Single-crystal ferroelectrics and their application in light-valve display devices

Following a brief outline of the main display applications of single-crystal ferroelectric light valves, two categories of ferroelectric materials are distinguished--materials operated above their Curie temperature, which are electrically monostable, and materials operated below it, which are electrically bistable. Typical examples are KD
2
PO
4
in the first category and Bi
4
Ti
3
O
12
, Gd
2
(MoO
4
)
3
, and 5PbO:3GeO
2
in the second; in each case an examination is made of the physical properties of the material and the specific problems raised by the reading and the addressing of the display device using this material. To date the best results for display applications have been obtained using a single-crystal ferroelectric of the first category, KD
2
PO
4
, operated just above its Curie temperature.