LSR-1

Seebeck-Coefficient & Resistivity

Description

On point

The Linseis LSR-Platform offers a user-friendly and convenient solution for characterizing thermoelectric materials, both in bulk form and as thin films. In its basic version, the LSR-1, it allows for fully automated and simultaneous measurement of the Seebeck Coefficient and Electric Resistance across a temperature range from -160°C to 200°C.

The LSR-1’s capabilities can be expanded with various options to accommodate a broader range of applications. For instance, the low-temperature option enables fully automatic measurements using LN2 cooling, extending down to -160°C and facilitating quench cooling to 80 K (for resistivity measurements only). Additionally, an optional high-temperature probe stage allows for resistivity measurements at temperatures up to 600°C. Furthermore, an illumination option is available for conducting thermoelectric measurements under controlled light conditions, utilizing a 3-wavelength LED light source integrated into the LSR-1.

The LSR-1 System is designed to facilitate the characterization of both metallic and semiconducting samples using established techniques such as the Van-der-Pauw method for resistivity measurements, static DC measurements, and slope Seebeck Coefficient measurements.

This compact desktop setup offers fully automated and software-controlled operation. The comprehensive Windows-based software provides an intuitive user interface, complete with setup wizards for defining measurement profiles, feedback mechanisms to ensure data reliability, and integrated data evaluation and storage capabilities. Moreover, the vacuum-tight measurement chamber, combined with a selection of gas dosing systems, ensures that a wide range of applications can be accommodated with precision.

Principle of Seebeck-Coefficient measurement

The Linseis system maintains precise control over sample temperature and temperature gradients through a heater embedded within the sample holder. This technology allows the environmental temperature to be cooled down to approximately -160°C, making it feasible to conduct Seebeck coefficient measurements up to a mean sample temperature of 180°C, while resistivity measurements can be made down to -160°C.

Enhanced precision in temperature measurement is achieved by employing single thermocouple (TC) wires that make contact with the sample surface orthogonally to the direction of the temperature gradient. Both contact points share the same temperature, ensuring accurate measurement of the sample surface temperature. This approach eliminates concerns related to TC wires affecting the sample surface temperature by transferring heat to or from the sample.

In the realm of thermovoltage measurement, enhanced precision is attained by measuring the Seebeck voltage between the two negative TC wires. This setup allows for the most accurate spatial alignment between temperature and thermovoltage measurement. Consequently, the Seebeck voltage occurs at precisely the same locations where temperature is being measured.

The process involves recording the Seebeck voltage alongside the temperature gradient while linearly increasing the power of the gradient heater. Each measurement sweep takes approximately 30 to 90 seconds, including high-speed sampling rates. Values are sampled once per second.

To ensure measurement accuracy, the slope of the thermovoltage over Delta T is fitted with a linear polynomial regression. This dynamic evaluation method effectively mitigates any offsets that may arise in the temperature gradient measurement, ultimately increasing measurement precision. Furthermore, the short duration of the measurement minimizes the impact of offset drifts on the results.

Principle of the resistivity measurement

To determine the specific electric resistance or electrical conductivity of a sample, the Van der Pauw measurement technique is employed. This method offers the advantage of being able to analyze samples of arbitrary shapes while effectively suppressing parasitic influences like contact or wire resistances, thus significantly enhancing measurement accuracy.

The Van der Pauw measurement involves connecting the sample with four electrodes placed at the edges. In the first step, a current is driven through two contacts on one edge of the sample, and the voltage across the other two contacts on the opposing edge is measured. These two values are then used to calculate the resistance using Ohm’s law. In the second step, the contacts are cyclically switched, and the measurement is repeated. The sheet resistance of the sample can be readily calculated by inserting the two measured resistances (horizontal and vertical) into the Van der Pauw formula and solving for it.

Based on the collected data and the thermocouple distance “t,” the specific resistance and electrical conductivity can be calculated using the following formulas:

Are you intrigued by the LSR?

Do you require further details?

Feel free to get in touch with our knowledgeable application experts!

Specifications

All facts on your hand

The Linseis system boasts a modular design, allowing for convenient upgrades with features such as a gas dosing system, illumination, and a Cryo-option to expand its capabilities.

It features a vacuum-tight measurement chamber, ensuring measurements can be conducted under precisely controlled atmospheres. The system’s user-friendly and exchangeable sample holders are equipped with integrated primary and secondary heaters.

The unit is equipped with state-of-the-art measurement electronics, which ensures the highest level of accuracy, particularly when dealing with challenging samples. It supports simultaneous measurements of both the Seebeck Coefficient and Electric Resistance (Resistivity).

The sample holder utilizes a specialized contact mechanism, making sample preparation easy and enabling measurements with high reproducibility. Additionally, the system permits V-I plot measurements to assess the quality of the sensor’s contact with the sample.

This system allows for fully automatic and software-controlled measurements with pre-defined temperature and measurement profiles. The measured raw data is stored on disk and can be exported in various data formats for post-processing in software applications like Microsoft Excel or Origin.

As part of the package, the system includes a Constantan Reference, complete with tables and a certificate to ensure precise and reliable measurements.

Model	LSR-1
Temperature range:	Basic unit: RT to 200°C* Cryo option: -160°C to +200°C*e
Principles of measurement:	Seebeck-Coefficient measurement range: 0 to 2.5 mV/K – Temperature gradient up to 10K Seebeck Voltage measurement: range +-8 mV
Atmospheres:	Inert, reducing, oxidizing, vacuum Low pressure helium gas, recommended
Sample holder:	Integrated PCB Board with Primary and Secondary Heater
Sample size (Seebeck):	L: 8 mm to 25 mm; W: 2 mm to 25 mm; T: thin film to 2 mm
Sample size (Resistivity):	L: 18 mm to 25 mm; W: 18 mm to 25 mm; T: thin film to 2 mm
Vaccum pump:	optional
Heating rate:	0.01 – 100 K/min
Temperature precicion:	±1,5 °C oder 0,0040 ∙ \| t \|
Electric Resistivity:	10 nOhm
Thermovoltage:	0.5 nV/K (nV = 10-9 V)

Software

Make values visible and comparable

The LINSEIS thermal analysis software, a robust Microsoft® Windows®-based application, plays a pivotal role in the preparation, execution, and evaluation of thermoanalytical experiments, complementing the hardware it interfaces with. This software package offers a comprehensive solution for programming device-specific settings, controlling functions, and managing data storage and evaluation. It has been meticulously developed by our in-house software specialists and application experts, with a track record of proven performance over the years.

Key features and properties of the software include:

Automatic Evaluation of the Seebeck Coefficient and Electrical Conductivity
Automated Control of Sample Contacting
Creation of Automatic Measurement Programs
Development of Temperature Profiles and Gradients for Seebeck Measurements
Real-time Color Rendering
Automatic and Manual Scaling
Flexible Axis Representation (e.g., temperature on the x-axis and delta L on the y-axis)
Mathematical Calculations (e.g., first and second derivatives)
Database for Archiving Measurements and Evaluations
Multitasking Capability (Running Different Programs Simultaneously)
Multi-User Option (User Accounts)
Zoom Options for Analyzing Curve Segments
Overlapping Display of Multiple Curves for Comparison
Online Help Menu
Customizable Curve Labels
Streamlined Export Functions (including CTRL C for copying)
Export Data to EXCEL® and ASCII Formats
Statistical Trend Evaluation (Mean Value Curves with Confidence Intervals)
Tabular Representation of Data

The LINSEIS thermal analysis software provides a comprehensive platform for researchers and analysts to efficiently conduct experiments, visualize data, and draw meaningful conclusions from their thermal analysis studies.

Applications

Application example: Evaluation acquired data through linear regression

The Seebeck voltage over the temperature gradient is depicted in blue, measured while varying the gradient heater power. This measurement is accompanied by a linear regression analysis, illustrated in red.

Seebeck coefficient is determined by the slope of the linear regression.

Application example: Data evaluation

In this approach, the Seebeck coefficient is measured in relation to Alumel. To determine the absolute Seebeck coefficient, measurements are conducted by comparing Platinum to the Alumel wire across a range of temperatures.