The Structure And Luminescence Propetry Of Rare-earth Materials Series: Nalnf₄（ln=y, Ho, Tb） Under High

As typical host materials of rare earth semiconductor luminescence materials, the seriesmaterial of NaLnF₄is the one of most important materials in the electronics industry. It iswidely used in many fields, such as solid-state laser, infrared detection, solar battery, etc.However, the research of those kind materials is just beginning. So far, there are only twopapers about the structure and properties research of bulk materials NaYF₄. Therefore, it isimportant to discover the structure and properties of those kind materials under high pressure.In this paper, we study the crystal structure and luminescence property of NaLnF₄（Ln=Y,Ho, Tb）. Those series materials were synthetized by ethanol solvent method. The structures ofsamples are all hexagonal structure, and the morphology of samples is all nanorods. Thediameters of nanorods are100nm,50nm,25nm, respectively.We study the structure of NaLnF₄（Ln=Y, Ho, Tb） through in situ high-pressure X-raydiffraction spectroscopy technology. In situ high-pressure X-ray diffraction spectroscopy havebeen performed on NaLnF₄（Ln=Y, Ho, Tb） and the pressure reached31.82GPa,30.47GPa,25.99GPa, respectively. We find that there kinds of materials perform phase transition formhexagonal phase to face-centered cubic phase. This is different from former reports aboutNaYF₄bulk materials performing no phase transition up to22GPa. Moreover, there is noreport about NaHoF₄and NaTbF₄under high pressure and we report the performance ofNaHoF₄and NaTbF₄under high pressure. Moreover, we also find a rule: the structuretransition pressures of those three materials are different, the less diameter of ionic radius, thephase transition pressure will be lower. We explain this phenomenon: with the diameter ofrare earth ions increasing, the interaction of ions will be weak and the phase transitionpressure will be decrease.Luminescence study of NaHoF₄has performed. We use633nm laser as light sourse,observe a luminous zone center wavelength at645nm. Compared to previous research, wefind this luminous zone due to fluorescence radiation of Ho³⁺ions （⁵F₅→⁵I₈）. And we alsoobserve that the peak place with pressure change coefficient will be different at17.89GPafrom the in situ high-pressure Luminescence spectroscopy of NaHoF₄. We explain this phenomenon: the crystal structure transition will change the Ho³⁺electron energy level; thenresult in the peak place with pressure change coefficient will be different.