Structure,Doping Mechanism And Optical Properties Of Glass-Ceramics Doped With Transition Metal Ions (Ni/Fe/Co)

Over the past decades,glass-ceramics doped with transition metal ions have become one of the research hotspots of optical functional materials because of their attractive advantages,such as intriguring optical properties,superior mechanical strength,easy and flexible fabrication.So far,many research groups have successfully developed novel glass-ceramics doped with transition metal ions that can be potentially used in tunable lasers,saturable absorbers,noninvasive optical temperature sensors and phosphors for solid-state lighting,etc.However,most studies on this popular topic have focused on the optical properties of the materials without systematically investigating the doping mechanism.Moreover,the practical application of glass-ceramics doped with transition metal ions has not yet made great progress.The spectral characteristics of glass-ceramics doped with transition metal ions are mainly determined by the type,valence state and coordination environment of the doped ions.Therefore,it is of great significance to study the doping mechanism and optical properties of glass-ceramics doped with transition metal ions.The thesis is organized in the following way.The important conclusions and innovative results are summarized as follows.Ni²⁺-doped Zn Si O₃ glass-ceramic has been prepared,and its structure and optical properties has been studied.According to the structural characterization results,it can be found that Ni²⁺ions could change the crystallization behavior of the glass by inducing the precipitation of Zn Si O₃,and then be incorporated into Zn Si O₃ crystalline phases.A possible mechanism of transition metal ion selective doping is proposed:transition metal ions can be used as nucleating agents to induce the precipitation of crystalline phase and then be doped into it.The investigations on the optical properties indicate that Ni²⁺-doped Zn Si O₃ glass-ceramic shows infrared luminescence in the wavelength rage of 1200?2200 nm with the central wavelength of about 1550 nm,which is originated from the ³T₂(³F)?³A₂(³F)transition of octahedal Ni²⁺ions.In addition,the relation between the optical properties of glass-ceramics and fabrication conditions,including the doping concentration and heat treatment temperature,has been invesitigated.Fe²⁺/Fe³⁺-doped?-Ga₂O₃ glass-ceramic has been fabricated and its structure and optical properties were investigated.The glass-ceramic exhibits absorption bands at 1062 nm and1500?2600 nm waveband region,which can be attributed to the ⁵T₂?⁵E transition of octahedral Fe²⁺and ⁵E?⁵T₂transition of tetrahedral Fe²⁺,respectively.Under the excitation of 360 nm,the glass-ceramic shows intense red emission which is originated from the ⁴T₁(⁴G)?⁶A₁(⁶S)transition of octahedral Fe³⁺.The results indicate that Fe²⁺ion can simultaneously substitute for Ga³⁺in the tetrahedral and octahedral sites,while Fe³⁺ion may only incorporate into octahedral sites in?-Ga₂O₃ crystalline phase.Furthermore,by using the Fe²⁺/Fe³⁺-doped?-Ga₂O₃ glass-ceramic,the Q-switched function at 2?m of Tm:YAP laser has been realized.The results demonstrate that Fe²⁺/Fe³⁺-doped?-Ga₂O₃ glass-ceramic would be a promising passive Q-switch for 2?m pulse laser generation and applications.Notably,to the best of our knowledge,this is the first time to report that transparent Fe-doped glass-ceramic can be used as the saturable absorber to produce Q-switched laser in the Tm:YAP laser cavity.The selective doping of Co²⁺ion has been realized in Co²⁺-doped Ga₂O₃,KZn F₃ and Mg F₂glass-ceramics,and thier optical properties have been studied.The absorption spectroscopy and XAFS results demonstrate the selective incorporation of Co dopant in Ga₂O₃ and KZn F₃crystalline phases and formation of the[Co O₄]^6-tetrahedron and[Co F₆]^4-octahedron geometry in the designed glass-ceramics.The stabilization energy of Co²⁺dopant in regular(Ga₂O₃)_x,(Mg F₂)_x and(KZn F₃)_x clusters were calculated by using the first principles theory and methods.The result demonstrates that the selective doping of transition metal ions in glass-ceramics is related to the defect formation energy of the crystalline phase.Combining the experimental and theoretical calculation results,the possible doping mechanism of transition metal ions is proposed:the stabilization trend based on the minimum energy is the driving force for the selective doping of transition metal ions.The results may potentially provide useful reference for the present hot issue of doping in nanocrystals.The optical properties of Co²⁺-doped glass-ceramics containing Ga₂O₃ and KZn F₃ nanocrystals have been also investigated.It has been found that the glass-ceramic embedded Co²⁺:KZn F₃ nanocrystals shows intense broadband luminescence covering the wavelength region from 1400 to 2800 nm due to ⁴T₂(⁴F)?⁴T₁(⁴F)transition.To the best of our knowledge,it is the first time to report the near-/mid-infrared luminescence in Co²⁺-doped glass-ceramics.Another interesting point observed in our experiment is that the stable passive Q-switching function of the Nd:YVO₄ was realized by using glass-ceramic embedded Co²⁺:Ga₂O₃ nanocrystals as a saturable absorber.The pulse width is 280 ns and the corresponding repetition rate is 200 k H,demonstrating its great potential for passive Q-switching.Transition metal ions(Co/Ni/Fe)doped?-(Ga_2-xAl_x)O₃ solid solution glass-ceramics have been designed and successfully fabricated.The structural characterization results show that Ga₂O₃and Al₂O₃ are mutually soluble over the wide Al₂O₃/Ga₂O₃ ratio range(0?2.0)and the composition-tunable?-(Ga_2-xAl_x)O₃ solid solution nanocrystals can be precipitated in silicate glass matrix.When the Al₂O₃/Ga₂O₃ ratio increases from 0 to 2.0,the absorption and luminescence peaks of transition metal ions(Co/Ni/Fe)doped glass-ceramics shift to the shorter wavelengths.Combining with the results of first-principles calculations,the physical mechanism of spectral regulation has been proposed.The solid solution strategy enables to tune the structure of the crystallization phase,resulting in changes of the coordination geometry of doped ions.As a consequence,the tunable absorption and luminescence of the glass-ceramic can be achieved.The results demonstrate that solid solutions forming and doping is an effective approach to tune the optical properties of glass-ceramics doped with transition metal ions.