MiniFlex Training

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MiniFlex Training

• Instructions on the care and operation of the
  Rigaku MiniFlex X-ray Diffractometer

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Topics to be covered

• X-ray Safety
• System Maintenance
• Sample Preparation
• Data Collection
• Data Processing using MDI JADE

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X-ray Safety
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Hazards of X-ray Radiation

• X-rays are energetic electromagnetic radiation
  that ionize matter by ejecting electrons from
  atoms
• The extent of ionization, absorption and
  molecular change depends upon the quality
  (spectral distribution) and quantity (flux and
  intensity) of the radiation

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Hazards of X-rays (contd)

• Living organisms can be injured by exposure
• Type and extent of injury is a function not only
  of quality and quantity of radiation, but also
  duration of exposure and distance from source

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Hazards of X-rays (contd)

• X-rays are INVISIBLE, so its impossible to see
  the path they take
• However, the strongest intensity lies along the
  path of the DIRECT BEAM
• Intensity from a scattered beam is MUCH LESS than
  the direct beam

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Inverse Square Law applies. Intensity decreases
with the square of the distance.
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MiniFlex Hardware

• How to identify various system components

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MiniFlex
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Water Chiller
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X-ray Tube Cross-section
Here is a picture of the glass insulated tube,
sometimes called the European Standard tube. It
comes in Long and Short Anode versions. The
MiniFlex uses the Long Anode version. The Anode
is a copper block onto which is welded the
target. If no material is added the tube is
copper. Other typical target materials are
chromium, cobalt, molybdenum, and tungsten.
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MiniFlex (with the hood up)!
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Tube Height Adjustment
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Divergence Slit andSample Stage
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Diffracted Beam Opticsand Detector
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Kß Filter Only
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Absorber on Kß Filter
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Correction Angle(adjust with every stage change)

• The Correction Angle is determined by scanning
  over a major peak of a standard (like Si 111
  which occurs at 28.4422? for Cu K? radiation)
  and calculating the correction.
• Si 111 for Chrome42.832 2? for Fe35.965
  Co33.151Mo 12.989

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Correction Angle (contd)

• In MANUAL MEASUREMENT Under Control select
  Measurement
• Setup scan as above
• Press Execute

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Correction Angle (contd)
Press Execute under Peak Search to locate top of
peak
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Correction Angle (contd)

• Correction Peak Position - 28.44 0.02
• Enter 0.02 as Correction Angle in Setting
• Press Execute
• Re-measure

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Correction Angle (contd)
Peak is within 0.01 of reference value for
standard
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Detector HV/PHA

• The Pulse Height Analyzer (PHA) is hard wired
  and cannot be adjusted.
• Detector High Voltage (HV) is adjusted to give
  the greatest intensity.

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Detector HV/PHA (contd)

• In Manual Measurement Under Control select
  Independent mode. Select 28.44 as the target
  angle (for Cu tube). Press Execute.
• Press SCHV/PHA.

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Detector HV/PHA (contd)

• Setup HV Scan as indicated below.

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Detector HV/PHA (contd)
Press Execute under Peak Search to locate HV value
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Detector HV/PHA (contd)
Enter HV value in Control Setting
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MiniFlexSystem Maintenance

• Procedures to ensure safe operation and optimal
  performance

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MiniFlex System Maintenance

• Cleaning
• Chiller
• MiniFlex
• System Checks
• Log Records

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Cleaning the Chiller

• Check the grill for dust buildup. Remove with a
  paint brush if necessary.
• Check water. If it looks cloudy due to green or
  brown algae, flush and change with fresh
  DISTILLED WATER.

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Cleaning the Chiller (contd)

• Never add TAP or DEIONIZED WATER. Tap water
  contains minerals that may clog a filter inside
  the tube cap. Deionized waters pH can actually
  damage the x-ray tube.

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Cleaning the MiniFlex

• Check for dust and dirt buildup
• Card cage
• Floor of measuring chamber

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Cleaning the MiniFlex

• To clean dust from card cage
• Use a can of compressed air to blow out as much
  as possible. If big particles remain you can
  call Rigaku Service to remove them or carefully
  remove the board (POWER OFF!) and do it yourself.

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Cleaning the MiniFlex

• Cleaning the floor of the measuring chamber
• Usually consists of sample debris
• Recommend using rubber glover and face mask
• Use a piece of paper and a small brush
• Carefully sweep the debris away using the paper
  as a dustpan.

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System Checks

• System should be checked
• Weekly A sample (like Silicon) should be checked
  for
• Peak Position of 111 reflection (28.442?)
• Intensity of 111 reflection
• Peak Width of 111 reflection
• Log results along with operator and date

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System Checks (contd)

• Monthly Same standard is thoroughly checked for
• Weekly check plus
• Scan from 25 to 902?
• Use JADEs Theta Calibration (Linear Fit) to
  determine Calibration Curve

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Sample Preparation

• How to prepare various kinds of samples to obtain
  optimal data

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Applications
X-ray Diffraction (XRD) analyzes a wide variety
of solid samples. Why solid? Because it needs
the interaction of x-rays with the crystalline
structure. Most solids have a crystalline
structure that is stable. Glasses are the
exception, but even they have structure. Some
examples where XRD is used Chemicals Geology
(mineralogy, oil exploration) Metallurgy Polymers
Catalysts
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XRD Information

• Each diffraction pattern contains sets of
  information
• Set of local diffraction maximum positions
• Set of intensities for those positions
• Set of intensity distribution as a function of
  the diffraction angle (2?)

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Common Errors found in XRD Data

• Sample Displacement
• Sample Transparency
• Sample Flatness
• Sample Particle Size
• Axial Divergence
• Preferred Orientation

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Sample Displacement

• Probably the most common and largest source of
  error in diffraction data.
• Sample sits above or below Measuring Circle
• Shifts peak position 0.01 for every 60 ?m

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Sample Displacement (contd)
Measuring Circle
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Sample Displacement (contd)
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Sample Transparency

• Error caused by diffraction from below the
  surface of a low absorbing sample
• Asymmetrically broadens peaks
• Change in 2? is a function of sin2?
• Maximum effect at 902?

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Sample Transparency (contd)
Measuring Circle
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Sample Transparency (contd)
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Sample Flatness

• Sample surface should be as Flat as possible
• Measuring circle changes curvature with 2?
• Peaks shift towards lower 2?
• Broadens peaks asymmetrically
• Maximum effect at small 2? angles

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Sample Flatness (contd)
Measuring Circle
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Sample Flatness (contd)
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Particle Size

• Particles must be small enough to
• allow x-rays to penetrate to core
• pack to provide a flat surface
• Usually that means -325 mesh (lt45?m), but if the
  sample has heavy elements -500 mesh may be
  required
• Spinning the sample helps

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Axial Divergence

• X-rays travel transverse as well a straight,
  which means they travel a longer distance
• This error can be reduced with finer soller slits
  (hardware) (but not on the MiniFlex)
• Maximum at low 2?. Minimum at 90 2?.

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Axial Divergence (contd)

• Soller Slits prevent x-rays the deviate more than
  X from straight from being counted

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Preferred Orientation

• Samples crystals line-up or stack in such a way
  that certain reflections appear more intense than
  normal
• Typical in clays and micas
• Spinning sometimes helps
• Special sample preparation may be required

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Sample Holders
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Zero Background Holder
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Top Loading Holder
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Back Filled Holder
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Steps for Preparing a Back Filled Holder

• Place empty holder on a flat surface, like a
  large glass slide
• Pour in just enough sample to fill cavity.
  ESTIMATE!
• Using a second glass slide pack the sample into
  the cavity as tightly as possible

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Steps for Preparing a Back Filled Holder (contd)

• While holding onto both slides plus sample,
  INVERT carefully.
• Remove top slide exposing the surface that was on
  the bottom.
• If sample holds in place, remove bottom slide.
  Otherwise, insert holder plus bottom slide into
  system

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MiniFlex Data Collection

• How to collect XRD data using the Standard
  Measurement program

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Standard Measurement Icon

• Locate this icon on the screens desktop
• Double-click to start program

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Standard Measurement

• Press Measurement condition to setup conditions

Main Screen
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Measurement Conditions
Measurement Method CONTINUOUS degrees
per Minute. Column header reads Scan Speed
Continuous Measurements
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Measurement Conditions
Measurement Method FIXED TIME Seconds dwell per
step. Column header reads pre-set time.
Fixed Time Measurements
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Measurement Conditions

• Click on scan to duplicate
• Check Dupli
• Press Execute

Duplicate Scan
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Measurement Conditions

• Click on scan to delete
• Check Delete
• Press Execute

Delete scan
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Setup Samples

• Make sure Use is set to YES
• Specify Directory name, if different
• File name must end with a .raw extension for
  JADE to read the file.

Setting up First Sample
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Setup Samples

• Select sample to duplicate
• Check Dupli
• Press Execute
• Complete File name, Sample name, and Cond. No.
  fields

Setting up Additional Samples
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Setup Samples

• Click on sample to delete
• Check Delete
• Press Execute

Deleting samples
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Setup with Sample Changer
Press here to setup Spinning

• Specify samples position on carousel (1-6).
• Samples do not have to be in order

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Start Data Collection

• Press Measurement Start to start data collection

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Data Collection Tips

• Pre-Scan sample to determine efficient data
  collection conditions (2-80 2?, 0.05 step at
  20 /minute).
• To increase counting statistics, count 5 times
  longer.
• To reduce noise, do 5 quick repeats. Crystalline
  signal is constant noise signal is variable.
  Average scans together in JADE.

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Utilize The Extra Scan Conditions

• There are 50 measuring conditions and 20
  individual conditions for each1000 scans.
• If you have multiple users, consider giving each
  person a separate condition number.
• Set up frequently used conditions and turn them
  On or Off as needed.
• Keep Standards, such as the Weekly or Monthly Si
  (111) on a separate condition.