SYNTHESIS AND CHARACTERIZATION OF CA2+-SUBSTITUTED SELF- ACTIVATED PHOTOLUMINESCENCE MATERIAL OF NA2TISIO5 BY SOLID STATE METHOD

• Main Author: Dian Ruhimat, Dzaky
• Format: Final Project
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/64427
• Institution: Institut Teknologi Bandung

Energy crisis which occurs in the world gives a warning for everyone to conserve as much energy as possible. Lighting is one of the high-energy consuming applications. Light emitting diode (LED) is a promising lighting device due to high energy saving and environment- friendly properties. Rare-earth doped phosphor materials are the most common studied materials as suitable LED device candidates. However, due to their expensive price, rare-earth elements might produce highly-priced LEDs as well. Na2TiSiO5 (NTSO) could be one solution to avoid rare-earth doped photoluminescence (PL) material usage. Self-activated property, which is the ability to emit light without any additional elements, becomes main advantage of NTSO. Compared to NTSO, the analogous compound of CaTiSiO5 (CTSO) is known as non- self-activated PL material. Apart from the difference in alkaline earth cations, the main difference between both compounds is the existence of TiO5 and TiO6 units which coexist in NTSO crystal structure, whereas only TiO6 octahedral unit exists in CTSO. Those differences motivate author to study luminescence properties of Ca2+-substituted NTSO. This research aims to determine the effects of Ca2+ to crystal structure and optical properties of NTSO. Na2(1-x)CaxTiSiO5 (x = 0; 0.01; 0.05; 0.10; 0.15; 0.20; 0.25) solids were sucessfully synthesized by solid state method, according to X-ray diffraction characterization and Rietveld refinement. Optical properties of Na2(1-x)CaxTiSiO5 were analyzed using UV Diffuse Reflectance Spectra (DRS) and photoluminescence spectra. The confirmation of Ca2+ substitution was obtained from Na2(1-x)CaxTiSiO5 diffraction patterns, which shift to higher 2? values. There is also a new peak observed at 2? ? 33º, where the intensity increases as Ca2+ concentration increases. This peak is presumed to be originated from CaTiO3 impurity. However, the conjecture is denied from charge-compensated Na2-yCayTiSiO5 diffraction pattern. Thus, that peak is presumed originating from symmetry reduction of NTSO structure. UV-DRS data for NTSO shows absorption peaks at 282 and 373.5 nm. Increasing Ca2+ concentration decreases absorption intensity at 373.5 nm and produces new absorption peak at 314.81 nm. PL spectra of Na2(1-x)CaxTiSiO5 shows white emission in a range of 350-650 nm. Maximum intensity is achieved when x = 0.10. These experimental facts could provide indications to comprehend structural, energy states changes, and electronic transition types in Na2(1-x)CaxTiSiO5.