Titanates and Electronic Devices

Barium Titanate, actually. (BaTio3, I think)

Regards

After sending my response I Googled; and you're right; sodium bismuth titanate and potassium titanate as well as barium titanate are used as ceramic capacitors. A lot of info available on the Web.

Regards

Ceramic capacitors (and many other useful piezoelectric devices) are made from a family of ferroelectric compounds called "Perovskites". These include various titanates or niobates, such as barium titanate, calcium titanate, strontium titanate, lead titanate, and magnesium titanate and mixtures of the above. In addition, other ingredients such as oxides of metals such as neodymium, samarium, zirconium are often added to make capacitors with certain desired characteristics. These properties can include extremely high dielectric constant, low dielectric loss, low temperature coefficient, low voltage coefficient, etc.

Recently, new formulations using sodium bismuth titanate have been found to have high dielectric constant and superior performance at elevated temperatures. Because of the close chemical similarity between sodium and potassium, it may indeed possible to fabricate capacitors using a potassium titanate dielectric. And, there are commercial ferroelectric devices that use potassium niobate.

The following is an additional source of information that you may find useful:

http://www.activesignaltech.com/Capacitors1.html

Bert

Capacitor is by defination a pervosite structure (or layered structure) alternating between ceramic layer like titanate and others and metal layer to transmit charge for storage and take it out for use when it is needed.

Basic requirement is ability of material is to polarize and hold on the to polarization as storage device for power. To do this we need to have bulky atoms like barium, titanaium, stronitium and others.

sodium, potassium and others small diameter ions has poor ability to store power. They are ionic conductor and not a capacitor materials. They are used to make manufacturing of capacitor managible in the lower temperature so we can use conventional furnace but capacitor quality degrades.

This is reason we have lower grades like X5R and higher common grades X7R and very high grade X8R and X9R. Each is based on the reliability needs. Lower grades are made around 700 to 1100C and higher grades are above 1400C. Upper grade is free of sodium and potassium

If I need a compact high-value capacitor and my maximum operating temperature is 125 degrees, wouldn't I usually be better off using X7R than X8R? Do you have evidence that X7R is less reliable than X8R at these temperatures?

So how does that make X8R a higher grade? It's a higher-temperature grade for sure, but are there any other advantages?.

Yes X8R is better quality than X7R. At end of the day one looks for reliability. If you are designing delivery system which will deliver 1 ft or 100 ft range decides the component used.

In 1ft we end up using 6sigma quality and go with X9R and 10 most of the design is in X8R and cheaper is in X7R.

If it 99C digital watch you can not go more than X5R.

It is the reliability and needs which dictates the quality.

More than 90% of the high end product has X7R but 10% critical component needs are X8R and X97.

You can always send email or chat on this subject via my email Masyood@gmail.com

Can you provide a reference to support your view that X8R capacitors are more reliable than qualified X7R grades? Thanks.

It's obvious that X7R will not provide performance while you are exceeding its operating conditions, but it still appears to be reliable following long-term storage at high temperature and following multiple temperature excursions. On which topic, I have analysed failures of ceramic capacitors in the past*, and the only "dielectric-related" failures that I have ever seen were where the manufacturing process was not properly designed and/or monitored to prevent delamination during initial manufacture (and even there, it is my understanding that the principal cause was organics that were introduced along with the metallisation). Electrode and termination issues also occur, and I can imagine that higher manufacturing temperatures may allow (maybe even require?) more robust electrodes, so I can see what you say is possible. However, by far the most common causes of failure I have seen for properly screened components (in environments ranging from submerged telecomms through aerospace to ground-test of space components) have been due to assembly issues and contamination.
My present understanding is that X7R and even X5R capacitors are available with1-FIT reliability provided you derate them suitably to match the required operating temperature (derating specs for X7R). (And I cannot see why the dielectric type would be a limiting factor, even down to much lower failure rates)

*It's a while since I worked on component reliability, so the nominal standards (nearly always exceeded once the systems were actually in place) were mostly in the 3-10 FIT range. I believe the identical components would now receive a 1-FIT rating. (For those without the field, ft or FIT is a measure of failure rate = one Failure In every 10⁹ hours)

This is healthy and good discussion. I also have few patents and during my development of capacitor end termiantion and work on improving relaibility of the capacitor in field few things are clear to me which I wrote a patent disclouser filed but never allowed to publish. Since it is old I will try to walk you through that and hope you will agree

1. When prople say it is termination and electrode this is half true. Full truth is it is triple junction point which is weakest link and that is ceramic-electrode and termiantion. --> I did looked in this and find a way to improve the termination performance in the field for extreme condition use capacitors.

2. Body failure like start burst or Haley trail type is purely carbon when resistance acrcoss the layer is less than within layer and carbon trace across the layer you can observe. --> I did when I needed to optimize the body you can solder small wire and put in SEM and start applying voltage and come close to failure but does not allow failure to occur. Take the capacitor out remove one side and go through copper plating the copper removed surface. What you will observe is copper inner deposition in the area where the failure started and what you will find is you have carbon particulate there. This work was needed when you start developing X8R and X9R type capacitor which you want to have reliability at elevated temperature than X7R.

3. You control the alkali ions in PPB level instead of PPM level

and I can keep going if you have further interest

Masyood Akhtar Ph.D.

Masyood@gmail.com

1) Agreed, but I was talking about the origin of the problem, and abbreviated carelessly. What was important (than) was that in production the organics don't so often arrive with the dielectric (though I have known occasions when lab-results were distorted because the binder wasn't properly driven off). What often leads to confusion is that acoustic images as often show the carbon-induced separations as 'within the dielectric' than in the boundary, even when the origin is impurities introduced with the metals.

2) Carbon comet-like traces: yes. I've seen something like that.

But, although I understand that we need the higher-numbered dielectrics to give operation at higher temperatures, I don't understand that they would be needed for the levels of reliability you quote. (But that really has little to do with alkali content - SFIK X7R does not after all require any of that)

3) contaminants: coming a little closer to my longer-term area of work, there are similar issues in semiconductors - with alkali metals being significant in the insulators at similar levels to those you report.
But it's a different issue where they form part of the structure - so personally I wouldn't necessarily discount using Na or K (or even Li) -based Perovskites in high-reliability capacitors)

I tried to fix alkali ions ones you mentioned but after 20 years and Ph.D. in glass, M.S. in Ceramics and B.S. in Metallurgical Engineering failed to do that reliably. I am able to develop new materials which is not oxide, not metal and not semoconductor but not able to fix single valance inoic materials. You can bond but it it goes through migration under potential and load. It is matter how fast or slow.

Good to know you belive we can do that. Seperation you see is delamiantion. Delamination is caused by poor lamination during green work of laying down under isostatic pressure of heat and unidirectional load.

In earlier if not done correctly it will be in innder body and if it not in inner body then generally near surface.

If it is from Japan like TDK and Murata it will be sequencial. If it is Kemet it will be near surface and if is AVX or Yagoo it will be at around central

And this dielactric lamiantion

Carbon is improper ramp and soak. It also happens based on poor thermal profile and poor binder quality but a good engineer will figure it out.

Triple point defect is pure materials problem and can be solved with addition of new amterials in termiantion paste

I don't believe "I can do it" within your families of materials, which I suspect to be what you tried. But I have worked with many kinds of single-crystal Perovskite that incorporate alkali ions, and the moving ion problem does not arise until the temperature is several hundreds of degrees. (The only Perovskite that I worked on where I saw evidence of a mobile-ion problem was actually the near-ubiquitous LiNbO₃)

You are very correct. If you fix alkali ions they are fixed to a temperature as of onces ability to understand and fix it. When it is fixed then its polarizability ability gives polaric movement to alkali ions and this one can use for nano weight m/c development using this deflection. Example of fixing just I am highlight one is below

In glass we all know boron stays in planer structure and is very suseptable to mositure absorption. People can add sodium ions to convert planer to tetrahedral boron structure and provide stability to boron from positure stability. This is sodium (alkali ions fixing). This technology practical used is in development of crack cement driways and old brick structure by having liquid silica poured where sodium at room temperature stablizes with calcium in the cemnt.

Same is true in titanate field. To make cheaper capacitor like X5R people put Sodium chloride and other alkali ions along with boron as a flux and binder which allows low temperature sintering.

This helps to make capacitor cheaper but by the time one reachs 100c deflection in reliability is so much this is not even worth considering in equipment design. This all I tried to say.

About five years back when barium titanate fired thickness was shrinking from 1.4 micron fired to 0.9 micron fired to increase capacitance value in the capacitor people degraded X7R to X5R since resitance across was less than in withing the ceramic and ceramic started failing although starting ceramic was X7R and that is time I identified weak point in the capacitor constructuion and found a way to bring it back to X7R from X5R but I have not published and shared this with any of capacitor house if you like to know how to convert X5R forced degradation of X7R quality ceramic I can describe to you. I did and tested it and it works. This is identifying weak link in materials field use and then fixing that weak link to make it quality go back which material is capable

Lead titanates, zirconium titanates, and a couple of combinations are used. The real new materials for super caps are glassy 20 nm spherical particles. The material system is a titanate or zirconate. Some other lines of research are moving forward but you will have to wait for them.

Basic need is of highly polarizable oxide ceramics. Knowledge based has settled on Varium andstronitum titanates with dopants which covers all periodic table some for stablization like Niobium oxide and others other is to bring sintering temperature down like lithium borosilicate and other flux glass. and then other to control the expansion and reactivities like Magnesium oxide and others.

Basic arguments are still have bulk polarizable ceramic oxide and glassy is preferably over crystalline.

In glassy we need to control the micromolecule size that is other word for domain control so we can make super capacitor.

Super capacitor is nothing but individual ability of packing number of layer and how many pfarad it can hold as subassembly level or for poor word of choise on individual layer and ability to do thermal processing to make it cleaner from carbon and char which is carbon derivative and closer to graphite with different struture does not want come out at lower charge but have halytrail at higher power stoage device