how do i construct a thermoelectric thermometer, and what are the materials needed.
this is caused by the Seebeck Effect.
From Wikipedia http://en.wikipedia.org/wiki/Thermoelectric_effect
"The Seebeck effect is the conversion of temperature differences directly into electricity and is named after the Baltic German physicist Thomas Johann Seebeck, who, in 1821, discovered that a compass needle would be deflected by a closed loop formed by two different metals joined in two places, with a temperature difference between the junctions. This was because the metals responded differently to the temperature difference, creating a current loop and a magnetic field. Seebeck did not recognize there was an electric current involved, so he called the phenomenon the thermomagnetic effect. Danish physicist Hans Christian ěrsted rectified the mistake and coined the term "thermoelectricity".
The Seebeck effect is a classic example of an electromotive force (emf) and leads to measurable currents or voltages in the same way as any other emf. Electromotive forces modify Ohm's law by generating currents even in the absence of voltage differences (or vice versa).
The Seebeck coefficients generally vary as function of temperature, and depend strongly on the composition of the conductor. For ordinary materials at room temperature, the Seebeck coefficient may range in value from −100 μV/K to +1,000 μV/K (see Seebeck coefficient article for more information).
An absolute temperature may be found by performing the voltage measurement at a known reference temperature. A metal of unknown composition can be classified by its thermoelectric effect if a metallic probe of known composition is kept at a constant temperature and held in contact with the unknown sample that is locally heated to the probe temperature. It is used commercially to identify metal alloys. Thermocouples in series form a thermopile. Thermoelectric generators are used for creating power from heat differentials."
Essentially, what you need is to connect two wire made of different metals together tightly, connect a voltmeter to the wires and then heat the wires which will generate a voltage. This voltage can then be correlated with temperature by varying the temperature while measuring the corresponding voltage difference between the wires. Repeat this procedure at a variety of different temperatures and then make a graph comparing temperature vs voltage difference.
Also see http://www.wisegeek.com/what-is-the-seebeck-effect.htm