# Presentation: 694812

## The Spectroscopic Study of Cr4+ Doped CaO-GeO2-Li2O-B2O3(Al2O3) transparent glass-ceramics

- Presentation by: Victor Ortiz
- School: M.S./H.S. 141 David A. Stein Riverdale/Kingsbridge Academy
- Mentor: Dr. Alexei Bykov, Prof. V. Petricevic
- IUSL-Physics Department

**Notes:**
Hello everyone, my name is Victor Ortiz and I am a upcoming senior at Riverdale/Kingsbridge Academy. My Mentor is Dr. Bykov and I will be speaking about our research, which is the Spectroscopic Study of Cr4+ Doped Calcium Germanium transparent glass-ceramics. 

## Introduction

**Study the behavior of Cr-doped Calcium Germanium glass media during synthesis and devitrification (i.e., heat treatment)**
**A number of glass compositions yield transparent glass-ceramics after heat treatment**
**Crystallites ≤ 1********m**
**Cr doped glass ceramics exhibit a broad band of fluorescence (1000-1600nm wavelength; peaking at 1280nm).**
**Optical properties similar to CUNYITE crystals (i.e.,Cr****4+****: Ca****2****GeO****4**** )**
**Absorption and Fluorescence Spectra of the samples help better understand the optical properties of glass-ceramics**

**Notes:**
We have been studying the behavior of Cr-doped Calcium Germanium glass media during synthesis and heat treatment. A number of these glass compositions yield transparent glass-ceramics after heat treatment. Glass ceramics? This is a material that shares both properties of glass and crystals, crystallites have formed within the glass media. We estimated that the size of these crystallites to be less than 1 μm. When excited, these glass ceramics exhibit a broad band of fluorescence between the wavelengths 1000-1600nm; peaking at 1280nm. This show that the optical properties are similar to that of CUNYITE bulk crystals. We measure the absorption and fluorescence spectra of these glass ceramics to help better understand the optical properties. Now, CUNYITE is a stable laser material that was developed here at CCNY. So if we are ready have this material, then why are we developing this Cr-doped glass ceramic. Well, that’s because this new material takes a shorter period of time to synthesis, it’s  less expensive, And doesn’t need the heavy instruments that CUNYITE needs.    

## The use of the Confocal Microscope is a new approach to a better view and understanding of the nanoscale crystallites
Cr-doped glass ceramic emits fluorescence in NIR spectrum 
Manganese (II) Carbonate emits fluorescence in visible spectrum    

- To create new materials for optical amplifiers and fiber-lasers to enhance **telecommunication systems** and ***remote LIDAR*** applications

**Summer Research Objective**

- To find the optimal temperature and time required for mass crystallization of nanoscale crystallites

**New Methods For Analyzing Crystallites **

**The use of the Confocal Microscope is a new approach to a better view and understanding of the nanoscale crystallites**
**Cr-doped glass ceramic emits fluorescence in NIR spectrum **
**Manganese (II) Carbonate emits fluorescence in visible spectrum**

**Notes:**
Our long term goal is create new materials for optical amplifiers and fiber-lasers to enhance telecommunication systems and remote LIDAR applications. My summer research objective is to find the optimal temperature and time required for mass crystallization of these nanoscale crystallites. Recently, we began researching on a new method for analyzing the crystallites. Two words came to mind, Confocal Microscope. With the aid of the confocal microscope, we will gain a better view and understanding of the nanoscale crystallites. But an problem occurred, the Cr-doped glass ceramic emits fluorescence NIR range, which the confocal microscope can-not pick up Cleary. So we are temporary replacing Chromium with Manganese (II) Carbonate, which is a good light emitter. It emits fluorescence in the visible spectrum. Which the confocal microscope can pick up.   

## Recipe for Manganese-Doped Calcium Germanium Glass [2.0 CaO – 1.0 GeO2 – 1.0 Li2O – 0.5 B2O3 – 0.2 (Al2O3) – 0.04 (P2O5)]

**CaCO3 – Calcium Carbonate**
**Li2CO3 – Lithium Carbonate**
**GeO2 – Germanium Oxide**
**B2O3 – Boron Oxide**
**Al2O3 – Aluminum Oxide**
**NH4H2PO4 – Ammonium Dihydrogen Phosphate**
**MnCO3 – Manganese (II) Carbonate**

**Mn-doped Glass Media**

**Checkpoint**

**Powders**

**Liquid**

**Solid**

**Notes:**
These are the procedures taken in order to create the Manganese-doped Calcium germanium glass. First we weigh the chemicals and mix them into a mortar. This is a list of the chemicals we use to create the glass media. All the chemicals from Calcium Carbonate to Ammonium Dihydrogen Phosphate, are necessary to create the glass media. The manganese Carbonate is the only variable in this mixture. These chemicals all are powders. Once we have completing mixing the chemicals, they are place on a crucible and into a furnace at 800°C in order to release carbon. This is so there won’t be any bubbles within the glass media once completed.     

## Experimental Protocol

## Cr-doped Glass Media

**8 hour in 501°C**

**No heat treatment**

**1 hour in 520°C**

**Few crystallites formed**

**A large number of nanoscale crystallites were formed or a few numbers of large size crystallites   **

## All Materials absorb radiation in some ranges of the electromagnetic spectrum

- The term is used to describe the entire range of light radiation (gamma rays to radio waves)
- The amount of absorption depends of the wavelength, the amount of absorbing material in the radiation path, and absorption of that material at that wavelength

**Notes:**
Before I show you an absorption spectra, I would like to explain to you all a little about “what absorption is”. All materials absorb radiation in some ranges of the electromagnetic spectrum. What is this electromagnetic spectrum? Well, it is a term used to describe the entire range of light radiation, which is from gamma rays to radio waves; as shown here. 

## Absorption of Cr-Doped Glass Media

***The higher the absorption, the more light will scatter on crystallites in glass ceramics. Larger size of crystallites****.*

***The lower the absorption, the less light will scatter on crystallites in glass ceramics. Smaller size of crystallites****.*

**1 hour in 520°C**

**8 hour in 501°C**

_***Absorption of Cr-Doped Glass Media***_

## Measuring Fluorescence Spectrum 

-  Fluorescence spectrum is the amount of electromagnetic radiation the atom emits when it is excited.
-  When electrons in the element are excited, they jump to a higher energy level. Solid mediums tend to absorb light and store it as heat. As the electron falls back down and leave the excited state, light is re-emitted at longer wavelengths with less intensity.

**Ground State**

**Light**

**Fluorescence**

**Excited State**

**Electron**

***680-nm laser***

## Fluorescence of Cr-Doped Glass Media

***Maximum of broad band emission***

_***Fluorescence of Cr-Doped Glass Media***_

## Mn-doped Glass Media

**20 hours in 495°C**

**45 minutes in 560°C**

**No heat treatment**

**Crystallites were formed within the glass ceramic, reasons for color changed are still unknown**

**A small number of crystallites have formed, glass ceramic still transparent**

## Absorption of Mn-Doped Glass Media

**45 Minutes in 560****°C**

**10 Hours in 495****°C**

_***Absorption of Mn-Doped Glass Media***_

## Fluorescence of Mn-Doped Glass Media

## Conclusion 

- Crystallization in glass media varies according to temperature and heat treatment time.
- Chromium-doped glass ceramics emit fluorescence around wavelengths of 1200-1300nm, similar to CUNYITE crystals.
- Manganese-doped glass ceramics is expected to have a broad band fluorescence between 550~700nm when excited at 488nm.
- The change in color is believed to have to occur due to crystallization all inside of the Mn-doped Glass Media.
- The behavior of this substance is still unsure

**Notes:**
Yellow to red

## Future Plan

**Study optical properties of crystallites with Mn-doped glass media with confocal microscope**
**Compare the crystallites within the Mn-doped media with that of Cr-doped media**
**Decide another metal to doped depending of results  **
**Continue running experiments with Cr-doped glass media and any other metal-doped glass material**
**Long term goal is to create a new material for optical amplifiers and fiber-lasers to enhance telecommunication systems**

## Reference

- “Confocal microscopy of colloids” V Prasad, D Semwogerere, ER Weeks, J. Phys.: Cond. Mat. 19, 113102 (2007)
- _Synthesis and characterization of Cr__4+__ -doped CaO-GeO__2__-LiO-B__2__O__3__(Al__2__O__3__) transparent glass-ceramics_ by A.B. Bykov, M. Yu Sharonov, V. Petricevic, I. Popov, L.L. Isaacs, J. Steiner, and R.R. Alfano
- _Optical Properties Measurements of Laser Crystals_ by Dr. A. Bykov
- _Guide for Absorption and Fluorescence Spectroscopy_ by Mr. G. C. Tang and Prof. R. R. Alfano
- _Spectroscopic study of chromium-doped transparent calcium germanate glass-ceramics_ by M. Yu. Sharonov, A.B. Bykov, T. Myint, V.Petricevic, R.R Alfano

- NASA Goddard Space Flight Center (GSFC)
- NASA Goddard Institute for Space Studies (GISS)
- NASA New York City Research Initiative (NYCRI)
- The City College of New York (CCNY)
- Dr. Alexei Bykov, Prof. V. Petricevic
- Dr. Frank Scalzo, Dr. Manuel Zevallos, Mr. Daniel Moy
- Mr. Jose Lai, Mr. Jorge Franco
- Mr. David Deutsch, Ms. Charlene Chan-Lee

***Acknowledgements***