Sample Preparation of Ferroelectric Crystals
Mentor:Timothy Usher, Professor of Physics, California State University San Bernardino
Ferroelectric materials are materials that remember the electric field applied to them. We use hysteresis loops to find the polarization of the crystal. Due to the many complications in getting a hysteresis loop, the best electrode arrangement to measure the organic ferroelectric materials is needed. The ferroelectric materials to be tested are croconic acid, diisopropylammonium bromide, and barium titanate. The current procedure is to measure the thickness of the materials being used in order to find the electric field. A laser displacement sensor and a micrometer are used to find the thickness. The crystals range in thickness from 240 to 1600 micrometers thick. Wire leads are applied to the crystal using silver paint, which acts as a glue and a conductor and then GE varnish is used as stress relief on the leads. A reoccurring issue is that the solvent in the silver paint along with solvents used for cleaning cause the crystal to dissolve. This creates a layer of nonconductive, nonferroelectric material between the crystal and the leads. Some solvents tested on diisopropylammonium bromide are chloroform, acetone, hexylene glycol, For some crystals, a very high electric field needs to be applied across it in order to get a hysteresis loop. However, the electric field may short the crystal. After the sample is prepared, a program called VISION is used to measure a hysteresis loops.