Effect of B2O3 on the spectroscopic properties in Er3+/Ce3+ co-doped tellurite-niobium glass

The high phonon energy oxide of B2O3 is introduced into the Er3+/Ce3+co-doped tellurite-niobium glasses with composition of TeO2-Nb2O5-ZnO-Na2O.The absorption spectra,1.53 μm band fluorescence spectra,fluorescence lifetime and Raman spectra of Er3+in glass samples are measured together with the calculations of Judd-Ofelt spectroscopic parameter,stimulated emission and absorption cross-sections,which evaluate the effect of B2O3 on the 1.53 μm band spectroscopic properties of Er3+.It is shown that the introduction of an appropriate amount of B2O3 can further improve the 1.53 μm band fluorescence intensity through an enhanced phonon-assisted energy transfer(ET) between Er3+/Ce3+ions.The results indicate that the prepared Er3+/Ce3+co-doped tellurite-niobium glass with an appropriate amount of B2O3 is a potential gain medium for the 1.53 μm bandbroad erbium-doped fiber amplifier(EDFA).     

Improvement of 1.53 μm emission and energy transfer of Yb3+/Er3+ co-doped tellurite glass and fiber

To improve the 1.53 μm band emission of Er³⁺, the trivalent Yb³⁺ ions were introduced into the Er³⁺ single-doped tellurite glass with composition of TeO₂–ZnO–La₂O₃, a potential gain medium for Er³⁺-doped fiber amplifier (EDFA). The improved effects were investigated from the measured 1.53 μm band and visible band spontaneous emission spectra together with the calculated 1.53 μm band stimulated emission (signal gain) spectra under the excitation of 975 nm laser diode (LD). It was found that Yb³⁺/Er³⁺ co-doping scheme can remarkably improve the visible band up-conversion and the 1.53 μm band fluorescence emission intensity, and meanwhile improves the 1.53 μm band signal gain to some extent, which were attributed to the result of the effective energy transfer of Yb³⁺:²F_5/2 + Er³⁺:⁴I_15/2 → Yb³⁺:²F_7/2 + Er³⁺:⁴I_11/2. The quantitative study of energy transfer mechanism was performed and microscopic energy transfer parameters between the doped rare-earth ions were determined. In addition, the spectroscopic properties of Er³⁺ were also investigated from the measured absorption spectrum according to the Judd–Ofelt theory, and the structure behavior and thermal stability of the prepared tellurite glass were analyzed based on the X-ray diffraction (XRD) and differential scanning calorimeter (DSC) measurements, respectively.     

Improvement of 4I11/2 → 4I13/2 Transition Rate and Thermal Stabilities in Er3+‐Doped TeO2‐B2O3 (GeO2)‐ZnO‐K2O Glasses

Spectroscopic and thermal analysis indicates that tellurite glasses doped with B₂O₃ and GeO₂ are promising candidate host materials for wide‐band erbium doped fiber amplifier (EDFA) with a high 980 nm pump efficiency. In this study, we measured the thermal stabilities and the emission cross‐sections for Er³⁺: ⁴I _13/2 → ⁴I _15/2 transition in this tellurite glass system. We also determined the Judd‐Ofelt parameters and calculated the radiative transition rates and the multiphonon relaxation rates in this glass system. The 15 mol% substitution of B₂O₃ for TeO₂ in the Er³⁺‐doped 75TeO₂‐20ZnO‐5K₂O glass raised the multiphonon relaxation rate for ⁴I_11/2 → ⁴I_13/2 transition from 4960 s^?1 to 24700 s^?1, but shortened the lifetime of the ⁴I_13/2 level by 14 % and reduced the emission cross‐section for the ⁴I_13/2 → ⁴I_15/2 transition by 11%. The 15 mol% GeO₂ substitution in the same glass system also reduced the emission cross‐section but increased the lifetime by 7%. However, the multiphonon relaxation rate for ⁴I_11/2 → ⁴I_13/2 transition was raised merely by 1000 s^?1. Therefore, a mixed substitution of B₂O₃ and GeO₂ for TeO₂ was concluded to be suitable for the 980 nm pump efficiency and the fluorescence efficiency of ⁴I_13/2 → ⁴I_15/2 transition in Er³⁺‐doped tellurite glasses.     

Structure and spectroscopic properties of Er3+/Ce3+ co-doped TeO2-Bi2O3-TiO2 glasses modified with various WO3 contents for 1.53 μm emission

The Er^3＋/Ce^3＋ co-doped tellurite-based glasses （TeO2-Bi2O3-TiO2） modified with various WO3 contents are prepared using conventional melt-quenching technique. The X-ray diffraction （XRD） patterns and Raman spectra of glass sam- ples are measured to investigate the structures. The absorption spectra, the up-conversion emission spectra, the 1.53 /am band fluorescence spectra and the lifetime of Er3＋：4113/2 level are measured, and the amplification quality factors of Er3＋ are calculated to evaluate the effect of WO3 contents on the 1.53 μm band spectroscopic properties. With the in- troduction of WO3, it is found that the prepared tellurite-based glasses maintain the amorphous structure, while the 1.53 μm band fluorescence intensity of Er3＋ is improved evidently, and the fluorescence full width at half maximum （FWHM） is broadened accordingly. In addition, the prepared tellurite-based glass samples have larger bandwidth qual- ity factor than silicate and germanate glasses. The results indicate that the prepared Er3＋/Ce3＋ co-doped tellurite-based glass with a certain amount of WO3 is an excellent gain medium applied for the 1.53 μm band Er3＋-doped fiber ampli- fier （EDFA）.     

Annealing studies of photoluminescence spectra from multiple Er3+ centers in er-implanted GaN

A study of selectively excited photoluminescence (PL) at ∼ 6K in Er-im planted GaN as a function of annealing temperature (400–1000°C) has detected nine different Er³⁺ centers with distinct ∼ 1540 nm ⁴I_13/2 → ⁴I_15/2 Er³⁺ PL spectra and different activation temperatures. However, most of the optically active implanted Er atoms are incorporated at annealing temperatures as low as 400°C on a single type of center for which PL can only be excited efficiently by direct intra-4f shell absorption and is not strongly pumped by either above-gap or broad-band below-gap absorption. This strongly suggests that this high-concentration Er³⁺ center is an isolated, isoelectronic center consistent with Er³⁺ substituted on a Ga site. In contrast, a very small fraction of the Er atoms that form a variety of Er-defect/impurity complexes dominate the Er³⁺ emission spectra excited by above-gap and broad-band below-gap absorption because of their larger cross sections for both carrier capture and optical absorption.     

Origin of photoluminescence from Er3+ centers in erbium doped GaAs and Al0.4Ga0.6 As grown by MBE

Sharp erbium-related intra-4f shell luminescence from Er doped GaAs and Al_0.4Ga_0.6 As epitaxial layers grown by molecular beam epitaxy (MBE) is presented. The emission arising from the two Er³⁺ excited states,⁴I_13/2 and⁴I_11/2 are studied. We have observed, by means of heat treatment under differentambients such as As, Ga and Al over pressure, that the optically active Er³⁺ preferentially occupies a Column III lattice site or Column III related defects. The photoluminescence results of co-doping Al_0.4Ga_0.6As:Er with Si and Be by MBE is also reported for the first time. A strong single 1.54 μm spontaneous emission line is achieved by co-doping with Be (≈1×10¹⁸ cm⁻³). This improvement is a result of successfully eliminating or suppressing the other transitions without sacrificing the 1.54 μm emission intensity or linewidth.     

Excitation mechanisms of multiple Er3+ sites in Er-implanted GaN

Site-selective photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopies carried out at 6K on the ∼1540 nm ⁴I_13/2→⁴I_15/2 emissions of Er³⁺ in Er-implanted GaN have revealed the existence of four different Er³⁺ sites and associated PL spectra in this semiconductor. Three of these four sites are excited by below-gap, impurity- or defect-related absorption bands, with subsequent nonradiative energy transfer to the Er³⁺ 4f electrons; a fourth site is excited by direct Er³⁺ 4f shell absorption. PLE spectra obtained by selectively detecting Er³⁺ PL from each of the three sites pumped by broad below-gap absorption bands are compared with the PLE spectra of broad PL bands attributed to implantation damage-induced defects in the Er-implanted GaN. This comparison enables us to distinguish broad-band, below-gap optical excitation processes for Er³⁺ emission that are attributable to (1) absorption due to implantation damage-induced defects; (2) absorption due to defects or impurities characteristic of the as-grown GaN film; and (3) an Er-specific absorption band just below the band gap which may involve the formation of an Er-related isoelectronic trap. The two sites excited by impurity-or defect-related absorption bands are also strongly pumped by above-gap excitation, while the sites pumped by the Er-related trap and direct 4f shell absorption are not. This observation indicates that excitation of Er³⁺ luminescence in crystalline semiconductor hosts by either optical or electrical injection of electron-hole pairs is dominated by trap-mediated carrier capture and energy transfer processes. These trap-mediated processes may also control the thermal quenching of Er³⁺ emission in semiconductors.     

Preparation of LaOBr:Er3+ Up-conversion Luminescent Nanobelts by Electrospinning Then Bromination

Electrospun nanobelts were prepared from lanthanum oxybromide doped with trivalent erbium ions (La₂O₃:Er³⁺), then up-conversion nanobelts were successfully synthesized from these by bromination with ammonium bromide (NH₄Br) powder as bromine source and use of a double-crucible method. The products were characterized in detail by x-ray diffractometry, scanning electron microscopy, energy dispersion spectroscopy, and fluorescence spectroscopy. The results indicated the LaOBr:Er³⁺ nanobelts were tetragonal in structure with the space group P4/nmm. The width and the thickness of LaOBr:Er³⁺ nanobelts were 3.06 ± 0.42 μm and 290 nm, respectively. On excitation with a 980-nm diode laser, LaOBr:Er³⁺ the nanobelts emitted strong green and red up-conversion emission centered at 522 nm, 541 nm, and 667 nm. The green and red emission was assigned to the energy level transitions ²H_11/2 → ⁴I_15/2, ⁴S_3/2 → ⁴I_15/2, and ⁴F_9/2 → ⁴I _l5/2 of the erbium ions (Er³⁺). A mechanism of formation LaOBr:Er³⁺ up-conversion luminescence nanobelts is proposed. This bromination technique not only results in preservation of the morphology of precursor rare earth oxides, it can also be used to fabricate other pure-phase rare earth oxybromide luminescence nanomaterials at relatively low calcination temperatures.     

Effect of Yb^3＋ concentration on Er^3＋ luminescence properties of sol-gelderived silica-alumina xerogels

Er~(3 )-activated silicate glasses are recognized of tech-nological interest in several areas and,in particular ,it iswell known for their successful application in opticalamplification at the C band (1530 -1565 nm) of tele-communications[1].Inside this l…     

Effect of hydroxyl groups in erbium-doped tellurite- and bismuth-based glasses

Tellurite- and bismuth-based glasses with the composition of TeO₂–B₂O₃–GeO₂–Na₂O–Er₂O₃ and Bi₂O₃–B₂O₃–GeO₂–Na₂O–Er₂O₃, respectively, were prepared by the conventional high-temperature melt-quenching method. Infrared spectra were measured in order to investigate the effects of glass composition and bubbling oxygen treatment on the vibration absorptions of OH groups. The constants K_OH–Er for Er³⁺ in tellurite- and bismuth-based glasses, which represent the interaction strength between Er³⁺ and OH groups in the case of energy migration were calculated, and the effects of OH groups upon the fluorescence lifetimes of ⁴I_13/2 level and the emission intensities at 1.5 μm band of Er³⁺ in both glasses were investigated and compared in detail under different oxygen bubbling time.     

1.54 μm Near-infrared photoluminescent and electroluminescent properties of a new Erbium (III) organic complex

The crystal structure of Er(PM)₃(TP)₂ [PM = 1-phenyl-3-methyl-4-isobutyryl-5-pyrazolone, TP = triphenyl phosphine oxide] was reported and its photoluminescence properties were studied by UV–vis absorption, excited, and emission spectra. The Judd–ofelt theory was introduced to calculate the radiative transition rate and the radiative decay time of 3.65 ms for the ⁴I_13/2 → ⁴I_15/2 transition of Er³⁺ ion in this complex. The antenna-effect and phonon-assisted energy-transfer were introduced to discuss the intramolecular energy transfer from ligands to Er³⁺ ion. Based on this Er(III) complex as the emitter, the multilayer phosphorescent organic light emitting diode was fabricated with the structure of ITO/NPB 20 nm/Er(PM)₃(TP)₂ 50 nm/BCP 20 nm/AlQ 40 nm/LiF 1 nm/Al 120 nm, which shows the typical 1.54 μm near-infrared (NIR) emission from Er³⁺ ion with the maximum NIR irradiance of 0.21 μW/cm².     

Effect of SiO2 on the thermal stability and spectroscopic properties of Er3+-doped tellurite glasses

Er3＋-doped tellurite glass （TeO2-ZnO-Na2O） prepared using the conventional melt-quenching method is modified by introducing the SiO2, and its effects on the thermal stability of glass host and the 1.53 μm band spectroscopic properties of Er3＋ are investigated by measuring the absorption spectra, 1.53 μm band fluorescence spectra, Raman spectra and differential scanning calorimeter （DSC） curves. It is found that for Er3＋-doped tellurite glass, besides improving its thermal stability, introducing SiO2 is helpful for the further improvement of the fluorescence full width at half maximum （FWHM） and bandwidth quality factor. The results indicate that the prepared Er3＋-doped tellurite glass containing an appropriate amount of SiO2 has good prospect as a candidate of gain medium applied for 1.53 μm broadband amplifier.     

Phase relations in Cu- RO1.5- O (R < Ho,Er, Yb) and gibbs energy of formation of Cu2R2O5 (R < Ho,Er, Yb) between 1000 and 1325K

Phase relations in Cu-RO_1.5-O(R < Ho,Er,Yb) ternary systems at 1273K have been established by isothermal equilibration of samples containing different ratios of Cu:R(R < Ho,Er,Yb) in flowing air or high purity argon atmosphere for four days. The samples were then rapidly cooled to ambient temperature and the coexisting phases were identified by powder x-ray diffraction analysis. Only one ternary oxide, Cu₂R₂O₅(R < Ho,Er,Yb) was found to be stable. The chemical potential of oxygen for the coexistence of the three phase assemblage, Cu₂O + R₂O₃ + Cu₂R₂O₅(R < Ho,Er,Yb) has been measured by employing the solid-state galvanic cells,< (−) Pt, Cu₂O + Ho₂O₃+ Cu₂Ho₂O₅//CSZ//Air (Po₂< 2.12 × 10⁴ Pa), Pt (+) (−) Pt, Cu₂O + Er₂O₃+ Cu₂Er₂O//CSZ//Air (Po₂< 2.12 × 10⁴ Pa), Pt (+) (−) Pt, Cu₂O + Yb₂O₃ + Cu₂Yb₂O₅//CSZ//Air (Po₂ < 2.12 × 10⁴ Pa), Pt (+) in the temperature range of 1000 to 1325K. Combining the measured emf of the above cells with the chemical potential of oxygen at the reference electrode, using the Nernst relationship, gives for the reactions, 2Cu₂O(s) + 2Ho₂O₃(s) + O₂(g) → 2Cu₂Ho₂O₅(s) (1) 2Cu₂O(s) + 2Er₂O₃(s) + O₂(g) → 2Cu₂Er₂O₅(s) (2) and 2Cu₂O(s) + 2Yb₂O₃(s) + O₂(g) → 2Cu₂Yb₂O₅(s) (3) δΜo₂ = −219,741.3 + 145.671 T (±100) Jmol⁻¹ (4) δΜo₂ = −222,959.8 + 147.98 T(±100) Jmol⁻¹ (5) and δΜo₂ = −231,225.2 + 151.847 T(±100) Jmol⁻¹ (6) respectively. Combining the chemical potential of oxygen for the coexistence of Cu₂O + R₂O₃ + Cu₂R₂O₅(R− Ho,Er,Yb) obtained in this study with the oxygen potential for Cu₂O + CuO equilibrium gives for the reactions, 2 CuO(s) + Ho₂O₃(s) → Cu₂Ho₂O₅(s) (7) 2 CuO(s) + Er₂O₃(s) → Cu₂Er₂O₅(s) (8) and 2 CuO(s) + Yb₂O₃(s) → Cu₂Yb₂O₅(s) (9) δG‡ < 22,870.3 − 23.160 T (±100) Jmol⁻¹ (10) δG‡ < 21,261.1 − 22.002 T (±100) Jmol⁻¹ (11) and δG‡ < 17,128.4 - 20.072 T (±100) Jmol^-1 (12) It can be clearly seen that the formation of Cu₂R₂O₅R < Ho,Er,Yb) from the component oxides is endothermic. Further, Cu₂R₂O₅(R < Ho,Er,Yb) are an entropy stabilized phases. Based on the results obtained in this study, the oxygen potential diagram for Cu-R-O(R < Ho,Er,Yb) ternary system at 1273K has been composed.     

Effect of erbium fluoride doping on the photoluminescence of SiO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> films

The photoluminescence of SiO _x films deposited on c-Si wafers by the thermal evaporation of SiO in a vacuum and, for the first time, doped with ErF₃ by coevaporation is studied. It is shown that, like undoped SiO _x films, the unannealed SiO _x :ErF₃ films passivate the surface of the Si wafers and, thus, increase their edge photoluminescence intensity almost fivefold. A similar increase is observed after annealing of the doped films in air at 750°C. Doping with ErF₃ suppresses the photoluminescence of Si nanoclusters, if the films have been subjected to high-temperature annealing (at 750°C). In this case, the PL intensity of the band with a peak at ∼890 nm decreases as well. The ∼890 nm band is observed for the first time and, due to its features, is attributed to transitions in SiO _x matrix defects. The experimentally observed effect of ErF₃ doping on SiO _x film photoluminescence is interpreted. An intense photoluminescence signal from Er³⁺ ions in the nearinfrared spectral region (the ⁴ I _11/2 → ⁴ I _15/2 and ⁴ I _13/2 → ⁴ I _15/2 transitions) is observed in the SiO _x :ErF₃ films annealed in air at 750°C. This finding shows that 1.54 μm luminescent emitters, which are currently in popular demand, can be produced by a simple low-cost method.     

Pr3+‐ and Pr3+/Er3+‐Doped Selenide Glasses for Potential 1.6 μm Optical Amplifier Materials

1.6 µm emission originated from Pr³⁺: (³F₃, ³F₄) → ³H₄ transition in Pr³⁺‐ and Pr³⁺/Er³⁺‐doped selenide glasses was investigated under an optical pump of a conventional 1480 nm laser diode. The measured peak wavelength and full‐width at half‐maximum of the fluorescent emission are ~1650 nm and ~120 nm, respectively. A moderate lifetime of the thermally coupled upper manifolds of ~212 ± 10 µs together with a high stimulated emission cross‐section of ~(3 ± 1)×10^??20 cm² promises to be useful for 1.6 µm band fiber‐optic amplifiers that can be pumped with an existing high‐power 1480 nm laser diode. Codoping Er³⁺ enhances the emission intensity by way of a nonradiative Er³+: ⁴I_{13/2 →} Pr³⁺: (³F₃, ³F₄) energy transfer. The Dexter model based on the spectral overlap between donor emission and acceptor absorption describes well the energy transfer from Er³⁺ to Pr³⁺ in these glasses. Also discussed in this paper are major transmission loss mechanisms of a selenide glass optical fiber.     

A New Sol–Gel Material Doped with an Erbium Complex and Its Potential Optical‐Amplification Application

The crystal structure of a ternary Er(DBM)₃phen complex (DBM = dibenzoylmethane; phen = 1,10‐phenanthroline) and its in‐situ synthesis via a sol–gel process are reported. The infrared (IR), diffuse reflectance (DR), and fluorescence spectra of the pure complex and the Er³⁺/DBM/phen co‐doped luminescent hybrid gel, formed via an in‐situ method (ErDP gel), have been investigated. The results reveal that the erbium complex is successfully synthesized in situ in the ErDP gel. Excitation at the maximum absorption wavelength of the ligands resulted in the typical near‐IR luminescence (centered at around 1.54 μm) resulting from the ⁴I_13/2 → ⁴I_15/2 transition of the Er³⁺ ion, which contributes to the efficient energy transfer from the ligands to the Er³⁺ ion in both the Er(DBM)₃phen complex and the ErDP gel (an antenna effect). The full width at half maximum (FWHM) centered at 1541 nm in the emission spectrum of the ErDP gel is 72 nm, which has potential for optical‐amplification applications. Further theoretical analysis on the Er³⁺ ion in the ErDP gel shows that it appears to be a promising candidate for tunable lasers and planar optical amplifiers.     

NMOSFET characteristics on a double hetero-epitaxial Si/γ-Al2O3/Si structure fabricated by a new MBE growth method

A new MBE growth method for the fabrication of a high-quality double hetero-epitaxial Si/γ-Al₂O₃/Si structure was recently developed. In the present work, characteristics of NMOSFETs fabricated on the Si/γ-Al₂O₃/Si structure were investigated, and compared with those on a Si/MgAl₂O₄/Si structure. A γ-Al₂O₃ layer was created from a MgAl₂O₄ layer by reaction with Si beams as follows: MgAl₂O₄ + Si → γ-Al₂O₃ + SiO ↑ + Mg ↑. The MBE growth of Si on the effectively restructured γ-Al₂O₃ layer was then performed at a substrate temperature of 700° C, 150° C lower than for the MBE growth of Si on a MgAl₂O₄/Si substrate. The electron field effect mobility and leakage current between source and drain for the NMOSFETs fabricated on Si/γ-Al₂O₃/Si structures were 660 cm²/V · s and 2.8 pA/μm respectively, and exhibited a higher level of performance than those on a Si/MgAl₂O₄/Si structure. In the Si/MgAl₂O₄/Si, SIMS measurements confirmed that autodoped Al and Mg atoms near the interface between the Si epi-layer and MgAl₂O₄/Si substrate diffused anomalously and accumulated at the surface during device fabrication processes. These autodoped Al and Mg atoms acted as ionized impurities during test operation. Suppression of autodoping from insulator layers during the MBE growth of Si was thus deemed essential to the improvement of NMOSFET characteristics. In the Si/γ-Al₂O₃/Si structure, autodoped atoms were scarcely detectable. It was therefore concluded that the Si/γ-Al₂O₃/Si structure under study was very promising for SOI device applications.     

Er3+–Tm3+ co-doped tellurite fibers for broadband optical fiber amplifier around 1550 nm band

Tellurite fibers with 7500 ppm Er³⁺ concentration and diverse 2500–15,000 ppm Tm³⁺ concentrations were manufactured, and their amplified spontaneous emission (ASE) intensities 1550 nm band around were obtained for 980 and 790 nm pump laser. Maxima 187 nm bandwidth at −3 dB points using Er³⁺–Tm³⁺ co-doped tellurite optical fibers pumping at 790 nm was obtained, and energy transfer (ET) process between ⁴I_13/2 Er³⁺ and ³F₄ Tm³⁺ levels related with the amplifier quantum efficiency was studied from experimental and calculated lifetime.     

Spectral properties and energy transfer in Er3+/Yb3+ co-doped LiYF4 crystal

Laser crystals of LiYF4 (LYF) singly doped with Er3+ in 2.0% and co-doped with Er3+/Yb3+ in about 2.0%/1.0% molar fraction in the raw composition are grown by a vertical Bridgman method. X-ray diffraction (XRD), absorption spectra, fluorescence spectra and decay curves are measured to investigate the structural and luminescent properties of the crystals. Compared with the Er3+ singly doped sample, obviously enhanced emission at 1.5 μm wavelength and green and red up-conversion emissions from Er3+/Yb3+ co-doped crystal are observed under the excitation of 980 nm laser diode. Meanwhile, the emission at 2.7 μm wavelength from Er3+ singly doped crystal is reduced. The fluorescence decay time ranging from 18.60 ms for Er3+ singly doped crystal to 23.01 ms for Er3+/Yb3+ co-doped crystal depends on the ionic concentration. The luminescent mechanisms for the Er3+/Yb3+ co-doped crystals are analyzed, and the possible energy transfer processes from Yb3+ to Er3+ are proposed.     

Composition-induced valence variation of europium and the photoluminescence properties for Eu2+ doped borophosphate luminous glass in air

A simultaneous blue-light and red-light emitting glass of SrO-B2O3-P2O5 doped with Eu2O3 is prepared in air, and then heat-treated without any reductive reagent. A transition combination is found to consist of a band emission peaked around 430 nm and a series of line emission from 593 nm to 611 nm, corresponding to the typical 4f65d→ 4f7 transition of Eu2+ and 5D0 → 7FJ (J = 0, 1, 2, 3, 4) transitions of Eu3+, respectively. Some unidentified crystals such as Sr (PO3)2 and SrB2O4 as hosts for Eu2...