【摘要】：隨著人們對(duì)環(huán)境保護(hù)的重視,無(wú)鉛壓電陶瓷作為壓電陶瓷中的“后起之秀”,正在逐漸得到研究人員的重視。對(duì)于無(wú)鉛壓電陶瓷的深入研究,使得無(wú)鉛壓電陶瓷有望替代以PZT基陶瓷為主的含鉛壓電陶瓷,這樣不僅會(huì)降低有毒鉛的使用和排放,還可以實(shí)現(xiàn)綠色制造和綠色應(yīng)用,對(duì)于生態(tài)環(huán)境的可持續(xù)發(fā)展產(chǎn)生重要推動(dòng)作用。水熱法屬于一種高效率液相化學(xué)合成法。與傳統(tǒng)的固相法及其他方法相比較,水熱法有很多優(yōu)勢(shì),例如,水熱法獲得的陶瓷納米晶粒徑小、尺寸比較均勻、反應(yīng)溫度低等。因此,水熱法是制備壓電陶瓷納米晶的首選方法。本文采用水熱法,通過(guò)控制礦化劑NaOH的濃度和水熱反應(yīng)時(shí)間,成功制備出了片狀、立方塊狀和線狀等不同形貌的Na0.5Bi0.5TiO3(BNT)納米晶,并描述了不同形貌BNT納米晶的生長(zhǎng)機(jī)理。研究了不同形貌BNT納米晶燒結(jié)成的BNT陶瓷的組織、形貌和電學(xué)性能,并分析了不同燒結(jié)溫度對(duì)BNT壓電陶瓷性能的影響。本文基于納米晶形核及熱力學(xué)分析,利用原位自組裝和溶解再結(jié)晶機(jī)制,描述了不同形貌BNT納米晶的生長(zhǎng)行為和生長(zhǎng)機(jī)理。其主要的生長(zhǎng)行為是:當(dāng)NaOH濃度較低時(shí),c軸方向的生長(zhǎng)速度嚴(yán)重慢于a和b軸。納米晶沿著擇優(yōu)取向方向生長(zhǎng)(a/b軸),從而有利于形成片狀BNT納米晶;隨著NaOH濃度增加,溶解再結(jié)晶機(jī)制會(huì)加速并主導(dǎo)生長(zhǎng)過(guò)程,容易形成立方塊狀BNT納米晶;BNT納米線的的生長(zhǎng)不僅受NaOH濃度的影響,同時(shí)需要一個(gè)較長(zhǎng)的反應(yīng)時(shí)間;得出NaOH的濃度對(duì)于BNT納米晶的形貌起著至關(guān)重要的作用。本文利用不同形貌的BNT納米晶燒制了Na0.5Bi0.5TiO3壓電陶瓷,通過(guò)對(duì)陶瓷組織形貌和電學(xué)性能對(duì)比分析,發(fā)現(xiàn)利用片狀BNT納米晶燒結(jié)的陶瓷相對(duì)最致密,且晶粒較大,組織形貌均一,說(shuō)明BNT納米晶的形貌對(duì)其陶瓷燒結(jié)體的組織有影響,片狀BNT納米晶有助于晶粒的生長(zhǎng)。由片狀BNT納米晶燒制的陶瓷的電學(xué)性能相對(duì)最好,燒成的陶瓷有較高的剩余極化強(qiáng)度和較高的介電系數(shù),其壓電系數(shù)d33可達(dá)87pC/N,這要好于其他文獻(xiàn)中所報(bào)道的BNT體系的壓電性能。通過(guò)研究不同燒結(jié)溫度對(duì)片狀BNT納米晶燒成陶瓷性能的影響,發(fā)現(xiàn)燒結(jié)溫度在1150℃時(shí),陶瓷相對(duì)較為致密,BNT陶瓷的電學(xué)性能相對(duì)最好,從而確定1150℃為最佳燒結(jié)溫度。
[Abstract]:With the importance of environmental protection, lead-free piezoelectric ceramics, as a "rising star" of piezoelectric ceramics, are being paid more and more attention by researchers. With the further study of lead-free piezoelectric ceramics, lead-free piezoelectric ceramics are expected to replace lead-based piezoelectric ceramics, which not only reduce the use and emission of toxic lead, but also achieve green manufacturing and green applications. It plays an important role in promoting the sustainable development of ecological environment. Hydrothermal method belongs to a high efficient liquid phase chemical synthesis method. Compared with traditional solid phase method and other methods, hydrothermal method has many advantages, for example, the size of ceramic nanocrystals obtained by hydrothermal method is small, the size is uniform, and the reaction temperature is low. Therefore, hydrothermal method is the preferred method for the preparation of piezoelectric nanocrystals. In this paper, by controlling the concentration of mineralizer NaOH and hydrothermal reaction time, Na0.5Bi0.5TiO3 (BNT) nanocrystals with different morphologies, such as flake, cubic and linear, were successfully prepared by hydrothermal method. The growth mechanism of BNT nanocrystals with different morphologies was described. The microstructure, morphology and electrical properties of BNT ceramics sintered with different morphologies of BNT nanocrystals were studied, and the effects of sintering temperature on the properties of BNT piezoelectric ceramics were analyzed. Based on the nucleation of nanocrystalline and thermodynamic analysis, the growth behavior and mechanism of BNT nanocrystals with different morphologies were described by in situ self-assembly and dissolution recrystallization. The main growth behavior is that when the concentration of NaOH is low, the growth rate in the direction of C axis is slower than that in axis a and b. The nanocrystals grow along the preferred orientation (a / b axis), thus facilitating the formation of flake BNT nanocrystals. With the increase of NaOH concentration, the mechanism of dissolution and recrystallization accelerates and dominates the growth process. The growth of cubic bulk BNT nanocrystalline nanowires is affected not only by the concentration of NaOH, but also by a long reaction time. It is concluded that the concentration of NaOH plays an important role in the morphology of BNT nanocrystals. In this paper, Na0.5Bi0.5TiO3 piezoelectric ceramics were sintered with BNT nanocrystals with different morphologies. By comparing the microstructure and electrical properties of the ceramics, it was found that the ceramics sintered by BNT nanocrystals were the densest, with larger grains and uniform microstructure. The results show that the morphology of BNT nanocrystals has an effect on the microstructure of the sintered ceramics, and the flake BNT nanocrystals are helpful to the growth of the grains. The ceramic sintered with flake BNT nanocrystals has the best electrical properties. The sintered ceramics have higher residual polarization strength and higher dielectric coefficient. The piezoelectric coefficient d33 can reach 87pC / N, which is better than the piezoelectric properties of BNT system reported in other literatures. The effect of sintering temperature on the properties of BNT nanocrystalline sintered ceramics was studied. It was found that when sintering temperature was 1150 鈩，

本文編號(hào)：2139444