The Growth of Berlinite (AlPO4) Single Crystals.
Abstract
Single crystals of the berlinite mineral phase of anhydrous aluminum orthophosphate have been grown for possible surface acoustic wave applications. The desired piezoelectric form of AlPO4 is the alpha-phase which is stable from 130 to 580 C. A seeded hydrothermal growth technique was used. Nutrient was prepared by heating hydrated alumina and phosphoric acid in a sealed silver liner from 140 to 200 C at a rate of 5 deg/day and a 15 deg temperature gradient. Because AlPO4 has retrograde solubility, the nutrient was placed in a silver mesh basket in the upper, cooler portion of the liner with the seeds situated in the lower, hotter portion. A 20% free area baffle separated the two regions. Two basic techniques were used for the growth runs. The constant temperature method with a 10 C gradient produced rates of 23-25 mils/day. The rates could be varied significantly depending on such parameters as growth temperature, gradient, nutrient basket mesh size, seed orientation and baffle design. The second technique used increasing temperature at a rate of 5 C/day over the range of 140-200 C to obtain average growth rates of 22-32 mils/day. Seed orientation for most runs was (0001) plates. New growth of AlPO4 for the most part was clear and of fair quality.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1980
- Accession Number
- ADA086751
Entities
People
- Larry E. Drafall
- Roger F. Belt