Spectroscopic properties of erbium-doped oxyfluoride phospho-tellurite glass and transparent glass-ceramic containing BaF2 nanocrystals

The ErF3-doped oxyfluoride phospho-tellurite glasses in the (40-x) TeO2-10P2O5-45 (BaF2-ZnF2) -5Na2O-xErF3 system (where x = 0.25, 0.50, 0.75, 1.00, and 1.25 mol%) have been prepared by the conventional melt-quenching method. The effect of erbium trifluoride addition on thermal, structure, and spectroscopic properties of oxyfluoride phospho-tellurite precursor glass was studied by differential scanning calorimetry (DSC), Fourier-transform infrared (FTIR), and Raman spectroscopy as well as emission measurements, respectively. The DSC curves were used to investigate characteristic temperatures and thermal stability of the precursor glass doped with varying content of ErF3. FTIR and Raman spectra were introduced to characterize the evolution of structure and phonon energy of the glasses. It was found that the addition of ErF3 up to 1.25 mol% into the chemical composition of phospho-tellurite precursor glass enhanced 2.7 µm emission and upconversion. By controlled heat-treatment process of the host glass doped with the highest content of erbium trifluoride (1.25 mol%), transparent erbium-doped phospho-tellurite glass-ceramic (GC) was obtained. X-ray diffraction analysis confirmed the presence of BaF2 nanocrystals with the average 16 nm diameter in a glass matrix. Moreover, MIR, NIR, and UC emissions of the glass-ceramic were discussed in detail and compared to the spectroscopic properties of the glass doped with 1.25 mol% of ErF3 (the base glass)

Study of visible, NIR, and MIR spectroscopic properties of Er3+-doped tellurite glasses and glass–ceramics

In this paper, the structural, thermal, optical, and spectroscopic properties of Er3+-doped tellurite glasses with the composition 68.25TeO2–19.5ZnO–9.75X–2.5Er2O3 (in mol%) with X = BaO, Na2O, and Bi2O3 are reported. The glasses were prepared using the standard melt quenching method. The investigated glasses exhibit low phonon energy (∼745 cm−1) and low glass transition temperature varying between 300 and 350°C depending on the glass composition. The Raman spectra show a regular tellurite structure with variations in the number of bridging and non-bridging oxygens depending on the glass composition, the Na2O and Bi2O3-containing glasses having the most and the least polymerized network, respectively. A thermal treatment of the glasses leads to the formation of crystals, the composition of which depends on the glass composition, as revealed by X-ray diffraction analysis and confirmed using scanning electron microscope-energy-dispersive spectroscopy. The precipitation of Er-containing crystals in the Na2O and BaO-containing glasses leads to an increase in the intensity of the upconversion emissions. Although the Er3+ ions remain in the amorphous part of the Bi2O3-containing glass after heat treatment, it is the precipitation of Bi3.2Te0.8O6.4 crystals in this glass, which is thought to decrease the distance between the Er3+ ions leading to an increase in the intensity of the upconversion and mid-infrared emissions.publishedVersionPeer reviewe

Síntesis y caracterización de vidrios, vitrocerámicos, y vidrios en lámina delgadas de fluoroteluritos dopados con tierras raras para aplicaciones fotónicas activas

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física de Materiales. Fecha de lectura: 02-07-201

Superbroadband near-infrared emission and energy transfer in Pr³⁺-Er³⁺ codoped fluorotellurite glasses

Author name used in this publication: Yuen H. Tsang2011-2012 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Upconverting luminescent materials for solar energy conversion

As attractive energy converters, solar cells are considered to play a vital role in covering the constantly increasing energy demands in the future. Despite the strong success in the field, a variety of solar cells including the commercially available ones are utilizing mainly the visible region of the solar spectrum, and thus are lacking the capacity to exploit effectively the infrared region. This issue gives a possibility to improve the solar cell efficiencies by using the unutilized energy of the infrared radiation. One solution to overcome this issue is to use upconverting luminescent materials which are capable of converting infrared radiation to visible by stacking photons. However, despite the potential, the rather weak conversion efficiency still limits the use of these materials. On the other hand, even small portions of this converted radiation would have significant effect on the solar cell efficiency which is why the development of these materials is desirable. The main aims of this thesis work were to investigate and develop different fabrication methods and properties of the upconverting materials that could be used in solar cells. These methods included the co-precipitation method to prepare crystalline inorganic upconverting fluoride materials, the atomic and the molecular layer deposition techniques to fabricate upconverting oxide and hybrid thin films, and the direct particles doping method for preparation of upconverting luminescent glasses. In addition, another goal was to study the possibilities to enhance the upconversion luminescence which was done by adding transition metal ions (Cr3+ or Mnn+) into the Yb3+ and Er3+ doped fluoride material. Improvement in the upconversion luminescence intensity was obtained by using Cr3+ ions. Another enhancement possibility is to use efficient NIR absorbers together with a strong upconverting lanthanide ion. The combined ALD/MLD technique was shown to enable the combination of NIR harvesting organic moiety and upconverting lanthanide ions to form a hybrid thin film. The ALD and the combined ALD/MLD techniques were demonstrated to be well suitable for upconverting thin film fabrication. Moreover, the direct particles doping method was shown to offer a promising way to introduce a variety of crystalline luminescent materials into different glass matrices.Käänteisviritteiset luminoivat materiaalit aurinkoenergian hyödyntämisessä Aurinkoenergian tarjoamia mahdollisuuksia pidetään yhtenä lupaavimmista vaihtoehdoista kasvavien energiatarpeiden täyttämisessä tulevaisuudessa. Aurinkokennot ovat kehittyneet paljon viime aikoina, mutta silti suurin osa tutkituista ja kaupallisesti saatavilla olevista aurinkokennoista pystyy hyödyntämään auringon spektristä vain näkyvän valon alueen jättäen infrapuna-alueen lähes kokonaan hyödyntämättä. Tämä ongelma tarjoaa mahdollisuuden parantaa aurinkokennojen tehokkuutta. Yksi tapa hyödyntää infrapunasäteilyn energiaa on käyttää käänteisviritteisiä luminoivia materiaaleja, jotka pystyvät muuntamaan infrapunasäteilyä näkyväksi valoksi pinoamalla fotoneja. Tämän prosessin heikko teho rajoittaa toistaiseksi materiaalien käyttöä. Toisaalta, jopa pienellä IR-säteilyn muuntomäärällä on mahdollisuus vaikuttaa merkittävästi aurinkokennon tehokkuuteen, minkä vuoksi materiaalien kehittäminen on herättänyt kiinnostusta. Väitöskirjatyön tavoitteena oli tutkia ja kehittää aurinkokennoissa mahdollisesti käytettävien käänteisviritteisten materiaalien ominaisuuksia ja valmistusmenetelmiä. Menetelmiin kuului kerasaostusmenetelmä, jolla valmistettiin kiteisiä fluoridimateriaaleja; atomi- ja molekyylikerroskasvatusmenetelmät, joilla valmistettiin kiteisiä oksidi ja amorfisia hybridiohutkalvoja; sekä seostusmetelemä luminoivien lasien valmistukseen. Lisäksi tavoitteena oli tutkia mahdollisuuksia parantaa käänteisviritteistä luminesenssia käyttämällä siirtymämetalli-ioneja (Cr3+ ja Mnn+). Käänteisviritteisen luminesenssin intensiteettiä kasvatettiin lisäämällä Cr3+ - ioneja fluoridimateriaaliin, joka oli seostettu Yb3+ ja Er3+ -ioneilla. Käänteisviritteisen luminesenssin tehostamisessa voidaan hyödyntää myös tehokkaasti NIR-säteilyä absorboivan orgaanisen osan yhdistämistä käänteisviritteisesti luminoivaan lantanidi-ioniin. Näiden osien yhdistäminen todettiin olevan mahdollista yhdistetyllä ALD/MLD -tekniikalla, jolla valmistettiin hybridikalvoja. Tämän yhdistetyn tekniikan ja ALD-tekniikan osoitettiin olevan hyvin käyttökelpoisia käänteisviritteisten kalvojen valmistuksessa. Lasimateriaaleilla tutkitun seostusmenetelmän osoitettiin olevan lupaava menetelmä erilaisten luminoivien kiteisten materiaalien lisäämisessä lasiin

Spectroscopic properties of Er3+ doped germanate glasses before and after a heat treatment process

In this paper structural, thermal and optical properties of Er3+ doped germanate glasses with the composition of 63.0GeO2-9.8Ga2O3-11.1BaO-4.9X-8.8Na2O-2.5Er2O3 (in mol%), where X = ZnO, TiO2, Al2O3 and Y2O3 are reported. The investigated glasses exhibit low phonon energies (<1000 cm−1) and high glass transition temperature varying between 588 and 642 °C. The Raman spectra evidence about different polymerization degree of the glasses. The thermal treatment leads to the precipitation of various crystals, the composition of which depends on the glass composition. According to the spectroscopic properties Er3+ ions are suspected to have similar local environment in the as-prepared glasses. However, Er-doped crystals are expected to precipitate upon devitrification, which leads to significant change of the spectroscopic properties, in particular increase in the intensity of upconversion and MIR emissions is observed. It is demonstrated that the glasses with Y2O3, ZnO and TiO2 are promising glasses especially for MIR applications.publishedVersionPeer reviewe

Optical fibre thermometry using ratiometric green emission of an upconverting nanoparticle- polydimethylsiloxane composite

The thermally coupled green band emission from excited Er 3+ ions has been used in the past to create optical thermometers, by doping the material in various types of media, particularly glasses. Glasses are known to be excellent hosts for Er 3+ ions: however, high temperatures (>900 K) are usually required for doping these ions into glasses and a non-linear temperature response is often produced. In this work, the frequently encountered drawbacks of glass-based temperature sensors have been addressed by developing a temperature sensor created at a lower temperature (543 K), by dip-coating chemically synthesized upconverting nanoparticles (UCNP-NaYF4:(18%) Yb 3+ , (2%) Er 3+) embedded in polydimethylsiloxane (PDMS) onto the tip of a 1000 μm optical fibre, to create the actual fibre probe. The sensor shows an excellent linear response (R 2 = 0.991) over a very useful temperature range of 295 K-473 K, with a sensitivity of 2.9 ×10-3 K-1 , a temperature resolution of ± 2.7 K and response time of ~ 5 seconds. Additionally, a probe was investigated 2 where a pure upconverting nanoparticle powder was coated on the tip of optical fibre and its spectral and temperature response was obtained (and cross compared with that of UCNP-PDMS composite). The results obtained from the probe development work show that the UCNP-PDMS-coated optical fibre temperature sensor developed offers a better alternative to more conventional Er 3+ doped glass-based temperature sensors, in terms of the thermal budget, the synthesis process and the ease of coating, creating as a result, a very linear device response

Structural and optical properties of silver and titanium nanoparticles co-embedded magnesium-zinc-sulfophosphate glass with neodymium doping

Demand of high emission cross-section laser amplifier is ever-increasing. The rare earth ions (REIs) doped magnesium zinc sulfophosphate (PMZ) glasses with noble metal nanoparticles (NPs) inclusion were shown potential as laser host. This study reported that the emission/absorption traits of these REIs inside the glass matrix could be improved using the NPs which enabled localized surface plasmon resonance (LSPR). The LSPR produces strong local electric field (LEF) in the vicinity of the REIs. The melt-quenching method was used to synthesize glass composition 58.5P2O5-20.0MgO-20.0ZnSO4-1.5 Nd2O3-yAg NPs-zTi NPs mol% where y and z could be in the range of 0.0-1.5 mol%. The co-embedment of two types of metal NPs inside the glass could provide flexibility to customize the generated LEF strength in the proximity of the REIs. The X-ray diffraction (XRD) analyses confirmed the amorphous nature of the as-quenched samples. The high-resolution transmission electron microscopy (HRTEM) images showed the nucleation of both Ag and Ti3O5 NPs inside the glass matrix. The nucleation of Ti into Ti3O5 NPs occurred via two-step Finke-Watzky mechanism. Both the Fourier transform infrared (FTIR) and Raman spectral analyses confirmed an insignificant structural change from the incorporation of the NPs into the glass matrix. The observed LSPR band of the Ag (?442 nm) and Ti3O5 (?588 and 774 nm) NPs verified their successful embedment into the host matrix. The ultraviolet-visible-near infrared (UV-Vis-NIR) absorption spectra of the glasses exhibited twelve characteristic absorption bands of Nd3+. The photoluminescence (PL) emission spectra of the prepared glasses disclosed a prominent yellow band around 585 nm, corresponding to the transition of 2G7/2+4G5/2?4I9/2 in Nd3+. The coupling of Ag and Ti NPs into the glass at a certain concentration could lead to PL intensity quenching. This ascribed to the local heating effect of Ti3O5 NPs. The Judd-Ofelt intensity and radiative parameters were calculated from the absorption and PL spectral data. The PMZ1.5Nd04Ti0.3Ag glass sample showed the highest stimulated emission cross-section of 4.78×10–24 cm2. The results suggested that the co-embedment of metal NPs into glass could be an innovative strategy to tailor the spectroscopic characteristics of the glasses which is potential for photonic and solid-state laser applications

Silver nanoparticle enhanced the optical properties of the rare earth doped magnesium-zinc-sulfophosphate glass

Magnesium-zinc-sulfophosphate (P2O5-MgO-ZnSO4) glasses being a prospective host for lasing active media require precise composition optimization and systematic characterization. A series of glass samples in the composition of (60.0- x)P2O5-20.0MgO-20.0ZnSO4-xRE2O3 (0.0 ≤ x≤ 2.0 mol% and rare earth (RE) = Sm, Dy, and Er), (59.5-y)P2O5-20.0MgO-20.0ZnSO4-0.5RE2O3-yAgCl (0.0 ≤ y ≤ 0.5 mol% and RE = Sm and Dy) and (59.5-z)P2O5-20.0MgO-20.0ZnSO4-0.5Er2O3-zAgCl (0.0 ≤ z≤ 1.5 mol%) were synthesized using melt-quenching technique. The samples were thoroughly characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR), ultraviolet-visible (UV-Vis) absorption, photoluminescence (PL) and Raman spectroscopy. XRD verified the samples amorphous nature and TEM images manifested the nucleation of homogeneously distributed spherical silver (Ag) nanoparticles in the glass matrix. FTIR spectra revealed the bonding vibrations for P-O bonds, P-O-P linkages, and PO2 units. There is no evidence in Raman spectra of RE (RE= Sm, Dy and Er) doped P2O5- MgO-ZnSO4 glasses to confirm the incorporation of the sulfate ions to the network formation. The absorption spectrum of RE (RE = Sm, Dy and Er) doped P2O5-MgOZnSO4 glasses with and without incorporation of Ag nanoparticles is originated from electronic transitions from the ground level to various excited levels belonging to the 4f9 electronic configuration of the RE ions. Absorption and emission spectra are used to evaluate the Judd-Ofelt (JO) intensity parameters and radiative transition probabilities, branching ratios and stimulated emission cross-sections of the three RE ion (RE = Sm, Dy, and Er) doped glass systems. The room temperature PL spectra of samarium-doped glass revealed four emission peaks centered at around 562, 599, 644, and 702 nm, which are assigned to the transitions from 4G5/2 to 6H5/2, 6H7/2, 6H9/2 and 6H11/2, respectively. The PL spectra of dysprosium-doped glass displayed two prominent peaks at around 480 nm and 574 nm corresponding to the 4F9/2→6H15/2 and 4F9/2→6H13/2 transitions, respectively and two weak peaks. Conversely, erbium-doped glass system exhibited two strong emission peaks centered at around 541 nm and 654 nm attributed to the 4S3/2→4I15/2 and 4F9/2→4I15/2 transitions, respectively. All glass series containing Ag nanoparticles showed considerable emission intensity enhancement, which is attributed to the nanoparticle surface plasmon resonance mediated intensified local field effect in the proximity of RE ions. Overall properties of each glass series are demonstrated to be modified due to the embedment of Ag nanoparticles. Among all the glass series produced, the stimulated emission crosssection for 4S3/2→4I15/2 transition in erbium-doped glass system is discerned to be the highest