13451-05-3Relevant articles and documents
Synthesis, structures and temperature-induced phase transitions of the Sr2Cd1-xCaxWO6 (0 ≤ x ≤ 1) double perovskite tungsten oxides
Faik,Igartua,Pizarro
, p. 196 - 201 (2009)
The solid solution with double perovskite structure and general chemical formula Sr2Cd1-xCaxWO6 (0 ≤ x ≤ 1) has been synthesized by the co-precipitation method. The Cd2+ cation substitution by Ca
Controllable synthesis of hierarchical nanostructures of CaWO4 and SrWO4 via a facile low-temperature route
Chen,Gong,Zhu,Yuan,Qian,Qian
, p. 45 - 50 (2009)
CaWO4 and SrWO4 nanostructures have been synthesized via a simple microemulsion-mediated route. With careful control of the fundamental experimental parameters including the concentration of reactants, the reaction time and the tempe
Structural and thermal investigations of Sr2WO5
Keskar, Meera,Sali,Vats,Phatak,Krishnan,Kannan
, p. 3639 - 3647 (2017)
The crystal structure of Sr2WO5has been refined using powder X-Ray diffraction (XRD) and neutron diffraction (ND) data. The corner connected WO6octahedra forms infinite cis-bridged chains along b axis which are further connected by the layer of Sr atoms to give a three dimensional network. Thermogravimetric study revealed that Sr2WO5on storage picks up moisture from the surrounding to give a mixture of Sr(OH)2and SrWO4. Percentage of Sr(OH)2in Sr2WO5increases with increase of storage time under normal atmospheric condition. The hydrated compound on heating up to 1473?K again yield back Sr2WO5. High Temperature X-ray Diffraction (HTXRD) studies of Sr2WO5and SrWO4in vacuum showed positive thermal expansion in the temperature range of 298–1273?K. Thermogram of Sr2WO5recorded with Differential Scanning Calorimeter (DSC) showed a reversible phase transition at 423?K. Specific heat capacity of Sr2WO5was measured between temperature 463–863?K using heat flux DSC.
Room-temperature preparation of crystallized luminescent Sr1-xCaxWO4 solid-solution films by an electrochemical method
Cho, Woo-Seok,Yashima, Masatomo,Kakihana, Masato,Kudo, Akihiko,Sakata, Tadayoshi,Yoshimura, Masahiro
, p. 137 - 139 (1996)
A complete series of well-crystallized solid-solution oxide films, Sr1-XCaXWO4 (0≤X≤1), has been prepared on a tungsten substrate in the electrolytic solution containing Sr2+ and Ca2+ ions by an electrochemical method at room temperature (25°C). The composition of solid-solution oxide films could easily be controlled by the concentrations of Sr and Ca species in the starting solutions. The films showed only single blue emission at liquid nitrogen temperature (-196°C), strongly suggesting that they consisted of well-crystallized defect-free crystals.
PREPARATION OF CUBIC PEROVSKITES A(B2/5W3/5)O3 (A equals Ba OR Sr, B equals Na OR Li).
Hikichi,Suzuki
, p. c. 99-c. 100 (1987)
Pure cubic perovskites Ba(Na//2/////5W//3/////5)O//3, Sr(Na//2/////5W//3/////5)O//3 were prepared by solid-state reaction at 600 degree to 650 degree C in air, by starting with oxides or carbonates of the various elements. The cubic forms have an ordered arrangement of the B cations in the ABO//3 structure.
Synthesis, characterization and novel photoluminescence of SrWO4:Ln3+ nanocrystals
Xu, Bingyu,Li, Mingxia,Pan, Kai,Li, Rong,Fan, Naiying,Wang, Guofeng
, p. 3522 - 3526 (2016)
SrWO4:Ln3+ (Ln = Eu, Ce, and Tb) nanocrystals were successfully synthesized by a hydrothermal method, and were characterized by X-ray diffraction, transmission electron microscopy, and scanning electron microscopy. The results indicated that the crystalline size of nanocrystals decreases with increasing Eu3+ concentrations and increases with increasing annealing temperature, gradually. The photoluminescence properties of SrWO4:Ln3+ were investigated in detail. In the emission spectra of SrWO4:Eu3+, the luminescence was dominated by 5D0 → 7F2 transition, indicating that Eu3+ occupied a site lacking inversion symmetry. The concentration quenching effect hardly occurs. In the excitation spectra of SrWO4:Eu3+ nanocrystals monitored at 619 nm, the most intense peak is centered at 467 nm when the Eu3+ concentration was less than 10%, while the most intense peak is centered at 396 nm when the Eu3+ concentration was 15%. In the normalized emission spectra of SrWO4:Ce3+/Tb3+ nanocrystals excited at 254 nm, the intensity ratio of the sharp emission peaks from Tb3+ ions to the broad emission band from Ce3+ ions increased with increasing Tb3+ concentration.
Two-step synthesis and visible-light-driven photocatalytic water oxidation activity of AW(O,N)3 (A = Sr, La, Pr, Nd and Eu) perovskites
Kawashima, Kenta,Hojamberdiev, Mirabbos,Wagata, Hajime,Zahedi, Ehsan,Yubuta, Kunio,Domen, Kazunari,Teshima, Katsuya
, p. 29 - 37 (2016)
To expand the family of transition metal oxynitride perovskites, the two-step synthesis of a series of tungsten-based metal oxynitride perovskites (EuW(O,N)3, NdW(O,N)3, PrW(O,N)3, LaW(O,N)3, and SrW(O,N)3) and their visible-light-driven photocatalytic water oxidation activity with the assistance of CoOx (2 wt% Co) cocatalyst were studied in this work. The XRD results revealed that the cubic perovskite LnW(O,N)3 (Ln = Pr, Nd, and Eu) and SrW(O,N)3 phases and tetragonal perovskite LaW(O,N)3 phase were successfully synthesized by nitriding their corresponding oxide precursors at 900 °C for 10–25 h under an NH3 flow, with minor secondary phases in only PrW(O,N)3 and NdW(O,N)3. The highly porous structures of EuW(O,N)3, LaW(O,N)3, and SrW(O,N)3 were formed from the segregation of nanocrystals with average sizes of 140, 92, and 160 nm, respectively. The surfaces of the NdW(O,N)3 and PrW(O,N)3 crystal structures were covered with plate-like crystals which can be identified as W5N4. No clear absorption edges were observed in the UV–Vis diffuse reflectance spectra of the tungsten-based metal oxynitrides owing to the extensive amount of reduced tungsten species (W5+ and W4+) or metallic tungsten and anion deficiency. Within 5 h of the photocatalytic water oxidation half-reaction, the CoOx-loaded SrW(O,N)3 crystal structures exhibited the highest photostability and O2 evolution rate of 3.3 μmol h?1 compared with CoOx-loaded LnW(O,N)3 (Ln = La, Pr, Nd, and Eu) crystal structures due possibly to the highest O/N ratio and more positively positioned top of valence band of SrW(O,N)3. The present work is expected to stimulate research into the development of more stable and efficient tungsten-based metal oxynitride perovskites in the future.
Low-temperature synthesis of metal tungstates nanocrystallites in ethylene glycol
Chen, Di,Shen, Guozhen,Tang, Kaibin,Zheng, Huagui,Qian, Yitai
, p. 1783 - 1789 (2003)
In this paper, we report the low-temperature synthesis of metal tungstate, MWO4 (M=Ca, Sr, Ba, Cd, Zn, Pb) nanocrystallites. By reaction between metal chloride and sodium tungstate in ethylene glycol at 180°C for 10h, well-crystallized tungstate particles were successfully obtained. Characterization by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) shows that the product powders consist of nanosize particles. Photoluminescence measurement reveals that the as-obtained CaWO4, CdWO4, and PbWO4 show excitonic peaks at about 430, 500 and 500nm, respectively. The solvent and reaction conditions are important in the formation of the products.
Chloride Flux Growth of Idiomorphic AWO4 (A = Sr, Ba) Single Microcrystals
Kawashima, Kenta,Kim, Jun-Hyuk,Cheng, Isabelle,Yubuta, Kunio,Shin, Kihyun,Liu, Yang,Lin, Jie,Henkelman, Graeme,Mullins, C. Buddie
, p. 5301 - 5310 (2018)
Scheelite-type divalent metal tungstate materials (AWO4) have been studied for various applications due to their attractive mechanical and chemical properties. Preparation of the shape-controlled AWO4 crystals with high crystallinity is one of the most effective approaches for further exploring and improving their properties. In this study, highly crystalline SrWO4 and BaWO4 microcrystals with different morphologies were grown by using a chloride flux growth technique. To investigate the effect of growth conditions on SrWO4 and BaWO4 crystals, NaCl and KCl were used as a flux, and the solute concentration was adjusted in the range of 5-50 mol %. The difference in the flux cation species (Na+ and K+) mainly affected the crystal size. In accordance with increasing the solute concentration, the dominant crystal shape of SrWO4 and BaWO4 varied as follows: whisker (a rod- or wire-like morphology with a large aspect ratio) → platelet → well/less-faceted polyhedron. Additionally, according to scanning electron microscopy and transmission electron microscopy results, a dendritic morphological transformation from AWO4 whisker to platelet during crystal growth has been proposed.
Crystal structures and temperature-induced phase transitions of Sr2 Mn2 + W6 + O6, and of its transformation to Sr2 Mn3 + W6 + O6 + δ
Faik,Igartua,Cuello,Jiménez-Villacorta,Castro,Lezama
, p. 53 - 62 (2009)
We present a new effective method for synthesizing Sr2 MWO6 double perovskite oxides: the co-precipitation route at 1220 K in nitrogen environment. Using conventional X-ray diffraction methods, we have confirmed the room-temperature
A novel orange emissive phosphor SrWO4:Sm3+ for white light-emitting diodes
Ju, Zheng-Hua,Wei, Rui-Ping,Ma, Jing-Xin,Pang, Chao-Ran,Liu, Wei-Sheng
, p. 133 - 136 (2010)
A novel orange emissive phosphor, Sm3+-doped SrWO4, was synthesized by high temperature solid-state reaction in air atmosphere. The excitation spectra show that the phosphors can be efficiently excited by ultraviolet and near-ultraviolet light, the optimized concentration is 4 mol%. Three emission peaks locate at 562, 596 and 642 nm, corresponding to CIE chromaticity coordinates of (x = 0.54, y = 0.46), which indicates the orange light emitting. The decay curves are well fitted with triple-exponential decay models. The quantum yield of the Sr0.96Sm0.04WO 4 phosphor is about 70.65% under excitation of 377 nm. Furthermore, the temperature-dependent luminescence indicates the phosphor exhibits a small thermal-quenching property. So the phosphor is able to be applied to UV-LED chip-based white light-emitting diodes.
Luminescence and absorbance of highly crystalline CaMoO4, SrMoO4, CaWO4 and SrWO4 nanoparticles synthesized by co-precipitation method at room temperature
Thongtem, Titipun,Kungwankunakorn, Sukjit,Kuntalue, Budsabong,Phuruangrat, Anukorn,Thongtem, Somchai
, p. 475 - 481 (2010)
Highly crystalline CaMoO4, SrMoO4, CaWO4 and SrWO4 nanoparticles were successfully synthesized by the co-precipitation of mixtures of Ca(NO3)24H2O or Sr(NO3)2/su
Scheelite-type MWO4 (M = Ca, Sr, and Ba) nanophosphors: Facile synthesis, structural characterization, photoluminescence, and photocatalytic properties
Shivakumara,Saraf, Rohit,Behera, Sukanti,Dhananjaya,Nagabhushana
, p. 422 - 432 (2015)
Scheelite-type MWO4 (M = Ca, Sr, and Ba) nanophosphors were synthesized by the precipitation method. All compounds crystallized in the tetragonal structure with space group I41/a (No. 88). Scherrer's and TEM results revealed that the average crystallite size varies from 32 to 55 nm. FE-SEM illustrate the spherical (CaWO4), bouquet (SrWO4), and fish (BaWO4) like morphologies. PL spectra indicate the broad emission peak maximum at 436 (CaWO4), 440 (SrWO4), and 433 nm (BaWO4) under UV excitation. The calculated CIE color coordinates of MWO4 nanophosphors are close to the commercial BAM and National Television System Committee blue phosphor. The photocatalytic activities of MWO4 were investigated for the degradation of methylene blue dye under UV illumination. At pH 3, BaWO4 nanocatalyst showed 100% dye degradation within 60 min. The photocatalytic activity was in the decreasing order of BaWO4 > CaWO4 > SrWO4 under both neutral and acidic conditions.
Observation of chemical reactions between alkaline-earth oxides and tungsten at high pressure and high temperature
Errandonea, Daniel
, p. 1117 - 1120 (2009)
The potential chemical reactions of alkaline-earth oxides (AeO with Ae: Mg, Ca, Sr, and Ba) and tungsten are studied at high pressure and high temperature. At pressures ranging from 5 to 10 GPa and temperatures of 2000 K, a noticeable reaction between AeO
Electronic band structures and photovoltaic properties of MWO4 (M=Zn, Mg, Ca, Sr) compounds
Kim, Dong Wook,Cho, In-Sun,Shin, Seong Sik,Lee, Sangwook,Noh, Tae Hoon,Kim, Dong Hoe,Jung, Hyun Suk,Hong, Kug Sun
, p. 2103 - 2107 (2011)
Divalent metal tungstates, MWO4, with wolframite (M=Zn and Mg) and scheelite (M=Ca and Sr) structures were prepared using a conventional solid state reaction method. Their electronic band structures were investigated by a combination of electronic band structure calculations and electrochemical measurements. From these investigations, it was found that the band structures (i.e. band positions and band gaps) of the divalent metal tungstates were significantly influenced by their crystal structural environments, such as the WO bond length. Their photovoltaic properties were evaluated by applying to the working electrodes for dye-sensitized solar cells. The dye-sensitized solar cells employing the wolframite-structured metal tungstates (ZnWO4 and MgWO4) exhibited better performance than those using the scheelite-structured metal tungstates (CaWO4 and SrWO4), which was attributed to their enhanced electron transfer resulting from their appropriate band positions.
Synthesis, characterization, and microwave dielectric properties of Sr 2-xLa2Mg1+xW2O12 (x=0, 1) ceramics
Venugopal, Vineeth,Anjana, Prabhakaran Sreekumari,Parkash, Om,Kumar, Devendra,Sebastian, Mailadil Thomas
, p. 2467 - 2469 (2010)
SrLa2Mg2W2O12 and Sr 2La2MgW2O12 ceramics were prepared by the conventional solid-state ceramic route and their dielectric properties were investigated in the radio an
Fine-Grained Tungstates SrWO4 and NaNd(WO4)2 with the Scheelite Structure Prepared by Spark Plasma Sintering
Potanina,Orlova,Nokhrin,Mikhailov,Boldin,Sakharov,Belkin,Lantsev,Tokarev,Chuvil’deev
, p. 296 - 302 (2019)
Fine-grained SrWO4 and NaNd(WO4)2 ceramics with the scheelite structure having high relative densities (99 and 95.8%), which can appear candidate matrices for radioactive waste (RAW) management, are prepared by spark plasma sintering (SPS). The phase identity of the ceramics is determined by X-ray powder diffraction; their microstructure is studied by X-ray photoelectron spectroscopy. The tungstates under study are sintered at rather low temperatures (580–665°C). The intensity of compaction of the tungstates at the early sintering stage is determined by the degree of powder agglomeration. The activation energy of fine-grained scheelite ceramics at high temperatures corresponds with the activation energy of grain-boundary oxygen diffusion.
Photoluminescence in the CaxSr1-xWO4 system at room temperature
Porto,Longo,Pizani,Boschi,Simoes,Lima,Ferreira,Soledade,Espinoza,Cassia-Santos,Maurera,Paskocimas,Santos,Souza
, p. 1876 - 1881 (2008)
In this work, a study was undertaken about the structural and photoluminescent properties, at room temperature, of powder samples from the CaxSr1-xWO4 (x=0-1.0) system, synthesized by a soft chemical method and heat treated between 400 and 700 °C. The material was characterized using Infrared, UV-vis and Raman spectroscopy and XRD. The most intense PL emission was obtained for the sample calcined at 600 °C, which is neither highly disordered (400-500 °C), nor completely ordered (700 °C). Corroborating the role of disorder in the PL phenomenon, the most intense PL response was not observed for pure CaWO4 or SrWO4, but for Ca0.6Sr0.4WO4. The PL emission spectra could be separated into two Gaussian curves. The lower wavelength peak is placed around 530 nm, and the higher wavelength peak at about 690 nm. Similar results were reported in the literature for both CaWO4 and SrWO4.
Activated H2O2 on Ag/SiO2–SrWO4 surface for enhanced dark and visible-light removal of methylene blue and p-nitrophenol
El-Kemary, Maged,El-Sheshtawy, Hamdy S.,Shoueir, Kamel R.,ghubish, Zaynab
, (2020)
Activated H2O2 on the surface of nanostructures for advanced oxidation process attracts the interest for energy consumption, time saving rather than Fenton reaction process. Here, we introduce Ag/SiO2 NPs immobilized on Sr
Chemical Interactions in Na+,Sr2+||Cl–, EO2-4 (E = Mo,W) and Na+,Sr2+||Cl–, MoO2-4, WO2-4 Reciprocal Systems: Description and Study
Burchakov, A. V.,Garkushin, I. K.,Milov, S. N.,Sukharenko, M. A.,Verdiev, N. N.
, (2020)
Abstract: Chemical interactions of salts in the four-component reciprocal system comprised of chlorides, molybdates, and tungstates of sodium and strontium are studied by the ion-balance method. DTA heating curves feature exotherms due to the interaction
Host composition dependent tuneable morphology and luminescent property of the CaXSrYBa1?X?YWO4:RE3+(RE=Pr, Ho, and Er) phosphors
Li, Linlin,Wu, Hong-Yue
, p. 106 - 119 (2017)
Novel Pr3+, Ho3+, and Er3+single-doped CaXSrYBa1?X?YWO4phosphors were successfully prepared via a facile hydrothermal method. The hydrothermal process was conducted in aqueous condition without the use of any organic solvent, surfactant, or catalyst. The effects of doping-host composition and RE3+doping concentration on the emission intensity were investigated to optimize the luminescent properties of CaXSrYBa1?X?YWO4:RE3+phosphors. Experimental results demonstrate that the morphologies of the products vary gradually and regularly with the change of the host composition, in which the anisotropic growth played a key role. Moreover, the down-conversion emissions of Pr3+, Ho3+, and Er3+in CaXSrYBa1?X?YWO4host were successfully realized. After optimizing the luminescent properties, Ca0.4Sr0.6WO4:0.01Pr3+, Ca0.8Sr0.2WO4:0.01Ho3+, and Ca0.6Sr0.4WO4:0.005Er3+exhibited optimal luminescent property, with orange, yellowish-green, and green emissions, respectively.
Dielectric and microstructural study of the SrWO4, BaWO 4, and CaWO4 scheelite ceramics
Krzmanc, Marjeta MacEk,Logar, Manca,Budic, Bojan,Suvorov, Danilo
, p. 2464 - 2472 (2011)
MWO4 (M=Ca, Sr and Ba) scheelite ceramics were studied in terms of their syntheses, sintering, solubility in water, and dielectric response after storing them in dry and moist atmospheres. Of the studied scheelites, the CaWO4 possessed the most promising dielectric properties (ε=10.9, Q × f=105 600 GHz), which were stable under the influence of humidity. BaWO4 and SrWO4 exhibited ε=9.0 and Q × f values of 32 200 and 62 600 GHz, respectively. The most detrimental effect of the moisture was observed for SrWO4. A sodium impurity present in the SrCO3 reagent (0.35 wt%), which was used for the synthesis of the SrWO4, was found to lower the sintering temperature, enhance the grain growth, and change the other properties of the ceramics, such as humidity susceptibility and solubility in water. The evident tendency of the ceramics to attract water and the increased dissolution of tungstate were observed for all MWO4 scheelite ceramics, which were sintered with the help of Na2CO3 or Li2CO3 (0.5 wt%) sintering aids. The results of the present study suggest that the physical and chemical properties of the ceramics should be carefully considered in the case of using of alkaline-containing sintering aids.
Deciphering the Role of Charge Compensator in Optical Properties of SrWO4:Eu3+:A (A = Li+, Na+, K+): Spectroscopic Insight Using Photoluminescence, Positron Annihilation, and X-ray Absorption
Gupta, Santosh Kumar,Sudarshan, Kathi,Yadav, Ashok Kumar,Gupta, Ruma,Bhattacharyya, Dibyendu,Jha, Shambhu Nath,Kadam, Ramakant Mahadeo
, p. 821 - 832 (2018)
Studies have been carried out to understand the specific role of the alkali charge compensator on the luminescence properties of an alkali ion (Li+, Na+, and K+) codoped SrWO4:Eu phosphor. The oxidation state of the europium ion was found to be +3 on the basis of X-ray absorption near edge structure (XANES) measurements. This is the first report of its kind where opposite effects of Li+ ion and Na+/K+ ions on photoluminescence intensity have been observed. Li+ ion codoping enhanced the photoluminescence intensity from SrWO4:Eu3+ phosphor while Na+/K+ ion codoping did not. On the other hand, the luminescence lifetime is maximum for the Na+ ion codoped sample and minimum for the Li+ ion codoped sample. The results could be explained successfully using time-resolved luminescence, positron annihilation lifetime spectroscopy (PALS), and extended X-ray absorption fine structure (EXAFS) spectroscopy measurements. Changes in the Eu-O bond length and Debye-Waller Factor (σ2) upon Li+/Na+/K+ codoping were monitored through EXAFS measurements. PALS also highlighted the fact that Li+ codoping is not contributing to reduction in the cation vacancies and might be occupying interstitial sites rather than lattice positions due to its very small size. On europium doping there is lowering in symmetry of SrO8 polyhedra from S4 to C6, which is reflected in an intense electric dipole transition in comparison to the magnetic dipole transition. This is also corroborated using trends in Judd-Ofelt parameters. The results have shown that the luminescence lifetime is better when the vacancy concentration is lower as induced by Na+ and K+ codoping, while the emission intensity is higher in the samples when distortion around Eu3+ is reduced as induced by Li+ codoping.
Structure and calorimetric study of complex oxides based on lanthanum, tungsten, and alkaline earth elements MeLa2WO7 (Me = Mg, Ca, Sr, Ba)
Bissengaliyeva, Mira R.,Zhakupov, Ramazan M.,Knyazev, Alexander V.,Gogol, Daniil B.,Taimassova, Shynar T.,Balbekova, Bakhyt K.,Bekturganov, Nuraly S.
, p. 2287 - 2301 (2020/01/28)
As a result of citrate synthesis by the “sol–gel” method, we obtained samples of the compounds of ternary oxides with lanthanum, tungsten, and alkaline earth elements with the general formula MeLa2WO7 (Me = Mg, Ca, Sr, Ba). The structure of the samples obtained was studied by the X-ray diffraction, electron probe, and X-ray spectral microanalysis; the infrared and Raman spectra of the compounds were obtained. The results of indexing for SrLa2WO7 and BaLa2WO7 are in good agreement with the previously published crystallographic data. The heat capacity of the samples was measured by using of adiabatic calorimetry and their thermodynamic functions were calculated.
Role of alkali charge compensation in the luminescence of CaWO4:Nd3+ and SrWO4:Nd3+ Scheelites
Das, Debarati,Datrik, C. S.,Gupta, Santosh K.,Nandi, P.,Sudarshan, K.
, p. 7300 - 7309 (2020/06/18)
This work presents a new perspective on alkali metal co-doped rare earth based-phosphors in understanding the distinct role of 3 different alkali metal co-dopants, Li+, Na+ and K+, with the excitation of host and rare earth dopant. The system under investigation is the technologically important Scheelite host and NIR-emitting Nd3+ ion. The Li+ ion was found to improve the crystallinity and reduce the symmetry more efficiently than act as a sensitizer in aiding the host to dopant energy transfer, which results in more emission output from the Nd3+ excitation in comparison to the host. We could also successfully compare the optical output of CaWO4:Nd3+ and SrWO4:Nd3+ Scheelite with and without alkali metal ions in terms of the peak shift and intensity by considering the greater lattice dimensions of the latter when compared to the former. For the larger SrWO4:Nd3+ lattice, K+ and Na+ were found to be better co-dopants in enhancing the NIR emission under the host and Nd3+ excitation, respectively, compared to the smaller Li+ ion. The smaller unit cell dimensions of CaWO4 might facilitate more efficient energy and relaxation processes, making its excited state lifetime shorter in comparison to that of doped SrWO4. For alkali ion co-doping, a higher PL lifetime was observed for Li doping in the case of CaWO4 and Na co-doping in the case of SrWO4 under Nd3+ excitation, which is well in line with the NIR emission spectroscopy. Positron annihilation lifetime spectroscopy suggested the formation of cation vacancies and other associated vacancy clusters in the Nd3+ aliovalent doped CaWO4. Li+ does not act as a charge compensator for the removal of cation vacancies created by Nd3+ substitution in the Ca lattice. On the other hand, Na+ and K+ act as good charge compensators in Nd3+ doping in terms of vacancy removal. This work is highly relevant in understanding the role of alkali co-doping in both the luminescence properties and formation of defects to produce efficient Scheelite-based NIR phosphors.
