Instruments and Measurement Set-up developed at L&FMD

  • Low temperature Solution growth workstation.
  • High temperature solution growth workstation.
  • Automatic diameter control (ADC) system (Czochralski crystal puller).
  • Vertical gradient freeze Bridgman growth workstation.
  • Accelerated crystal rotation (ACR) control.
  • Pyroelectric coefficient measurement set up.
  • High temperature poling set up (for ferroelectric domain switching).
  • Capacitive deionization (CDI) setup for water desalination.
  • ADC control system for crystal growth.
  • Control and automation software for inhouse developed Czochralski puller.
  • Software for Dielectric measurement and data logging using Impedance analyzer (HP4194A Hewlett Packard, USA) .
  • Software rutine for calculating phase matching angle for different interactions in NLO crystals.

Instruments:

1. Low temperature Solution growth workstation:

Specifications: Temp. range: 15-75 °C
        Temp. stability: ± 0.1 °C
        Temp. Gradient: ± 0.01 °C/cm
Bath capacity: 200 L Crystallizer: 20 L

2. High temperature solution growth workstation:

Three zone low gradient furnace Temperature profile
Two zone high gradient furnace Temperature profile

3. Automatic diameter control (ADC) system (Czochralski crystal puller):

Important Specifications:

   Pull rate: 0.01-20 mm/h
   Rotation rate: 0.1-20 rpm
   Load cell capacity: 8 kg (resolution: 10 mg)
   ADC: Via Proportional and Integral scheme (PI)
In-house developed ADC crystal puller

4. Vertical gradient freeze Bridgman growth workstation

For the growth of crystals by conventional Bridgman technique (growth by moving the ampule) as well as vertical gradient freezing (VGF) technique (growth by changing the temperature gradient and keeping the ampule fixed) a five zone furnace is set up. To control the temperature of each zone individual single loop temperature controllers and thyristor are used. The temperature of all the zones was monitored using K-type thermocouple. Another set of ten thermocouple are used for on-line recording of the temperature profile along the entire length of the furnace using a chart-less recorder. All the temperature controllers and monitors are interfaced to PC using RS482-RS232 converter and the chart recorder was interfaced. The monitoring of control and data logging is performed using iTools software.

Five zone VGF/Bridgman growth set up. One of the optimized gradient freezing profile as a function of time.

5. Accelerated crystal rotation (ACR) control:

Specifications:

       T1 (Ramp+dwell): 3-500 sec
       T2 (Ramp time): 1-200 sec
       T3 (Off time): 3-200 sec
       Max. RPM: 100
ACR control unit RPM profile

Set-up:

1. Pyroelectric coefficient measurement set-up:

A pyroelectric coefficient measurement set up has been developed in-house for the evaluation of pyroelectric properties of the crystals. In this method specimen is heated or cooled at a uniform rate, and the generated pyro-current is measured across a resistance. The generated pyro-voltage was recorded using high impedance Keithley make electrometer. A Kanthal make heating module was used to for heating the sample. A K-type thermocouple was used to monitor the sample temperature. The set can evaluate the pyroelectric coefficient from room temperature up to 600C. A lab view based PC interface was developed for data acquisation and logging.

The developed Pyroelectric measurement set up Screen shot showing the temperature change and
generated pyrocurrent during the measurement
Comparison of pyroelectric coefficient of
undoped, Ce and Gd SBN-61
measured using the developed set-up

2. High temperature poling set-up (for ferroelectric domain switching):

Specifications:

       Temperature range: up to 1200°C.
       Current density range: 1-20 mA/cm2
High temperature poling set up comprising of in-house developed current source module

3. Capacitive deionization (CDI) set-up for water desalination:

Specifications:

Removes salinity from 1000 ppm to less than 200 ppm
Capacity of 500 ml per batch
Removes arsenic from water from 200 ppb to less than 20 ppb.
CDI setup for water desalination CDI setup for arsenic removal

Softwares:

  • ADC control system for crystal growth.
  • Control and automation software for inhouse developed Czochralski puller.
  • Software for Dielectric measurement and data logging using Impedance analyzer (HP4194A Hewlett Packard, USA) .
  • Software rutine for calculating phase matching angle for different interactions in NLO crystals.