Why am I getting temperature dependent capacitance curve of TbFeO3 in the form of an oscillating wave?

[dineshdixit]

I have multiferroic TbFeO₃ poly crystalline sample. I have put silver paste on both sides of the rectangular sample and baked at 100⁰ C for 1 hour. I have made I+, V+ contacts on one side of the sample and I-, V- on other side of the sample. The sample dimensions are following: length = 6.4 mm, breadth = 4.1 mm and thickness = 1.47 mm.

I am measuring capacitance using LCR meter which is remotely controlled by LabVIEW program. I have inserted the sample in PPMS chamber and controlling both PPMS and LCR meter using LabVIEW program. The program is not showing any error and measurement is going smooth.

I am wondering why am I getting capacitance value of the sample as an oscillating wave (please see attached file)?

Here I have used AC voltage level = 2.5 V (ALC ON)

Bias voltage = 1 V, AC frequency = 5 kHz.

I am getting similar trend for other frequencies as well.

Please comment.

Why am I getting temperature dependent capacitance curve of TbFeO3 in the form of an oscillating wave? - ResearchGate. Available from: https://www.researchgate.net/post/Why_am_I_getting_temperature_dependent_capacitance_curve_of_TbFeO3... [accessed Jan 4, 2017].

[GerdW]

Hi dineshdixit,

when you want to discuss physical/chemical behaviour of your material you should post in a forum dedicated to those problems.

When you want to discuss LabVIEW problems you should name them and post your VI(s).

Please decide what you want to do and what might be the best solution for you!

The program is not showing any error and measurement is going smooth.

As you already stated LabVIEW isn't your problem here…

[Henrik_Volkers]

How does the LCR meter output look like if you just measure a (stable) 1nF mica cap at a stable temp?

Is it possible that the signal jumps are time dependend?

Some meters do an autocal  / autozero  ....

[johnsold]

My first thought was similar to Henrik's: Determine whether the instruments are creating any kind of artifact due to range switching or something like that. If the LCR meter changes ranges at 1 nF, this could be a factor. Either turn off autoranging or change the system to move the measurement away from the edge of the range.

What is the manufacturer and model of the LCR meter?

The fact that you appear to get a data point on the downslope of the jumps makes that seem a bit less likely.

If you can get a good measurement with smaller excitation, I think that would be worth trying. The AC and bias voltages you list will result in polarity reversal across the sample.  Do you expect any non-linearities in either dielectric constant or conductivity of the samples over the temperature, voltage, or frequency ranges?

In the researchgate post you mention a temperature stabilization time of 10 ms. I know nothing of the  thermal characteristics of your sample or of the testing chamber, but that seems very quick for the size of the sample.

Lynn

[dineshdixit]

Hi johnsold,

The LCR meter is from NF Corporation and model no. is ZM2376.

I have tried by turning off autoranging. I have also tried at low AC voltage = 1.5 V and bias voltage = 0.5 V. I also tried wiith delay time = 100 ms. Nothing works, I am still getting the similar trend.

I am setting up this system as a new apparatus in the lab and I am checking the system by measuring the already reported results. The dielectric constand shows non-linerarities with temperature as described in the attached paper. 

[Henrik_Volkers]

Well, seems  that the measurement is close at the acc. limt. .. 

Have you tried a 1nF mica Cap instead? ( I would use a GenRad 1404 Air capacitor standard, but these are rare  😉 ) This is a basic test to see how your instrument behave. 

What about the jump timing?

Is it repeatable? (Not the occurence, the exact posisions!)

How is the connection done ?  Kelvin contacts? Type of wire? 

I would also try with a  short /open calibration before each measurement , with warm/hot cables! 

I like these effects 🙂  you learn a lot 😄  OK, maybe a high temp. quantum effect ?? Nobelprice !! 😄    But most probably a lag in the setup 😞  

😉

[Intaris]

Could it be that your sample / connections are not properly insulated versus ground and that you have additional effects versus ground?

[AnalogKid2DigitalMan]

I noticed that all the minima valleys occur at almost 50K temperature increments.

What does the plot of your PPMS chamber temperature ramp look like?

Could it be an artifact of the temperature control or ramp?

-AK2DM

[Ben]

In way too deep for me but...

Ferroelectrics have a hyserisis curve and I wonder if that is a factor.

Ben