Crystal Growth Activity

Infrastructure has been created in the Division to grow single crystals using solution, flux, melt and optical floating zone techniques. Efforts have also been put in for indigenous development of crystal growth workstations. The characterization facilities available in the Division include XRD, FTIR, DSC, TG-DTA, polarizing light microscope, optical interferometers, thermo-luminescence set up, hysteresis loop tracer, impedance analyzer etc. The following research areas are being pursued under the crystal growth activity:

- Crystal growth from solution

- Crystal growth from flux

- Crystal growth from melt

- Major facilities

Click below for further information:

Crystal growth from solution


Some of the important developments as part of this activity are:

  • Design and development of controllers for accelerated rotation of the growing crystal inside the crystallizer in clockwise and anticlockwise directions;

  • Mercury encapsulant seeding technique for low temperature solution growth and

  • A nucleation trap crystallizer (Click to View) to arrest the growth of spurious nucleation during solution growth process.


Optical imaging of crystal growth process

Several high-precision computer-interfaced optical diagnostic systems have been set up for real time and in-situ imaging of field-parameters such as convection, concentration, growth rate and micromorphology of crystal faces during crystal growth from solution.

Shadowgraphy has been used for mapping free convection around a growing KDP crystal. The shadowgraph images have been used to quantify the free convection in terms of Grashof number and to establish a range beyond which the crystal quality becomes highly sensitive to fluctuations in concentration.
 
Growth kinetics of zinc tris (thiourea) sulphate (ZTS) single crystals was imaged in two different growth geometries to understand the evolution of polar morphology of ZTS crystals. Different chemical environments on two sides of (001) slice is suggested as a possible cause for the polar morphology of the crystals.
 
A Mach-Zehnder interferometer is being used for imaging the concentration field during KDP growth under free and forced convection conditions.
 

A Michelson interferometer has been used for imaging the surface micromorphology of prismatic and pyramidal faces of the KDP crystal. The spiral growth mechanism has been imaged in the form of concentric fringes of equal thickness. These fringes originate from the screw dislocation-generated hillocks on the crystal face.

 

Crystal growth from flux


An important developments as part of this activity is a seeding technique to minimize the wastage (dissolution) of the seed, and to establish the saturation temperature in short time.

Crystal growth from Czochralski



Crystal growth from optical floating zone


Some of the important developments as part of this activity are:

  • Automatic diameter control (ADC) system.
  • Development of a Czochralski crystal puller.
 

Major facilities

  • Indigenously developed a Czochralski puller
  • Indigenously developed automatic diameter control (ADC) system
  • Cyberstar ADC pull-head for crystal growth coupled to resistive heated furnace (high gradient and low gradient)
  • Optical floating zone crystal growth work station (CSC, Japan)
  • Refractive index measurement system (Metricon, Prism Coupler-based)
  • Differential scanning calorimetry (Rigaku)
  • Thermoluminescence (Nucleonix)
  • String-type cutter (South Bay Tech.)
  • Shadowgraph set up for mapping convective field during crystal growth from solution
  • Mach-Zehnder interferometer for mapping concentration during crystal growth and for measuring refractive index homogeneity
  • Michelson interferometer for surface structure studies
  • Birefringence interferometer for growth rate and optical homogeneity studies
  • Laser tomography set up for 3D mapping of convection and concentration during growth
  • Designed special crystallizers for interferometric & tomographic imaging
  • Optical experiments for measuring photorefractive & photoconductive properties
  • High energy ball mill (Fritsch, Germany)
  • Best viewed in 1024x768 resolution