Anomalous luminescence properties and cytotoxicity assessment of Sr₃(PO₄)₂ co-doped with Eu^2+/3+ ions for luminescence temperature sensing

Abstract

Strontium phosphate (Sr3(PO4)2) powders co-doped with Eu3+ and Eu2+ optically active ions were obtained by modified Pechini’s method and heat-treated at 900°, 1000° and 1100°C in air atmosphere. Structural and...

Tetrahedrally coordinated rigid crystal structure enables partial self-reduction of mixed-valence europium for optical thermometric application

“…The self-reduction of Eu in the CaBPO 5 matrix can be explained by the charge compensation model. 33,65 Two Eu 3+ ions heterovalently doped at two Ca 2+ sites create a charge negative vacancy, V′′ Ca (Kröger–Vink notation), near the Eu 3+ ion to maintain charge neutrality. The negative charges in the V′′ Ca vacancy will thermally transmit to the Eu 3+ ion, thus reducing the Eu 3+ to Eu 2+ as suggested by the following expressions: 42,48,66 …”

“…[29][30][31] According to the configuration diagram, there is no cross point between the ground 4f 6 and excited 4f 6 parabolas due to the negligible ion-lattice interactions for Eu 3+ , making the Eu 3+ emission thermal quenching via multiphonon relaxation inaccessible. 32,33 However, the 4f 6 5d 1 electrons can strongly interact with lattice vibrations or host conduction bands on account of the outer extended Eu 2+ 4f 6 5d 1 orbits, which usually results in Eu 2+ emission being highly sensitive to temperature fluctuation. [34][35][36] Therefore, incorporating mix-valent Eu 2+ /Eu 3+ into a host, in principle, can be utilized for the of high-performance temperature sensors by employing the Eu 2+ /Eu 3+ FIR as a temperature probe.…”

Co-Doping Effect of Mn2+ and Eu3+ on Luminescence in Strontiowhitlockite Phosphors

“…The replacement of Ca 2+ with Sr 2+ ions leads to an increase in the photoluminescence properties [ 16 ] or their modification [ 17 , 18 ] due to the formation of more distorted luminescence center environments. It is worth noting that pure Sr 3 (PO 4 ) 2 differs from the β-Ca 3 (PO 4 ) 2 structure [ 19 ] and is known as a mineral palmierite family member. Furthermore, a comprehensive substitution of Ca 2+ → Sr 2+ was investigated in detail in [ 20 ].…”

“…It is worth noting that pure Sr 3 (PO 4 ) 2 differs from the β-Ca 3 (PO 4 ) 2 structure [19] and is known as a mineral palmierite family member. Furthermore, a comprehensive substitution of Ca 2+ → Sr 2+ was investigated in detail in [20].…”