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Distinct types of luminescence that are activated by various stimuli in a single material offer exciting developmental opportunities for functional materials. A versatile sensing platform that exhibits photoluminescence (PL), persistent luminescence (PersL), and mechanoluminescence (ML) is introduced, which enables the sensitive detection of temperature, pressure, and force/stress. The developed Sr2MgSi2O7:Eu2+/Dy3+ material exhibits a linear relationship between ML intensity and force and can be used as an ML stress sensor. Additionally, the bandwidth of the PL emission band and the PL lifetime of this material are remarkably sensitive to temperature, with values of ≈0.05 nm K−1 and 1.29%/K, respectively. This study demonstrates PersL pressure sensing for the first time, using long‐lasting (seconds) lifetime as a manometric parameter. The developed material functions as an exceptionally sensitive triple‐mode visual pressure sensor; specifically, it exhibits: i) a sensitivity of ≈−297.4 cm GPa−1 (8.11 nm GPa−1) in bandshift mode, ii) a sensitivity of ≈272.7 cm−1/GPa (14.8 nm GPa−1) in bandwidth mode, and iii) a sensitivity of 42%GPa−1 in PL‐lifetime mode, which is the highest value reported to date. Notably, anti‐counterfeiting, night‐vision safety‐sign, 8‐bit optical‐coding, and QR‐code applications that exhibit intense PersL are demonstrated by 3D‐printing the studied material in combination with a polymer. [ABSTRACT FROM AUTHOR]

A comprehensive photoluminescence and mechanoluminescence analysis of a ZnS:Mn2+ nano-phosphor with a zinc blende structure is presented. The sample containing quantum dot-sized nanocrystallites was synthesized by the chemical precipitation method and shows excellent orange luminescence at ambient conditions related to the 4T1 → 6A1 transition. The sample shows stable and identical luminescence behavior under both UV and X-ray excitation at ambient conditions and also exhibits excellent self-powered mechanoluminescence properties. The pressure and temperature-induced luminescence mechanism of the phosphor is also established. The shift of the 4T1 → 6A1 luminescence band of Mn2+ with both pressure and temperature and the luminescence mechanism is explained via the d5 Tanabe Sugano diagram. The broad luminescence band of the 4T1 → 6A1 transition shifts from the visible to near-infrared range at a rate of −35.8 meV GPa−1 with the increase of the pressure and it is subsequently quenched completely at a pressure of 16.41 GPa due to a reversible phase transition from zinc blende (F4¯3m) to rocksalt (Fm3¯m) phase. The high-pressure and temperature-dependent decay kinetics measurements of the sample luminescence are also reported. [ABSTRACT FROM AUTHOR]

α-SrSi2O2N2 is one of the recently studied oxonitridosilicates applicable in optoelectronics, in particular in white LEDs. Its elastic properties remain unknown. A survey of literature shows that, up to now, nine oxonitridosilicate materials have been identified. For most of these compounds, doped with rare earths and manganese, a luminescence has been reported at a wavelength characteristic for the given material; all together cover a broad spectral range. The present study focuses on the elastic properties of one of these oxonitridosilicates, the Eu-doped triclinic α-SrSi2O2N2. High-pressure powder diffraction experiments are used in order to experimentally determine, for the first time, the equation of state of this compound. The in situ experiment was performed for pressures ranging up to 9.65 GPa, for Eu-doped α-SrSi2O2N2 sample mounted in a diamond anvil cell ascertaining the hydrostatic compression conditions. The obtained experimental variation of volume of the triclinic unit cell of α-SrSi2O2N2:Eu with rising pressure served for determination of the Birch-Murnaghan equation of state. The determined above quoted bulk modulus is 103(5) GPa, its first derivative is 4.5(1.1). The above quoted bulk modulus value is found to be comparable to that of earlier reported oxynitrides of different composition. [ABSTRACT FROM AUTHOR]

Highlights: [•] Luminescence properties of β-Ca2SiO4 doped with Eu2+ and Eu3+ are studied. [•] Short distance compensation model of the Eu3+ replacing Ca2+ is discussed. [•] The existence of stable Eu2+ and Eu3+ was discussed in relation to the Fermi level. [ABSTRACT FROM AUTHOR]

Abstract: Eu2+ doped Sr2SiO4 phosphors were synthesized by solid state synthesis technique. The purity and crystal structure of the materials was studied with the X-ray powder diffraction. Depending on the synthesis method the materials contain one (α′) or two (α′+β) crystal phases. Luminescence properties were studied in UV–Vis range at ambient and high hydrostatic pressure. Two broad emission bands in the yellow–orange and blue–green region were attributed to the 9-fold coordinated and 10-fold coordinated Eu2+, respectively. We found that increasing pressure causes a red shift of the yellow–orange emission. This is typical pressure dependence related to 4f65d1 → 4f7 transition in Eu2+ observed also in other materials. In the case of blue–green band, when pressure increases from ambient to 50kbar, the emission band shifts strongly to higher energy, and for pressure higher than 50kbar does not depend on pressure. This effect was considered in framework of crystal field model. We presumed that electrostatic field in a 10-fold coordinated site is a superposition of crystal field of four ligands that belong to tetrahedral coordination and six ligands belonging to octahedral coordination. We discussed untypical pressure dependence of the blue–green emission band as a result of pressure influence on the lower excited state in Eu2+, i.e. 4f65d1(e) at octahedral and 4f65d1(t) at tetrahedral coordination. [Copyright &y& Elsevier]

α-SrSi2O2N2 is one of the recently studied oxonitridosilicates applicable in optoelectronics, in particular in white LEDs. Its elastic properties remain unknown. A survey of literature shows that, up to now, nine oxonitridosilicate materials have been identified. For most of these compounds, doped with rare earths and manganese, a luminescence has been reported at a wavelength characteristic for the given material; all together cover a broad spectral range. The present study focuses on the elastic properties of one of these oxonitridosilicates, the Eu-doped triclinic α-SrSi2O2N2. High-pressure powder diffraction experiments are used in order to experimentally determine, for the first time, the equation of state of this compound. The in situ experiment was performed for pressures ranging up to 9.65 GPa, for Eu-doped α-SrSi2O2N2 sample mounted in a diamond anvil cell ascertaining the hydrostatic compression conditions. The obtained experimental variation of volume of the triclinic unit cell of α-SrSi2O2N2:Eu with rising pressure served for determination of the Birch-Murnaghan equation of state. The determined above quoted bulk modulus is 103(5) GPa, its first derivative is 4.5(1.1). The above quoted bulk modulus value is found to be comparable to that of earlier reported oxynitrides of different composition. [ABSTRACT FROM AUTHOR]

A 0.25% iron (Fe 3+ )-doped LiGaO 2 phosphor was synthesized by a high-temperature solid-state reaction method. The phosphor was characterized utilizing X-ray diffraction (XRD), scanning electron microscopy (SEM), high-pressure photoluminescence, and photoluminescence decay measurement techniques using diamond anvil cells (DACs). The powder X-ray analysis shows that the phosphor is a β polymorph of LiGaO 2 with an orthorhombic crystallographic structure at room temperature. The SEM result also confirms the presence of well-dispersed micro-rod-like structures throughout the sample. The photoluminescence studies in the near-infrared (NIR) range were performed at ambient, low-temperature, and high-pressure conditions. The synthesized phosphor exhibits a photoluminescence band around 746 nm related to the 4 T 1 → 6 A 1 transition with a 28% quantum efficiency at ambient conditions, which shifts toward longer wavelengths with the increase of pressure. The excitation spectra of Fe 3+ are very well fitted with the Tanabe-Sugano crystal-field theory. The phosphor luminescence decays with a millisecond lifetime. The high-pressure application transforms the β polymorph of LiGaO 2 into a trigonal α structure at the pressure of about 3 GPa. Further increase of pressure quenches the Fe 3+ luminescence due to the amorphization process of the material. The prepared phosphor exhibits also mechanoluminescence properties in the NIR spectral region.