Crystal field Analysis of emission wavelength of Eu-doped phosphers by means of electron spin resonance

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K05090
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 26020:Inorganic materials and properties-related
• Research Institution: Kagawa University
• Principal Investigator: Hayato Miyagawa 香川大学, 創造工学部, 教授 (00380197)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: Eu賦活蛍光体 / Sr3MgSi2O8 / CaAlSiN3 / Rietveld解析 / 擬正四面体拘束

Outline of Final Research Achievements

The effect of the coordination structure around the Eu ions on the emission wavelength was investigated by combining Rietveld analysis of X-ray diffraction and the evaluation of the crystal field by ESR (electron spin resonance) for CaAlSiN3:Eu (CASN), which emits red light, and Sr3MgSi2O8:Eu (SMS), which emits blue light, as eu-activated phosphors. We analyzed the atomic coordinates with high accuracy by introducing a two-phase fit in an SMS sample during low-temperature firing and a quasi-tetrahedral constraint condition fitting for the relationship between the emission wavelength of CASN and the Eu concentration. In addition, photoelectron spectroscopy and magnetization susceptibility were measured, and data to be reinforced were obtained. The shorter the mean distance between the Eu-O bonds, the more red shift occurred, and the correlation between the strain of the oxygen tetrahedron and the emission intensity was obtained.

Free Research Field

蛍光体、発光材料、磁性材料、半導体デバイス材料、

Academic Significance and Societal Importance of the Research Achievements

自然色に近い白色LEDの実現のためには使用する蛍光体の発光波長を的確に制御する必要があるが、現行の2価のユーロピウム（Eu2+）を発光中心とする蛍光体（Eu賦活蛍光体）は、母相の組成・結晶構造によるEu周りの配位状況の変化に応じ、赤～青までの広範囲に渡る発光波長の変化が確認されているものの、結晶場と発光波長との関係は未解明な点が多い。本研究ではESR（電子スピン共鳴）法を２種類のEu賦活蛍光体（赤色発光するCaAlSiN3:Euおよび青色発光するSr3MgSi2O8:Eu）に適用し、Eu賦活蛍光体における構造と発光波長との関係を明らかにした。これにより戦略的な発光波長の制御が可能となった。