發(fā)布時(shí)間：2018-06-03 18:29

  本文選題：高溫 + 高壓��； 參考：《中國科學(xué)技術(shù)大學(xué)》2017年博士論文

【摘要】：溫度、壓力作為決定物質(zhì)狀態(tài)的兩個(gè)重要物理參量,在改變物質(zhì)結(jié)構(gòu),引起相變等方面起著重要作用。壓力可以縮短原子間的距離,調(diào)整晶體結(jié)構(gòu)和電子軌道,而溫度則可以幫助表面活性能來克服不同的結(jié)構(gòu)之間的勢(shì)壘。物質(zhì)的各種物理化學(xué)性質(zhì)依賴于物質(zhì)的結(jié)構(gòu)、尺寸和形貌等。因此,包括低溫、高溫、高壓在內(nèi)的極端條件可以改變物質(zhì)的存在狀態(tài),獲得在常溫常壓下所隱藏的新奇現(xiàn)象。本文主要制備了各種不同大小和形貌的發(fā)光材料,研究溫度壓力等對(duì)材料結(jié)構(gòu)、形貌、尺寸的改變,探究樣品在極端條件下物理化學(xué)特性,為優(yōu)異新材料的探索提供線索。全文共有六章,內(nèi)容如下:第一章、對(duì)高壓技術(shù)和實(shí)驗(yàn)方法,高壓領(lǐng)域的部分進(jìn)展及發(fā)光材料做了簡(jiǎn)要介紹。第二章、用水熱法合成了六方相NaYF_4:Yb,Ln微米晶。首先對(duì)NaYF_4:Yb,Ho微米晶在高溫下的上轉(zhuǎn)換和下轉(zhuǎn)換發(fā)光強(qiáng)度分別進(jìn)行了研究。在加熱至500℃并降溫的過程中,兩種不同類型的發(fā)光強(qiáng)度一直在增加。降至室溫后,上轉(zhuǎn)換和下轉(zhuǎn)換發(fā)光強(qiáng)度分別是未加熱前的數(shù)百和幾十倍。結(jié)合XRD,紅外吸收光譜,吸收光譜以及電子自旋共振光譜,我們認(rèn)為加熱處理去除了樣品表面和內(nèi)部殘留的有機(jī)基團(tuán)使上轉(zhuǎn)換發(fā)光增強(qiáng),而生成的C=C等不飽和鍵使下轉(zhuǎn)換發(fā)光增強(qiáng)。同時(shí)我們研究了在不同溫度和高壓下稀土摻雜NaYF_4的上轉(zhuǎn)換光譜。Er的熱耦合能級(jí)2~H_(11/2)和4~S_(3/2)的比值隨溫度增加而減小,其規(guī)律可用來測(cè)量100-700 K之間的溫度。該熱耦合能級(jí)發(fā)光強(qiáng)度之比在高壓下也發(fā)生單調(diào)變化,亦可用以測(cè)量壓力的變化。第三章、結(jié)合水熱和高溫退火的方法合成了 YV0_4:Yb,Er熒光粉,并對(duì)各項(xiàng)條件進(jìn)行了優(yōu)化處理,該熒光粉可以同時(shí)實(shí)現(xiàn)下轉(zhuǎn)換和上轉(zhuǎn)換兩種發(fā)光�？蓪⑵鋺�(yīng)用于太陽能電池,同時(shí)實(shí)現(xiàn)紫外和紅外到可見的光能轉(zhuǎn)化。隨后又合成了一系列Tm_3+,Er_3+,Ho_3+和Yb_3+摻雜YVO4的上轉(zhuǎn)換熒光粉,它們分別發(fā)射的藍(lán)光,綠光和黃光。嘗試著用合成的上轉(zhuǎn)換熒光粉分別組裝了可以藍(lán)光、綠光和紅光的上轉(zhuǎn)換LED。通過調(diào)整Ho_3+、Tm_3+的摻雜比例,實(shí)現(xiàn)了上轉(zhuǎn)換白光,其在CIE坐標(biāo)中接近標(biāo)準(zhǔn)白光。從變溫上轉(zhuǎn)換光譜看,將YV0_4:Yb,Tm,Ho用作白光LED時(shí),應(yīng)考慮其熒光的溫度效應(yīng)。第四章、用水相反應(yīng)法分別合成了純的正交相和六方相的EuF_3納米晶。高壓熒光光譜表明,正交相EuF_3轉(zhuǎn)變?yōu)榱较嗟膲毫c(diǎn)比塊材高約1.5 GPa。與在靜水壓下的一直穩(wěn)定存在不同,六方相EuF_3會(huì)在非靜水壓下經(jīng)歷從六方到正交然后再回到六方的循環(huán)相變。其從六方到正交的相變壓力很小(0.07 GPa),3～10 GPa又從正交相變回六方相。同樣的,六方相EuF_3在高溫下也會(huì)經(jīng)歷從六方到正交然后再回到六方的循環(huán)相變。第五章、用水熱和溶劑熱法合成了立方Sb_20_3微米晶和正交Sb_20_3納米帶。采用原位高壓拉曼的方法研究了立方Sb2O3微米晶在常溫的結(jié)構(gòu)穩(wěn)定性。在高于25 GPa的壓力下,Sb_20_3轉(zhuǎn)變?yōu)楦呙芏鹊姆蔷?激光輻照可以促進(jìn)該過程。數(shù)分鐘的輻照可以將完全相變所需的壓力從大于35 GPa降至27 GPa。完全卸壓后,非晶相可以部分重新變?yōu)榱⒎较?激光輻照同樣可以加速該過程。采用拉曼光譜和同步輻射XRD的方法對(duì)其在高壓下的相變進(jìn)行了研究,高壓拉曼和高壓XRD結(jié)果都表明,正交相Sb_20_3納米帶在13 GPa轉(zhuǎn)變?yōu)橐粋�(gè)結(jié)構(gòu)未知的高壓相。第六章對(duì)研究工作做了總結(jié)。
[Abstract]:Temperature, pressure, as the two important physical parameter determining the state of the material, plays an important role in changing the structure of the material and causing the phase transition. The pressure can shorten the distance between the atoms, adjust the crystal structure and the electron orbit, and the temperature can help the surface activity to take the barrier between different structures. The chemical properties depend on the structure, size and morphology of the material. Therefore, the extreme conditions, including low temperature, high temperature and high pressure, can change the state of the material and obtain the novelty hidden under the normal temperature and atmospheric pressure. In this paper, various luminescent materials of different sizes and morphologies have been prepared, and the structure and structure of temperature and pressure on the material are studied. The physical and chemical properties of the samples under extreme conditions are explored to provide clues to the exploration of excellent new materials. There are six chapters in the full text as follows: in Chapter 1, a brief introduction to high pressure technology and experimental methods, some progress in the field of high pressure and luminescent materials is briefly introduced. The second chapter, the synthesis of six square phase NaYF_4:Yb, Ln micro At first, the upconversion and down conversion luminescence intensities of NaYF_4:Yb, Ho microcrystals at high temperature were studied. During heating to 500 C and cooling, the two different types of luminescence intensities have been increasing. After reducing to room temperature, the upconversion and down conversion luminescence intensities are hundreds and dozens times as many times as before unheated. Combined with XRD, In the infrared absorption spectrum, absorption spectrum and electron spin resonance spectrum, we think that the upconversion luminescence is enhanced by the removal of the residual organic groups in the surface and inside of the sample, while the generated C=C and other unsaturated bonds enhance the down conversion luminescence. At the same time, we studied the upconversion light of the rare earth doped NaYF_4 at different temperatures and high pressures. The ratio of the thermal coupling energy level 2~H_ (11/2) and 4~S_ (3/2) of the spectrum.Er decreases with the increase of temperature. The law can be used to measure the temperature between 100-700 K. The ratio of the luminescence intensity of the thermal coupling energy level also varies monotonically at high pressure, and can also be used to measure the change of pressure. The third chapter, combined with the methods of water heat and high temperature annealing, syntheses YV0_4:Yb, E The R phosphor is optimized and the conditions are optimized. The phosphor can simultaneously realize down conversion and upconversion two kinds of luminescence. The phosphor can be used in solar cells, and the ultraviolet and infrared to visible light energy conversion can be realized. Then a series of Tm_3+, Er_3+, Ho_3+ and Yb_3+ doped YVO4 up-converted phosphors are synthesized. The blue light, green light and yellow light are launched. The upconversion LED., which can be blue, green and red, is assembled by using the synthetic upconversion phosphor. The up conversion white light is realized by adjusting the proportion of Ho_3+ and Tm_3+, which is close to the standard white light in the CIE coordinates. From the variable temperature conversion spectrum, the YV0_4:Yb, Tm and Ho are used as white LED. The temperature effect of its fluorescence is considered. In the fourth chapter, the pure orthogonal and six square phase EuF_3 nanocrystals are synthesized by the aqueous phase reaction method. The high pressure fluorescence spectra show that the pressure point of the orthogonal phase EuF_3 transformation to six square phase is about 1.5 GPa. higher than that of the block material, and the six square phase EuF_3 will experience under the non hydrostatic pressure. The cyclic phase transition from the six party to the orthogonal and then back to the six party. The phase transition pressure from the six to the orthogonal (0.07 GPa) and the 3~10 GPa from the orthogonal phase transition back to the six square phase. The same, the six square phase EuF_3 will also undergo the cyclic phase transition from six to the orthogonal and then back to the six party. The structure stability of cubic Sb2O3 micron crystal at normal temperature is studied by in situ high pressure Raman spectroscopy. Under the pressure of higher than 25 GPa, Sb_20_3 is transformed into a high density amorphous phase. The laser irradiation can promote the process. A few minutes of irradiance can increase the pressure required for the complete phase transition from more than 3. After the 5 GPa is reduced to 27 GPa. completely, the amorphous phase can be partially converted into cubic phase, and the laser irradiation can also accelerate the process. The phase transition under high pressure is studied by Raman and synchrotron radiation XRD. The results of High Pressure Raman and high pressure XRD show that the orthogonal Sb_20_3 nanoribbons are converted to a node in 13 GPa. The sixth chapter summarizes the research work.
【學(xué)位授予單位】：中國科學(xué)技術(shù)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：O482.31

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