Improved thermal conductivity and tailored phonon dynamics in hexagonal prism-like ZnO:Er³⁺ upconverting phosphor

Abstract Er 3+ ions doped ZnO phosphors have been synthesized by using the chemical co-precipitation method. X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), Inductively Coupled Plasma Mass Spectrometry (ICP-MS), UV–Visible, and Raman spectroscopy characterizations were performed for the developed phosphor. Upconversion emission spectra under 980 nm laser diode excitation show detectable Er 3+ ion transitions in the visible colour region. The introduction of the Er 3+ in the ZnO matrix exhibits two strong new Raman modes at 637 cm −1 due to 2(E 2H -E 2L ) and 830 cm −1 due to A 1 (TO) + E 2L , originating via tailored phonon dynamics. An unusual linewidth narrowing and blue shift of the characteristic Raman band of the wurtzite structure corresponding to the E 2H Raman mode of the ZnO: Er 3+ phosphor has been observed. An enhanced phonon lifetime of about 1.56 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>12</mml:mn> </mml:mrow> </mml:msup> </mml:math> s was calculated for the E 2H Raman mode. Moreover, the thermal conductivity measurement shows a noticeable increment in the ZnO: Er 3+ (0.072 W·m −1 ·K −1 ) as compared to the ZnO (0.067 W·m −1 ·K −1 ) phosphor due to the reduced electron–phonon coupling. The synthesized ZnO: Er 3+ phosphor may be used for upconverting and thermoelectric material development.