The investigation of the photoluminescent and piezoelectric effect of Eu3+ doped Y2Ti2O7 and Sm2Ti2O7 host crystals

Y1.98Eu0.02Ti2O7 and Sm1.98Eu0.02Ti2O7 with a cubic pyrochlore-type structure were synthesized from stoichiometric mixtures of the constituent oxides using a solid solution reaction method at 1400 °C in an open atmosphere. Their crystal structures and lattice constants were determined by X-ray powder diffractometry. To determine the thermal behaviour of the mixtures of the starting materials, differential thermal analysis (DTA) and thermogravimetric (TG) analysis were used. The surface morphology and EDX analysis of the samples were investigated using a scanning electron microscope (SEM). The photoluminescence properties were measured and the red emission was observed from Y1.98Eu0.02Ti2O7 and Sm1.98Eu0.02Ti2O7 phosphors. Both materials show the typical emission bands of Eu3+ ions. The emission spectra of the Y1.98Eu0.02Ti2O7 and Sm1.98Eu0.02Ti2O7 phosphors consist of several intense peaks in the red spectral range, which correspond to the characteristic transitions of Eu3+ from 5D0 to 7FJ (J = 2, 3, 4). When Eu3+ ions are doped to Sm2Ti2O7 host crystal, the life time prolongs 800 times compared with Y2Ti2O7 host crystal and the luminescent intensity was remarkably improved by the incorporation of Eu3+ and Y2Ti2O7 host microcrystal. Also, the dielectric constant, loss tangent, piezoelectric charge constant and Curie temperature were investigated by LCR-meter, d33-m and TG/DTA, respectively. Y1.98Eu0.02Ti2O7 has the bigger piezoelectric charge constant and Sm1.98Eu0.02Ti2O7 (1561 °C) has a higher Curie temperature than Y1.98Eu0.02Ti2O7 (1449 °C).