Proučavanje luminescencije uzbudom naviše u nanokristalima BaTiO3: Ho3+

Visible up-conversion emissions at 435, 545, 580, 675 and 690 nm and 437, 547, 575 and 675 nm have been obtained from BaTiO3 doped with 4 % Ho3+ ions in two different forms of the prepared samples, powder and thin film, under 808 nm laser diode excitation emissions. Combined with the energy level structure of Ho3+ ions and the kinetics of the visible emissions, the up-conversion mechanism has been analyzed and explained. The blue, green and red emissions of both samples have been attributed to the ground state-directed transition from 5F1, 5S2 and 5F5 states, respectively, which are populated through excited state absorption on 808 nm excitation. Nano-structure pure barium titanate and doped with different concentrations of Ho3+ ions in the form of powder and thin films have been prepared by so-gel technique, using barium acetate (Ba(CH3CHOO)2) and titanium isopropoxide (Ti((CH3)2CHO)4) as precursors. The thin films were prepared by spin-coating sol-gel method. The as-grown thin film and powders were found to be amorphous, which crystallized to the tetragonal phase after synthesization at 750 °C in air for 30 minutes. The crystallite size of thin film and powder samples both doped with 4 % Ho3+ ions, were found to be equal to 11 and 16 nm, respectively.Uzbudom laserskom diodom na 808 nm postigli smo emisije u vidljivom području na 435, 545, 580, 675 i 690 nm, te na 437, 547, 575 and 675 nm, u BaTiO3 punjenom s 4 % Ho3+ iona u uzorcima dvaju oblika, prahu i tankom sloju. Uzimajući u obzir stanja iona Ho3+ i kinetiku emisije fotona, analizirali smo i objasnili mehanizam uzbude naviše. Emisije oba uzorka u plavom, zelenom i crvenom području pripisuju se prijelazima u osnovno stanje sa stanja 5F1, 5S2 odn. 5F5 koja se pune apsorpcijom fotona 808 nm u višim stanjima Ho3+ iona. Metodom sol-gel pripremili smo nanostrukturni čist barijum titanat i barijum titanat punjen s dvjema koncentracijama Ho3+ iona, kao prah i kao tanke slojeve. Rabili smo barijum acetat (Ba(CH3CHOO)2) i titanijev izopropoksid (Ti((CH3)2CHO)4) za njihovu pripremu. Tanke smo slojeve dobivali centrifugiranjem sol-gela. Svježe pripremljeni tanki slojevi i prah su amorfni, ali se kristaliziraju zagrijavanjem na 750 ◦C u zraku tijekom 30 minuta. Veličina kristalita u tankom sloju i prahu, svaki punjen s 4 % Ho3+ iona, iznosi 11 odn. 16 nm

Proučavanje luminescencije uzbudom naviše u nanokristalima BaTiO3: Ho3+

Visible up-conversion emissions at 435, 545, 580, 675 and 690 nm and 437, 547, 575 and 675 nm have been obtained from BaTiO3 doped with 4 % Ho3+ ions in two different forms of the prepared samples, powder and thin film, under 808 nm laser diode excitation emissions. Combined with the energy level structure of Ho3+ ions and the kinetics of the visible emissions, the up-conversion mechanism has been analyzed and explained. The blue, green and red emissions of both samples have been attributed to the ground state-directed transition from 5F1, 5S2 and 5F5 states, respectively, which are populated through excited state absorption on 808 nm excitation. Nano-structure pure barium titanate and doped with different concentrations of Ho3+ ions in the form of powder and thin films have been prepared by so-gel technique, using barium acetate (Ba(CH3CHOO)2) and titanium isopropoxide (Ti((CH3)2CHO)4) as precursors. The thin films were prepared by spin-coating sol-gel method. The as-grown thin film and powders were found to be amorphous, which crystallized to the tetragonal phase after synthesization at 750 °C in air for 30 minutes. The crystallite size of thin film and powder samples both doped with 4 % Ho3+ ions, were found to be equal to 11 and 16 nm, respectively.Uzbudom laserskom diodom na 808 nm postigli smo emisije u vidljivom području na 435, 545, 580, 675 i 690 nm, te na 437, 547, 575 and 675 nm, u BaTiO3 punjenom s 4 % Ho3+ iona u uzorcima dvaju oblika, prahu i tankom sloju. Uzimajući u obzir stanja iona Ho3+ i kinetiku emisije fotona, analizirali smo i objasnili mehanizam uzbude naviše. Emisije oba uzorka u plavom, zelenom i crvenom području pripisuju se prijelazima u osnovno stanje sa stanja 5F1, 5S2 odn. 5F5 koja se pune apsorpcijom fotona 808 nm u višim stanjima Ho3+ iona. Metodom sol-gel pripremili smo nanostrukturni čist barijum titanat i barijum titanat punjen s dvjema koncentracijama Ho3+ iona, kao prah i kao tanke slojeve. Rabili smo barijum acetat (Ba(CH3CHOO)2) i titanijev izopropoksid (Ti((CH3)2CHO)4) za njihovu pripremu. Tanke smo slojeve dobivali centrifugiranjem sol-gela. Svježe pripremljeni tanki slojevi i prah su amorfni, ali se kristaliziraju zagrijavanjem na 750 ◦C u zraku tijekom 30 minuta. Veličina kristalita u tankom sloju i prahu, svaki punjen s 4 % Ho3+ iona, iznosi 11 odn. 16 nm

Strukturna i dielektrična svojstva nanostrukturnih prahova BaTiO3 punjenih ionima Eu3+ I pripremljenih sol-gel procesom

Nano-structure BaTiO3 powders doped with Eu3+ ions have been prepared by a sol-gel technique. X-ray diffraction (XRD) results indicate that BaTiO3 gel powders crystallize into tetragonal symmetry on heat treatment at 750 ◦C. Particle sizes as small as 3.5 nm were measured for pure BaTiO3 powders. The XRD data were confirmed by transmission electron microscope. Room-temperature luminescence spectra of BaTiO3:0.5% Eu3+, BaTiO3:1% Eu3+ and BaTiO3:2% Eu3+ powders have been measured. The luminescence spectra of prepared ultrafine powders are dominated by the 5D0 →7F2 transition in Eu3+, suggesting a strong distortion of the Eu3+ sites. The foreign ions are mainly accommodated in Ba2+ tetragonal sites, which are then distorted by the occurrence of different ionic charge of the two cations Ba2+ and Eu3+. The dielectric constant, ε, of BaTiO3, BaTiO3:0.5% Eu3+, BaTiO3:1% Eu3+ and BaTiO3:2% Eu3+ powders at frequency 100 Hz was found to be equal to 1000, 1211, 1455 and 1800, respectively. This high dielectric constant is believed to arise from the increase of the crystallite size, when increasing the concentration of Eu3+ ions. After annealing in argon at 400 ◦C for two hours, at 100 Hz, the dielectric constant of the pure sample was 625 and the AC resistivity also decreased. The room temperature (RT) AC resistivity of the samples depends on the concentration of Eu3+ ions in BaTiO3 powders, and was found to decrease as the concentration of Eu3+ ions increased.Pripremali smo sol-gel metodom nanostrukturne prahove BaTiO3 punjene Eu3+ ionima. Difrakcija X-zračenja (DXZ) pokazuje da se gel prahovi BaTiO3 kristaliziraju u tetragonalnoj simetriji zagrijavanjem na 750 ◦C. Utvrdili smo veličine zrna od samo 3.5 nm u čistom prahu BaTiO3. Podatke od DXZ potvrdili smo prolaznom elektronskom mikroskopijom. Mjerili smo fotoluminescentne spektre prahova BaTiO3:0.5% Eu3+, BaTiO3:1% Eu3+ i BaTiO3:2% Eu3+ na sobnoj temperaturi. U luminescentnim spektrima pripremljenih ultrafinih prahova prevladava prijelaz 5D0 →7F2 u Eu3+, što ukazuje na snažna izobličenja na mjestima Eu3+ iona. Ugrađeni se ioni Eu3+ uglavnom smještaju na tetragonalne položaje Ba2+, a velika razlika ionskih naboja dvaju kationa, Ba2+ i Eu3+, uzrokuje snažne promjene oko tog defekta. Dielektrične konstante, ε, prahova BaTiO3, BaTiO3:0.5% Eu3+, BaTiO3:1% Eu3+ i BaTiO3:2% Eu3+ na frekvenciji 100 Hz prema našim mjerenjima iznose 1000, 1211, 1455 odn. 1800. Smatramo da su tako velike vrijednosti dielektrične konstante posljedica povećanih veličina kristalita za veća punjenja ionima Eu3+. Nakon opuštanja u argonu na 400 ◦C tijekom dva sata, dielektrična konstanta čistog praha bila je 625, a otpornost se također smanjila. Izmjenična otpornost prahova BaTiO3 ovisi o punjenju ionima Eu3+ i nalazi se da se smanjuje kada se poveća sadržaj iona Eu3+

Strukturna i dielektrična svojstva nanostrukturnih prahova BaTiO3 punjenih ionima Eu3+ I pripremljenih sol-gel procesom

Nano-structure BaTiO3 powders doped with Eu3+ ions have been prepared by a sol-gel technique. X-ray diffraction (XRD) results indicate that BaTiO3 gel powders crystallize into tetragonal symmetry on heat treatment at 750 ◦C. Particle sizes as small as 3.5 nm were measured for pure BaTiO3 powders. The XRD data were confirmed by transmission electron microscope. Room-temperature luminescence spectra of BaTiO3:0.5% Eu3+, BaTiO3:1% Eu3+ and BaTiO3:2% Eu3+ powders have been measured. The luminescence spectra of prepared ultrafine powders are dominated by the 5D0 →7F2 transition in Eu3+, suggesting a strong distortion of the Eu3+ sites. The foreign ions are mainly accommodated in Ba2+ tetragonal sites, which are then distorted by the occurrence of different ionic charge of the two cations Ba2+ and Eu3+. The dielectric constant, ε, of BaTiO3, BaTiO3:0.5% Eu3+, BaTiO3:1% Eu3+ and BaTiO3:2% Eu3+ powders at frequency 100 Hz was found to be equal to 1000, 1211, 1455 and 1800, respectively. This high dielectric constant is believed to arise from the increase of the crystallite size, when increasing the concentration of Eu3+ ions. After annealing in argon at 400 ◦C for two hours, at 100 Hz, the dielectric constant of the pure sample was 625 and the AC resistivity also decreased. The room temperature (RT) AC resistivity of the samples depends on the concentration of Eu3+ ions in BaTiO3 powders, and was found to decrease as the concentration of Eu3+ ions increased.Pripremali smo sol-gel metodom nanostrukturne prahove BaTiO3 punjene Eu3+ ionima. Difrakcija X-zračenja (DXZ) pokazuje da se gel prahovi BaTiO3 kristaliziraju u tetragonalnoj simetriji zagrijavanjem na 750 ◦C. Utvrdili smo veličine zrna od samo 3.5 nm u čistom prahu BaTiO3. Podatke od DXZ potvrdili smo prolaznom elektronskom mikroskopijom. Mjerili smo fotoluminescentne spektre prahova BaTiO3:0.5% Eu3+, BaTiO3:1% Eu3+ i BaTiO3:2% Eu3+ na sobnoj temperaturi. U luminescentnim spektrima pripremljenih ultrafinih prahova prevladava prijelaz 5D0 →7F2 u Eu3+, što ukazuje na snažna izobličenja na mjestima Eu3+ iona. Ugrađeni se ioni Eu3+ uglavnom smještaju na tetragonalne položaje Ba2+, a velika razlika ionskih naboja dvaju kationa, Ba2+ i Eu3+, uzrokuje snažne promjene oko tog defekta. Dielektrične konstante, ε, prahova BaTiO3, BaTiO3:0.5% Eu3+, BaTiO3:1% Eu3+ i BaTiO3:2% Eu3+ na frekvenciji 100 Hz prema našim mjerenjima iznose 1000, 1211, 1455 odn. 1800. Smatramo da su tako velike vrijednosti dielektrične konstante posljedica povećanih veličina kristalita za veća punjenja ionima Eu3+. Nakon opuštanja u argonu na 400 ◦C tijekom dva sata, dielektrična konstanta čistog praha bila je 625, a otpornost se također smanjila. Izmjenična otpornost prahova BaTiO3 ovisi o punjenju ionima Eu3+ i nalazi se da se smanjuje kada se poveća sadržaj iona Eu3+

Sol–gel-derived photonic structures handling erbium ions luminescence

The sol–gel technique is a very flexible, relatively simple, and low-cost method to fabricate many different innovative photonic structures characterized by specific functionalities. During synthesis, starting from the molecular level, compounds or composites with well controlled composition can be obtained as thin films, powders or monoliths. These materials can be used to prepare such structures as waveguides, photonic crystals, coatings, and bulk glasses including spheres, rings and other geometries exploited in optical resonators fabrication. This article presents some results obtained by the authors in the field of the sol–gel-derived photonic structures. To emphasise the scientific and technological interest in this kind of systems and the versatility of the sol–gel route, the glass-based nano and micrometer scale range systems are discussed. Particularly, the following systems are described: silica–hafnia glass and glass–ceramic planar waveguides, nanosized tetraphosphates, and silica colloidal crystals. The attention is focused on the spectroscopic properties of Er3+-activated materials that due to the light emission can be used in the integrated optics area covering application in sensing, biomedical diagnostic, energy conversion, telecommunication, lighting, and photon management

Up-conversion luminescence application in Er³⁺: TiO₂ thin film prepared by dip coating sol-gel route

706-711Sol-gel derived nano-crystalline titanium dioxide films doped with 1 up to 5% Er³⁺ ions were prepared by dip coating sol-gel method. The coating sol was obtained by hydrolysis of Ti(OC₄H₉)₄ in ethanol/HCl solution. The FT-Raman and the X-ray diffraction (XRD) were carried out to determine the crystal structure of the prepared samples. The morphology SEM and the cross – sectional of the film were used to characterize the microstructure and the thickness of the prepared film. It is shown that relative homogeneous, crack-free and transparent film was achieved via dipping process at 500ºC.After the excitation with laser diode at wavelength 808 nm, visible (Vis) and infrared (IR) up-conversion emissions were evidenced in the thin film samples under investigation. The up-conversion was found to depend strongly on the Er³⁺ ion concentrations. The visible emission was found to be at 540, 560, 590 and 640 nm for thin film. They are attributed to intra-4f transition of Er³⁺ ions and assigned to the (²H₁₁/₂ + ⁴S₃/₂) and ⁴F₉/₂, which are populated through excited state absorption (ESA) for 808 nm excitation

Thermal Effect of Er³⁺ Ions Embedded in Smart Nano-Composite Oxide Material Prepared by Sol-Gel Technique

The phosphosilicate for planar waveguides fabrication by using sol-gel, and particularly erbium-doped waveguide amplifiers, is reviewed. In particular, efforts to use sol-gel to improve molecular homogeneity in Er-doped phosphosilicate-based monolith and thin films will be discussed. A variety of material studies was carried out to investigate and optimize the sample preparation condition for such application. These include X-ray diffraction, the Fourier transform infrared and optical transmittance, absorption and refractive index calculation. The erbium nitrate precursors use is shown to alter the Er³⁺ ions doping in the prepared samples thermally treated in the final monolith glass form, in comparison to the use of thin film phosphosilicate sol-gel sample. Excess heat treatment is used to force prepared samples crystallization, moreover resulting photoluminescence analysis is used to detect the co-operative-up-conversion sample properties before and after heating

Thermal Effect of Er 3+

The phosphosilicate for planar waveguides fabrication by using sol-gel, and particularly erbium-doped waveguide amplifiers, is reviewed. In particular, efforts to use sol-gel to improve molecular homogeneity in Er-doped phosphosilicate-based monolith and thin films will be discussed. A variety of material studies was carried out to investigate and optimize the sample preparation condition for such application. These include X-ray diffraction, the Fourier transform infrared and optical transmittance, absorption and refractive index calculation. The erbium nitrate precursors use is shown to alter the Er³⁺ ions doping in the prepared samples thermally treated in the final monolith glass form, in comparison to the use of thin film phosphosilicate sol-gel sample. Excess heat treatment is used to force prepared samples crystallization, moreover resulting photoluminescence analysis is used to detect the co-operative-up-conversion sample properties before and after heating