Tunable structure and intensive upconversion photoluminescence for Ho3+-Yb3+ codoped bismuth titanate composite synthesized by sol-gel-combustion (SGC) method. Issue 3 (15th February 2020)

• Record Type: Journal Article
• Authors: Gao, Feng; Liu, Haifei; Ren, Feng; Wang, Kaituo; Li, Xinsheng; Wang, Youbin; He, Chunlin; Wei, Yuezhou
• Is Part Of: Ceramics international. Volume 46:Issue 3(2020)
• Page Start: 3015
• Page End: 3022
• Publication Date: 2020-02-15
• Subjects: Upconversion -- Photoluminescence -- Bismuth titanate -- Phosphors -- Sol-Gel; Ceramics -- Periodicals; Céramique industrielle -- Périodiques; Ceramics; Periodicals; Electronic journals; 666
• DOI: 10.1016/j.ceramint.2019.09.301
• Languages: English
• ISSNs: 0272-8842

Abstract

Abstract: Ho 3+ and Yb 3+ codoped bismuth titanate (BTO) composite powders with infrared to visible upconversion luminescence (UCL) function were prepared by SGC method. The effects of Ho 3+ and Yb 3+ doping content on the structure and property were investigated for BTO: x Ho, 0.2 Yb ( x = 0, 0.02, 0.04, 0.06, 0.08, 0.1) and BTO: 0.02Ho, y Yb ( y = 0.1, 0.2, 0.3, 0.5, 0.7, 0.9) samples. All the samples include three bismuth titanate phases (Bi4 Ti3 O12, Bi2 Ti2 O7, and Bi20 TiO32 ), and the phase proportion can be tuned by changing Ho 3+ and Yb 3+ doping content. These powders are well crystalized with honeycomb-like microscopic structure, and with good absorption for 233 nm, 310 nm and 975 nm wavelength. The band gap can be tuned from 3.53 eV to 4.03 eV when increasing Yb 3+ content from y = 0 to y = 0.9. A strong 530–580 nm green emission band and a relative weak 630–690 nm red one corresponding to Ho 3+ : 5 S2 → 5 I8 and 5 F5 → 5 I8 transitions appear in the UCL spectra for all the BTO: Ho, Yb samples when pumped at 980 nm. The emission intensities can well be tuned with various Ho 3+ and Yb 3+ content. The optimal UCL was obtained in BTO: 0.02Ho, 0.5 Yb for all the prepared samples. The energy transfer mechanism is analyzed by building a two-photon energy transfer model, which is proved by the relationship between emission intensities and pumping power measurement. The concentration quenching of Ho 3+ is caused by cross relaxation of CR1 and CR2 (Ho: 5 F4, 5 S2 + 5 I8 → 5 I4 + 5 I7 ) and by CR3 (Ho: 5 F4, 5 S2 + Yb: 2 F7/2 → Ho: 5 I6 + Yb: 2 F5/2 ) for Yb 3+ quenching. The mean luminescence lifetime ( τ m ) from Ho: 5 S2 decreases monotonously with the increase of Ho 3+ and Yb 3+ content.