Each row represents cross-sectional SEM images (1st row) & the corresponding schematic illustration images (2nd row) and surface EBSD band contrast maps (3rd row) & the corresponding orientation maps (4th row). d) The comparison graph and table of Lotgering factor for tBT, tBNT and tBNT/BT. Photograph of (b) top view of the samples before printing a top electrode, (c) side view of the samples after printing top and bottom electrodes. d) the optical microscope image of each pattern.
- Piezoelectric materials
- Domain configuration
- Hysteresis loop
- Perovskite structure
- Dielectric properties
- Piezoelectric coefficient and vibration mode
In pyroelectric materials, the charge density also changes depending on the temperature. The strain of the material according to the applied stress and the change of domain configuration at each stage are well illustrated in Figure 1 - 7.
Seed material is required for epitaxial growth of matrix powder on the seed in textured ceramics. Even though the textured ceramic consists of many grains divided by grain boundaries, it shows well-aligned microstructure like that of single crystals.
The other is a non-aqueous system, which is used in academia usually because of the advantages of practical manufacturing processes. The role of the dispersant is to prevent the aggregation of components in slurry to avoid an inhomogeneity of green sheet after tape-casting.
By replacing the A or B zone with different components, the composition of the Aurivillius phase can be easily modified. Through topochemical processes, templates with Aurivillius phase can be transformed into templates with perovskite structure (ABO3).
Research trend of TGG process
However, as shown in Table 2-2, the piezoelectric performance of textured lead-free ceramics is still lower than expected. Therefore, many research groups have tried to improve the piezoelectric properties of textured piezo-ceramics by combining an additional concept such as domain engineering19, core-shell20 with the texturing process. Lv, Densification and texture development of Bi4Ti3O12 templated Na0.5Bi0.5TiO3-BaTiO3 ceramics: Effects of excess Bi2O3, J.
Zhou, Fabrication of Na0.5Bi0.5TiO3-BaTiO3 textured ceramics templated by plate-like Na0.5Bi0.5TiO3 particles, J. Yan, Effect of different templates on structure evolution and large strain response under low electric field in <00l>-textured lead-free BNT-based piezoelectric ceramics, J. Zhai, Effect of different templates and texture on structure evolution and strain behavior of <001>-textured lead-free piezoelectric BNT-based ceramics, J.
Jeon, Synthesis mechanism of Bi0.5Na0.5TiO3 and Bi4.5Na0.5Ti4O15 template during topochemical microcrystal conversion and texturing of Bi0.5(Na0.8K0.2)0.5TiO3 piezoelectric ceramics, J.
Effect of template quality in textured ceramics
- Results and discussion
On the other hand, it is clearly seen that the intensity of the (00l) peaks in Figure 3 - 4 (b), (c) increased compared to the untextured PZT-PZN ceramics. Contrary to expectations considering the microstructure, the poor-quality template-textured PZT-PZN and the good-quality template-textured PZT-PZNN have a similar lotgering factor value. The lottery factor of good-quality template-textured PZT-PZN is on average about 0.03 higher than the lottery factor of poor-quality template-textured PZT-PZN.
The unipolar strain values of the textured PZT-PZN with the worst quality template decreased as shown in Figures 3 - 5. The unipolar strain values of the textured PZT-PZN with the worst template increased slightly compared to the non-textured PZT-PZN ceramics. The textured PZT-PZN ceramic with the worst template shows lower piezoelectric properties than the PZT-PZN ceramic because the remaining templates act as an impurity.
On the other hand, the textured PZT-PZN ceramic has a strain value 1.6 times better than the untextured PZT-PZN ceramic.
Maximizing the effects of texture on piezoelectricity
- Results and discussion
Saito et al., reported about 30% enhanced piezoelectric performance of lead-free textured ceramics with a high value of the degree of orientation, 91%.4 The point is worth noting that only ~30% improvement enables highly textured piezoelectric ceramics without bullets. competitive against piezo-ceramics based on lead zirconate titanate (PZT), a product which has a high market share. For example, according to Sabolsky et al., PMN-0.325PT textured with 0.90 lotgering factor showed 37% and 17% improvement in stress value at 1 kV/mm and d33 and, respectively, while Yan et al.5 reported that 21 % and 9 % improvement of d33 performance and strain at 1 kV/mm respectively, with the same system and the same texture factor scale (90. From now on, PMN.0325PT, tBT, tBNT and tBNT/BT are abbreviation for randomly oriented PMN-0.325PT, BT-templated textured PMN-0.325PT, BNT-templated textured PMN-0.325PT, BNT-templated textured PMN-0.325PT, and BT, respectively, i.e., tBNT/ BT is textured through ceramics - TGG Method.
But the difference in size distribution in untextured grains existed depending on the type of templates for growth of textured grains. Considering that the growth distance and randomization factor of textured ceramics increase proportionally with the sintering time (typically >10 h) at maximum temperature, untextured large grains can also occur, and eventually these grains grow independently as large as the patterned textured grains ( especially in the case of the grains far away from the templates). The interestingness of this phenomenon is that the bimodal size distribution of textured ceramics with BNT template occurs among the matrix grains, except for the large textured grains due to the BNT templates.
This bimodality in tBNT ceramics is so strong that the size of untextured large grains is the same as that of textured grains due to the AGG mechanism.
Electric field concentration
- Results and discussion
As the distance between the patterns decreases, the degree of interference increases, resulting in a weakening of the electric field concentration. On the contrary, the concentration of the electric field was promoted as the distance between the patterns indeed increased. In the case of interval 1 where all samples respond up to the maximum external electric field of 5 kV/mm, the elongation of the samples is equal.
It may appear that the significant interference of the specified inter-pattern distance causes ineffectiveness of electric field concentration effect in patterns 1 and 2. However, the increase of the inter-pattern distance leads to a further improvement of the strain properties by realizing expected electric field concentration in samples. This means that pattern 3 has the best performance among electrode patterns for electric field concentration.
This is due to the fact that a shorter distance between samples results in a smaller electric field concentration effect than an increase in interference between samples.
Piezoelectric ceramics are highly attractive materials due to their ability to convert energy between electrical and mechanical sources. It is important to remember that most of the piezoelectric ceramics studied today are ferroelectric piezoelectric materials, we believe that transparent piezoelectric ceramics will show improved photovoltaic ferroelectric effect even in the bulk state. However, it is difficult to have piezoelectricity and transparency simultaneously in ceramics, because piezoelectricity and permeability are trade-offs.
Therefore, it is rare to report both piezoelectricity and transparency simultaneously, and most reported cases focus on either piezoelectricity or transparency.1-8. One of the most effective ways to make transparent piezoelectric ceramics is hot pressure sintering. Recently, some research has been reported on piezoelectric ceramics using the hot press sintering process, which have transparency and piezoelectricity.9-22 Undoubtedly, the hot press sintering process makes it possible to produce ceramics with densities of high, which helps greatly in improving transmission, but that process is not suitable for mass production and has high costs.
In this work, we fabricated the high-performance piezoelectric ceramic with ultra-high transmittance by co-doping with pressureless sintering.
Results and discussion
The piezoelectric coefficient, d33, also increased with the increase of the value of x, showing a maximum value when x = 3.1. Then d33 decreased with the increase of x and almost lost the piezoelectricity after x = 5.0. The reason for the enhancement of the piezoelectric properties of PLSMNTx ceramics is the enhanced local structural heterogeneity through Sm3+ doping.
Apparently it is because the surface roughness is improved and the diffuse reflection of the surface is decreased. The piezoelectric properties, d33 and strain decreased as the ceramic thickness decreased as shown in Figure 6 - 6 (e). Unlike the piezoelectric characteristics, which decreased with thickness, the sound pressure characteristics did not show a significant change according to the thickness of the piezoelectric element.
The need for a transparent piezoelectric material has arisen with the recent development of the display field.
비록 고마운 분들 모두에게 부족하지만 이 자리를 통해 감사의 마음을 전하고 싶습니다. 먼저, 제가 박사과정을 밟을 수 있도록 지도해주신 조욱 교수님께 감사의 말씀을 전하고 싶습니다. 가르침을 받은 후, 앞으로도 나는 항상 반에서 밑바닥까지 올라가려고 노력할 것입니다.
그리고 석사과정 동안 저를 지도해주신 중앙대학교 고정혁 교수님께도 감사의 말씀을 전하고 싶습니다. 압전 분야에 대한 지식과 다양한 과제 경험, 교수님께서 가르쳐주신 인생 수업은 제가 회사 생활과 박사 과정을 공부하는 데 큰 도움이 되었습니다. 그리고 함께 일했던 AEDM 연구실 선후배들에게도 감사 인사를 전하고 싶습니다.
(주)모디노칩 관계자분들께도 감사의 말씀을 전하고 싶습니다. 기업 연구와 비즈니스 연계 측면에 대해 가르쳐주셔서 감사합니다.