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A series of Sm3 +-doped 0. 96Na0 .5Bi0.5TiO3-0.04CaTiO3 (NBT-0. 04CT:xSm3+, 0. 002 ≤x ≤ 0. 020) lead-free piezoelectric ceramics were prepared by a conventional solid-state reaction method. The phase structures of the samples were characterized by X-ray diffractometry, and all the samples show a single perovskite structure. The photoluminescence properties of the samples were measured by fluorescence spectrophotometer, and the samples show the strongest excitation peak at 479 nm, which matches well with the blue LED chip used in the white LED synthesis. The dominant emission peak is located at 597 nm (4G5/2→ 6 H7/9), presenting strong orange-red luminescence. NBT-0. 04CT:0. 010Sm3+ ceramics shows optimal luminescence performances among the Sm3 +-doped NBT-0. 04CT ceramics, and superior thermal stability of its luminous properties is achieved in the temperature range from 278 K to 473 K. The results indicate that NBT-0. 04CTxSm3 + ceramics have promising applications in white LED. [ABSTRACT FROM AUTHOR]

Sm3+-Modified (1 − x)Na0.5Bi0.5TiO3-xCaTiO3 (NBT-xCT:Sm3+) piezo-luminescent ceramic materials were synthesized to investigate the influence of CaTiO3 (CT) concentration on their photoluminescence and electrical performance. Under 480 nm irradiation, the NBT-xCT:Sm3+ samples exhibit prominent orange-red emission, with a prime emission peak centered at 597 nm. A moderate amount of CT doping in the Sm3+-modified NBT ceramics boosts both their photoluminescence and piezoelectric properties significantly, with NBT-0.04CT:Sm3+ showing the optimal performance. Furthermore, outstanding luminescence thermal stability over a temperature range of 293–473 K and superior water resistance behavior are achieved in the NBT-0.04CT:Sm3+ ceramic. These results indicate that NBT-xCT:Sm3+ piezo-luminescent ceramics show great potential applications in white LEDs, as well as novel optical-electronic multifunctional devices. [ABSTRACT FROM AUTHOR]

Luminescent piezoelectric materials promise a stratagem for controlling the optical process by electric field, which would benefit for future optoelectronic devices. Here, Er3+ doped (Ba 0.85 Ca 0.15) (Zr 0.1 Ti 0.9)O 3 (BCZT: Er3+) piezoelectric ceramics are prepared to demonstrate the proof of concept. In addition to excellent intrinsic piezoelectricity and ferroelectricity, BCZT: Er3+ ceramics exhibit simultaneously strong green upconversion emissions under excitation of 980 nm. Remarkable photoluminescence (PL) quenching phenomenon as well as significant changes on relative intensities of stark lines are observed under external poling electric field. Furthermore, field dependent piezoelectric constant d 33 and photoluminescence quenching ratio show similar variation trend and finally saturate for E > 3.5 kV/mm, which provides a noncontact strategy to monitor the piezoelectric constant d 33. The PL quenching triggered by electric field in BCZT: Er3+ ceramics is ascribed to the decreased asymmetry originating from field-induced structural transformation from a significant fraction of the tetragonal phase to rhombohedral phase. Our work would be helpful for expanding the scope of luminescent piezoelectric materials and promising future optoelectronic and optical devices with cross-coupled physical properties. • Ferroelectricity and upconversion emissions coexist in BCZT: Er3+. • Electric field can modulate photoluminescence and relative intensity of stark lines. • A noncontact strategy to monitor the piezoelectric constant is proposed. • The mechanism of electric field-photoluminescence coupling is analyzed. [ABSTRACT FROM AUTHOR]

Abstract A series of orange-red emitting Sm3+ activated Ba 0.85 Ca 0.15 Ti 0.90 Zr 0.10 O 3 (BCZT: x Sm3+, x = 0.001–0.007) are synthesized by a conventional solid-state reaction method. The Sm3+ ions composition dependent photoluminescence properties are systematically investigated. Under the excitation of a 407 nm near-ultraviolet light, the ceramics exhibit strong characteristic emission of Sm3+ ions with dominant orange-red emission peak at around 595 nm, which is ascribed to the transition of 4G 5/2 → 6H 7/2. The BCZT: 0.004Sm3+ ceramic displays the optimal emission among these Sm3+-doped BCZT solid solutions. Moreover, the photoluminescence intensity exhibits extremely sensitive to temperature, suggesting that BCZT: 0.004Sm3+ could be applicable for temperature sensing. A maximum relative sensitivity of 1.89% K−1 at 453 K is obtained. Furthermore, the existence of ferroelectricity in the BCZT host combined with Sm3+ activated photoluminescence properties could be useful for developing optical-electro multifunctional materials and devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • A moderate amount of Dy3+ doping can enhance the ferroelectricity of the NBT host. • The NBT: x Dy3+ specimens exhibit intense prominent orange-yellow emission with optimal performance for x = 0.012. • The NBT: 0.012Dy3+ ceramic could be applied to optical temperature sensing. A series of Dy3+ doped Na 0.5 Bi 0.5 TiO 3 (NBT: x Dy3+, x = 0.003–0.018) lead-free ferroelectric ceramics were successfully prepared by a solid-state reaction method. The Dy3+ ions composition dependent photoluminescence properties were systematically studied. All the samples display intense characteristic emission of Dy3+ under an excitation wavelength of 454 nm, which are attributed to the transitions of 4F 9/2 → 6H J /2 (J = 13, 11 and 9). All the samples show strong orange-yellow emission, which could be applied to warm white light hopefully. When the content of Dy3+ is equal to 0.012, the ceramic has the optimal luminous performance. Remarkable thermal quenching of the luminous intensity ceramic occurs as the temperature is higher than initial temperature 293 K. Furthermore, Dy3+ activated photoluminescence performance combined with the presence of ferroelectricity in the NBT host can be applied to developing non-contact optical temperature sensitive materials and other future novel optoelectronic devices. [ABSTRACT FROM AUTHOR]

Luminescent ions doped lead free ferroelectric ceramics are the potential candidates to the widespread application of optoelectronic devices due to the coupling between their unique photoluminescence and inherent ferroelectric performance. In this work, the tunable photoluminescence response is successfully achieved in (1- x)Na 0·5 Bi 0·5 TiO 3 - x CaTiO 3 : Eu3+ (NBT- x CT: Eu3+, x =0.07, 0.1) via electric field poling. It is found that the enhancement of photoluminescence intensity became apparent for polarized NBT-0.07CT: Eu3+, wherein x =0.07 is near the morphotropic phase boundary region. However, for NBT-0.1CT: Eu3+ ceramic with a morphotropic phase boundary, the variation trend of the emission intensity after electric field poling is opposite. These results are ascribed to the lattice distortion and phase transition induced by an external field poling, which originates from ferroelectric and structural instability near and in the morphotropic phase boundary of NBT- x CT: Eu3+ (x =0.07, 0.1) ceramics. • The NBT- x CT: Eu3+ specimens exhibit strong prominent red emission. • The lattice distortion and phase transition are induced by an external field poling. • Electric-field-induced photoluminescence modulation is successfully achieved. • NBT-0.07CT: Eu3+ possesses more superior performance than NBT-0.1CT: Eu3+. [ABSTRACT FROM AUTHOR]

Luminescent temperature sensors based on photoluminescent materials have received considerable attention for their advantages of quick and noninvasive measurement. In this paper, a series of Tb3+, Eu3+ single-doped and co-doped Ca 2 Al 2 SiO 7 (CAS) phosphors were synthesized by sol-gel method. The phase purity, surface morphology, energy transfer, luminescence characteristics and temperature sensing properties of Tb3+, Eu3+ doped CAS phosphors have been studied carefully. Due to the energy transfer of Tb3+→Eu3+, CAS: Tb3+, Eu3+ phosphors demonstrate tunable luminescence under 238 nm excitation, in which the luminescence color gradually changes from purple-red to cool white, and then to warm white by continuously increasing the concentration of Tb3+ ions. The elongation of the fluorescence lifetime of Eu3+ with increasing Tb3+ ions content further confirms the energy transfer of Tb3+→Eu3+. The thermal behavior of CAS: Tb3+, Eu3+ phosphors shows enhanced luminescence intensity for 404 nm emission while suppressed luminescence intensity for 616 nm emissions with raising temperature, implying its potential in optical temperature sensing. Therefore, the temperature sensing performance is evaluated by using the fluorescence intensity ratio (I 404 nm /I 616 nm) in CAS: Tb3+, Eu3+ phosphors, showing a maximum relative sensitivity of 1.17%K−1 at 443 K. These results indicate that CAS: Tb3+, Eu3+ phosphors are promising candidates for tunable luminescence and non-contact temperature sensing. [ABSTRACT FROM AUTHOR]

A series of Sm3+ doped 0.92(Na 0.5 Bi 0.5)TiO 3 -0.08(Ba 0.90 Ca 0.10)(Ti 0.92 Sn 0.08)O 3 (NBT-8BCTS: x Sm3+, x = 0–0.025) lead-free piezoelectric ceramics are fabricated via a conventional solid-state reaction method, and their phase structure, photoluminescence properties and temperature dependent of luminescence spectra are studied in detail. The emission spectra with dominant orange-red emission consist of four emission peaks at 542 nm, 598 nm, 644 nm and 709 nm, which are ascribed to the 4G 5/2 → 6H J/2 (J = 5, 7, 9, 11) transition of Sm3+ ions, respectively. Furthermore, the optical temperature sensing properties of the NBT-8BCTS: 0.01Sm3+ ceramic in the temperature range between 313 K and 533 K are analyzed with a maximum relative sensitivity 1.29%K−1 at T = 463 K. Besides, the phosphors exhibit excellent stable temperature sensing performance under repeated heat-cooling cycles. These results suggest that the Sm3+ doped NBT-8BCTS ceramics may have potential applications in multifunctional sensing devices by integrating its optical temperature sensing and intrinsic ferroelectric property. [Display omitted] • Ferroelectricity and photoluminescence emissions coexist in NBT-BCTS: x Sm3+. • A maximum relative sensitivity of 1.29% K−1 at 463 K is obtained. • Sm doped NBT-BCTS ceramics have potential for developing multifunctional optical-electric devices. [ABSTRACT FROM AUTHOR]

Eu3+ singly-doped Ba 2 La 6 Y 2 (SiO 4) 6 O 2 phosphors with hexagonal structure have been synthesized by the high-temperature solid-state reaction method. The crystal structure of the samples was analyzed. To investigate the site occupation of Eu3+ in Ba 2 La 6 Y 2 (SiO 4) 6 O 2 , the photoluminescence behavior of the phosphor was studied systematically. The emission spectra under specific wavelength excitations and the excitation spectra by monitoring emissions at 5D 0 →7F 0 transition wavelengths indicated that Eu3+ ions have entered two distinct sites in the compound. According to the concentration-dependent photoluminescence properties, the preferential site occupation was illustrated. In addition, the temperature-dependent PL measurement results revealed the high thermal stability of the sample and its application potential as a noninvasive optical thermometer. This work may help to provide an alternative approach to study the site occupation of Eu3+ ions in other functional materials. • A new Eu3+-activated Ba 2 La 6 Y 2 (SiO 4) 6 O 2 phosphor was synthesized via solid-state method. • The site occupation of Eu3+ was investigated according to the photoluminescence properties. • The phosphor has a high thermal stability. • The synthesized sample could have application potential as a noninvasive optical thermometer. [ABSTRACT FROM AUTHOR]

A novel broadband (SrCa) 2 La(PO 4) 3 O: Eu2+ phosphor was successfully synthesized by the conventional high-temperature solid-state reaction. The samples are of phase purity demonstrated by XRD analysis. The photoluminescence properties of the (SrCa) 2 La(PO 4) 3 O: Eu2+ phosphor were investigated systematically. Under the excitation of 365 nm near-ultraviolet light, the phosphors exhibit absorption in the ultraviolet–visible spectral region of 280–420 nm and show an intense asymmetric broadband blue emission peaking at around 460 nm. The different crystallographic sites of Eu2+ in (SrCa) 2 La(PO 4) 3 O: Eu2+ phosphors have been verified via the photoluminescence properties. The concentration quenching mechanism, decay property, and thermal stability of the phosphor have been discussed in detail. The investigation results indicate that the as-prepared (SrCa) 2 La(PO 4) 3 O: Eu2+ phosphor will have application potential in near-ultraviolet pumped white light-emitting diodes. • A newly found compound (SrCa) 2 La(PO 4) 3 O was synthesized. • The emitting color of the (SrCa) 2 La(PO 4) 3 O: Eu2+ phosphor varies with Eu2+ concentration. • The synthesized sample could have application potential in NUV pumped wLEDs. [ABSTRACT FROM AUTHOR]

A series of Sr 3 La 2 (PO 4) 2 (SiO 4)O: Eu2+ phosphors were synthesized by conventional high-temperature solid-state reaction. The phase formation was confirmed by XRD analysis. The photoluminescence properties of Sr 3 La 2 (PO 4) 2 (SiO 4)O: Eu2+ phosphors were investigated systematically. The phosphors exhibit absorption in the ultraviolet–visible spectral region of 280–420 ​nm and show an intense asymmetric broadband blue emission peaking at 454 ​nm under the excitation at 365 ​nm. The concentration quenching mechanism, decay property, and thermal stability have been discussed in detail. The investigation results indicate that Sr 3 La 2 (PO 4) 2 (SiO 4)O: Eu2+ will have applications as the blue component in tricolor near-ultraviolet pumped white light-emitting diodes. The Sr 3 La 2 (PO 4) 2 (SiO 4)O: Eu2+ phosphor was reported, which shows the potential application as a blue component in tricolor n-UV pumped wLEDs. Image 1 [ABSTRACT FROM AUTHOR]