Growth and characterization of Scheelite crystals

A large number of tungstate (AWO4) and molybdate (AMoO4), where A' stands for large size divalent ions like Ca, Pb or Ba are naturally occurring crystals. Their scheelite structure is characterized by tetrahedrally coordinated (WO4)2-/(MoO4)2- group positioned at four corners of a unit cell and the divalent A2- located at bcc is octahedrally coordinated with oxygen ions. Though scheelites have been investigated for over 50 years, issues related to their luminescent emission still remained unresolved. In this thesis single crystal growth experiments on lead molybdate PbMoO4 (PMO), barium tungstate BaWO4 (BWO), and sodium bismuth double tungstate NaBi(WO4)2 (NBW) have been carried out using the Czochralski (CZ) technique. Structural, electronic and optical properties of these three crystals, all having the same crystalline structure were investigated experimentally as well as theoretically. Specific aspects as (a) material synthesis (b) crystal growth (c) transmission and coloration (d) photoluminescence and (e) electronic structure have been discussed in detail.

Autorentext

After joining Bhabha Atomic Research Center, Mumbai, India, in 2005 as a scientific officer, I have been mainly working on single crystal growth and characterization. Effects of non- stoichiometry and presence of foreign phases on cracking and coloration of crystals have been studied in detail.

Klappentext

A large number of tungstate (AWO4) and molybdate (AMoO4), where 'A' stands for large size divalent ions like Ca, Pb or Ba are naturally occurring crystals. Their scheelite structure is characterized by tetrahedrally coordinated (WO4)2-/(MoO4)2- group positioned at four corners of a unit cell and the divalent A2- located at bcc is octahedrally coordinated with oxygen ions. Though scheelites have been investigated for over 50 years, issues related to their luminescent emission still remained unresolved. In this thesis single crystal growth experiments on lead molybdate PbMoO4 (PMO), barium tungstate BaWO4 (BWO), and sodium bismuth double tungstate NaBi(WO4)2 (NBW) have been carried out using the Czochralski (CZ) technique. Structural, electronic and optical properties of these three crystals, all having the same crystalline structure were investigated experimentally as well as theoretically. Specific aspects as (a) material synthesis (b) crystal growth (c) transmission and coloration (d) photoluminescence and (e) electronic structure have been discussed in detail.