CaltechTHESIS
  A Caltech Library Service

Scintillation mechanisms of cerium-doped rare earth oxyorthosilicates

Citation

Suzuki, Hideyuki (1994) Scintillation mechanisms of cerium-doped rare earth oxyorthosilicates. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-10182005-130418

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.

Rare earth oxyorthosilicates (RE)2(SiO4)O (RE = rare earth) have high densities and effective atomic numbers for efficient gamma-ray detection. Among these, Gd2(SiO4)O, Y2(SiO4)O and Lu2(SiO4)O have no absorption lines at visible wavelengths and thus were examined as potential single crystal scintillators by doping with cerium (Ce).

The light emission mechanism of the activator Ce3+ ion in (RE)2(SiO4)O was investigated with UV light, by selectively exciting absorption bands of Ce3+ at low temperature (~11 K). It was found that all three compounds have two types of excitation and emission spectra and decay constants, and they were attributed to two Ce3+ centers (Ce1 and Ce2) occupying two different host rare earth sites.

The origins of two decay constants in the gamma-ray excited decay of Gd2(SiO4)O:Ce (GSO) were investigated. We focused on GSO since the gamma-ray excited decay times of GSO are much slower than the intrinsic Ce3+ decay, in contrast with Y2(SiO4)O:Ce and Lu2(SiO4)O:Ce. Since Gd3+ emission bands overlap Ce3+ absorption bands, the energy transfer from Gd3+ to Ce3+ was analyzed for a possible explanation for the slow Ce3+ decays. The Gd3+ absorption bands in the UV region were excited by a synchrotron light source and the Ce3+ decay was monitored. With excitation into the [...] and [...] states of Gd3+, a slow decay component and a build-up were observed in the Ce3+ decay, consistent with energy transfer from [...] and [...] states of Gd3+ to Ce3+.

The energy migration through the Gd sublattice in GSO was investigated. The Gd was diluted by optically inactive rare earths, Y and Lu, and the macroscopic energy transfer rate from Gd3+ to Ce3+ was measured as a function of Gd concentration. The results show that the macroscopic transfer rate from Gd3+ to Ce3+ increases as Gd concentration increases, indicating that the energy of the excited Gd3+ can migrate through the Gd sublattice before one of the Gd3+ near a Ce3+ can transfer its energy to the Ce3+.

Item Type:Thesis (Dissertation (Ph.D.))
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Materials Science
Thesis Availability:Restricted to Caltech community only
Research Advisor(s):
  • Tombrello, Thomas A.
Thesis Committee:
  • Unknown, Unknown
Defense Date:1 February 1994
Record Number:CaltechETD:etd-10182005-130418
Persistent URL:http://resolver.caltech.edu/CaltechETD:etd-10182005-130418
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:4160
Collection:CaltechTHESIS
Deposited By: Imported from ETD-db
Deposited On:19 Oct 2005
Last Modified:26 Dec 2012 03:05

Thesis Files

[img] PDF (Suzuki_h_1994.pdf) - Final Version
Restricted to Caltech community only
See Usage Policy.

4Mb

Repository Staff Only: item control page