example, the maximum dielectric constant of the standard sample and potassium doped 1%, 2% and 5% of the sample were 23,079, 22523, 20685, and 17844. The theoretical estimation and Raman spectral results all indicate that potassium doping makes orderly micro The decrease in the size of the area is small. At the same time, potassium ions are not evenly distributed in the ordered microdomains and the disordered matrix, but they preferentially occupy the disordered matrix, ie, the ordered microdomains have a very low concentration of potassium ions, thus the potassium ion in the A position. The separation of ordered microdomains is very limited, so the size of the “effective ordered microdomains†before and after potassium doping is very small, so the dielectric properties only slightly decrease after potassium doping. Finally, the effect of potassium doping on the phase composition of PMN-based ceramics is very limited. The addition of potassium does not substantially change the perovskite phase structure of the ceramic. The content of the second phase, which is detrimental to the dielectric properties, is extremely small in the ceramic. This is one of the reasons why the dielectric properties of the ceramic do not drop much. 4 Potassium doping effect on the electrostriction of PMN-based ceramics The influence of potassium doping on the electrostrictive properties of PMN-based ceramics has been reduced, but the decrease is very limited. The reason why the dielectric constant 2 decreases by C causes this phenomenon is attributed to the following reason that the dielectric constant of the toe decreases. Secondly, the addition of potassium into the bookmark3 to make AM into the bookmark3 slightly reduces the electrostriction of the PMN-based ceramics. This is mainly due to the fact that the doping of potassium reduces the size of the PMN-based ceramic microdomains slightly, and instead of the lead potassium ions, it further makes iron. The coupling strength between the electroactive oxygen octahedrons is reduced, and the electrostriction is reduced. Finally, the larger radius of potassium ions squeezes the active space of the B-site ions, causing the ferroelectrically active antimony ions to decrease in displacement and reduce spontaneous polarization, which is one of the causes of the reduced electrostrictive properties. The extent to which PMN-based ceramics are reduced in electrostriction is very limited. Measurements performed at 20°C under a test condition of 1./m indicate that the electrostriction of undoped standard samples is 0.85. Theoretical calculation and Raman scattering Spectral experiments have shown that the doping of potassium slightly decreases the size of PMN-based ceramics. Potassium doping decreases the dielectric constant of PMN-based ceramics, but the decrease is smaller. The maximum dielectric constants of standard samples and K-doped, 2%, and 5% samples are respectively 23079, 22523, 20685, and 17844. The reason for the reduction of the electrical constant is mainly attributed to the reduction of the size of the "effective ordered microdomains" and the weakening of the polarization coupling between ferroelectrically active oxygen octahedrons by the A-site potassium ions. Potassium doping slightly reduces the electrostriction of PMN-based ceramics. Simple installation, different lamps can be equipped, and the number of lamps can be increased or decreased freely. 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Effect of Potassium Doping on Ordered Micro-zones and Dielectric and Electrostrictive Properties of PMN-based Ceramics