Introduction to DKDP crystals
DKDP crystals are crystals with nonlinear optical properties that were typically grown by cooling in the past. However, due to the problem of two phases in the growth of DKDP crystals (the two phases here refer to two crystal phases, one belongs to the tetragonal structure, which is called the tetragonal variant and the other is the monoclinic structure, which is called the monoclinic variant), resulting in a cooling interval of 43 15, and the cooling space is narrow. As a result, more heavy water needs to be used, and the cost is higher. Before we understand the DKDP crystal growth research, we first need to know how to make crystals by solution, and only in this way can we better understand the growth process of DKDP crystals.
The general process of making crystals from a solution
Volatilization: A saturated or near-saturated solution is left to stand. Let the solution evaporate slowly so that the solute crystals condense.
Thermodifference method: A hot saturated solution is cooled slowly. As a result, the temperature is reduced, the solubility is reduced, and the solute crystallizes and condenses. (as is the approach used in this article).
Diffusion: A solvent (in which the solute is very soluble, but the whole is mixed as one) is slowly added to the surface of the original solution (forming stratification) and left to stand. The solvent diffuses slowly, and the solute crystallizes and condenses.
This is the operation process of three commonly used solution crystallization, and then I will explain in detail how the peristaltic pump is added to the DKDP crystal growth process.
A peristaltic pump was used to add the DKDP crystal growth process.
Concept: Using a Leffer speed-regulated peristaltic pump, the speed can be adjusted to keep the growth temperature of the DKDP crystal constant at 35. DKDP crystals are continuously produced through constant temperature.
Growth process: 1. Put the prepared DKDP solution with a saturation point of 40 into the flask, and keep the temperature of the DKDP solution at about 50 by heating it in a constant temperature electric heating bowl.
2. Use a peristaltic pump to slowly drop the DKDP solution in the flask into the growth chamber for the growth of DKDP crystals, here it is necessary to pay attention to the control of the flow rate of the peristaltic pump (you can also use the Leever flow type peristaltic pump to control, more functions), and wait until the DKDP solution in the grower reaches a certain volume, and then use another peristaltic pump (it is recommended to use the same model configuration as the first peristaltic pump) to transport the liquid in the grower to an Erlenmeyer flask. Take care to keep the volume of the solution in the grower constant at a certain value.
3. Prepare the solution in the Erlenmeyer flask into a DKDP solution with a saturation point of 40, pour it into the flask, and carry out the second cycle.
In this way, through continuous circulation, a large size of DKDP crystals can be produced with a small amount of heavy water, which greatly reduces the production cost, and DKDP crystals grow at a constant temperature, which overcomes the influence of temperature fluctuations on crystal quality, and achieves low cost and high output.
Note: Heavy water: The heavy water used in this article is a compound composed of deuterium and oxygen, also known as deuterium oxide, with the molecular formula D2O and a relative molecular weight of 200275, the relative molecular mass of specific water (H2O) 180153 is about 11% higher.