Novel Smart Materials With High Curie Temperatures: Eu<sub>1.90</Sub> Dy<sub>0.10</Sub>ge<sub>2< , Eu<sub>1.90</Sub> La<sub>0.10</Sub>ge<sub>2< and Eu<sub>1.90</Sub> Ho<sub>0.10</Sub> Ge<sub>2</Sub> O<sub>7</Sub>

Abstract

The Eu-1.90 Dy0.10Ge2O7 , Eu-1.90 La0.10Ge2O7 and Eu-1.90 Ho-0.10 Ge-2 O-7 powder were obtained through a solid-state reaction method via multistep firing of stoichiometric ratios of Eu2O3, GeO2, Dy2O3, La2O3 and Ho2O3 in open atmosphere at temperatures from 800 to 1150 degrees C. The thermal behaviour, phase formation, SEM/EDX analysis, photoluminescence properties, Curie tempereture, dielectric and piezoelectric properties of the samples were investigated by TG/DTA, XRD, SEM, PL, TG/DTA, LCR-meter and d33-meter, respectively. The germenates having triclinic crystal system have D-5(0)-> F-7(4), D-5(0)-> F-7(3), D-5(0 )-> F-7(2), 5D0 -> 7F1 transitions of Eu(3+)ions. Also, the photoluminescent germenates show electrical properties and the piezoelectric charge constant of germenates showed Eu1.90Dy0.10Ge2O7>Eu1.90Dy0.10Ge2O7 >Eu1.90La0.10Ge2O7 trend. The Curie temperature of Eu1.90Dy0.10Ge2O7, Eu1.90Dy0.10Ge2O7 and Eu1.90Dy0.10Ge2O7 are 825, 844 and 838 degrees C, respectively. Compared to commonly used piezoelectric materials, Eu1.90Dy0.10Ge2O7, Eu1.90Dy0.10Ge2O7 and Eu1.90Dy0.10Ge2O7 materials with very high Curie temperatures were obtained with photoluminescent properties.