MiniFlex Training

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

Topics to be covered

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

X-ray Safety

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

Hazards of X rays (cont’d)

• 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

Hazards of X rays (cont’d)

• 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

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

MiniFlex+ Hardware

How to identify various system components

MiniFlex+

Water Chiller

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.

MiniFlex (with the hood up)!

Tube Height Adjustment

Divergence Slit and Sample Stage

Diffracted Beam Optics and Detector

Kß Filter Only

Absorber on Kß Filter

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 28.442

°2  for Cu K  radiation) and calculating the correction.

• Si 111 for Chrome=42.832 °2  ; for Fe=35.965; Co=33.151;Mo= 12.989

Correction Angle (cont’d)

• In MANUAL MEASUREMENT Under Control select

Measurement

• Setup scan as above • Press

Execute

Correction Angle (cont’d)

Press

Execute

under Peak Search to locate top of peak

Correction Angle (cont’d)

• Correction = Peak Position - 28.44° = 0.02

• Enter

0.02

as Correction Angle in

Setting

• Press

Execute

• Re-measure

Correction Angle (cont’d)

Peak is within ±0.01° of reference value for standard

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.

Detector HV/PHA (cont’d)

• In Manual Measurement Under Control select

Independent mode.

Select 28.44

° as the target angle (for Cu tube). Press

Execute

.

• Press

SCHV/PHA.

Detector HV/PHA (cont’d)

• Setup HV Scan as indicated below.

Detector HV/PHA (cont’d)

Press

Execute

under Peak Search to locate HV value

Detector HV/PHA (cont’d)

Enter HV value in Control

Setting

MiniFlex+ System Maintenance

Procedures to ensure safe operation and optimal performance

MiniFlex+ System Maintenance

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

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.

Cleaning the Chiller (cont’d)

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

Cleaning the MiniFlex

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

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.

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”.

System Checks

• System should be checked:  Weekly: A sample (like Silicon) should be checked for:   Peak Position of 111 reflection (28.44

°2  ) Intensity of 111 reflection   Peak Width of 111 reflection Log results along with operator and date

System Checks (cont’d)

 Monthly: Same standard is thoroughly checked for:    Weekly check plus Scan from 25 ° to 90°2  Use JADE’s

Theta Calibration (Linear Fit)

Calibration Curve to determine

Sample Preparation

How to prepare various kinds of samples to obtain optimal data

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

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  )

Common Errors found in XRD Data

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

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

Sample Displacement (cont’d)

Measuring Circle

Sample Displacement (cont’d)

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 90°2 

Sample Transparency (cont’d)

Measuring Circle

Sample Transparency (cont’d)

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

Sample Flatness (cont’d)

Measuring Circle

Sample Flatness (cont’d)

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 (<45  m), but if the sample has heavy elements -500 mesh may be required • Spinning the sample helps

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  .

Axial Divergence (cont’d)

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

Preferred Orientation

• Sample’s 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

Sample Holders

Zero Background Holder

Top Loading Holder

Back Filled Holder

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

Steps for Preparing a Back Filled Holder (cont’d)

• 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

MiniFlex Data Collection

How to collect XRD data using the Standard Measurement program

Standard Measurement Icon

• Locate this icon on the screen’s desktop • Double-click to start program

Standard Measurement

• Press

Measurement condition

to setup conditions Main Screen

Measurement Conditions

Measurement Method CONTINUOUS = degrees per Minute.

Column header reads Scan Speed

Continuous Measurements

Measurement Conditions

Measurement Method FIXED TIME= Seconds dwell per step.

Column header reads pre-set time.

Fixed Time Measurements

Duplicate Scan Measurement Conditions

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

Delete scan Measurement Conditions

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

Setting up First Sample 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 Additional Samples Setup Samples

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

Deleting samples Setup Samples

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

Setup with Sample Changer Press here to setup Spinning

• Specify sample’s position on carousel (1-6).

• Samples do not have to be in order

Start Data Collection

• Press

Measurement Start

to start data collection

Data Collection Tips

• Pre-Scan sample to determine efficient data collection conditions (2-80 ° 2θ, 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 .

Utilize The Extra Scan Conditions

• There are 50 measuring conditions and 20 individual conditions for each —1000 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.