Fast Bolometric Response of Bulk La$\text{}_{0.7}$Sr$\text{}_{0.3}$MnO$\text{}_{3}$ Electroceramic Structures

We report on the performance of a microwave electroceramic bolometer of hybrid La$\text{}_{0.7}$Sr$\text{}_{0.3}$MnO$\text{}_{3}$/Al$\text{}_{2}$O$\text{}_{3}$ (0.2×2×4 mm$\text{}^{3}$) structure. The estimated thermal resistance of the bulk ceramic manganite film-single crystal sapphire interface is about 500 K/W at room temperature. This resistance is the main thermal barrier in the heat sink system and has been found to be slightly dependent on temperature. When compared with the high-T$\text{}_{c}$ superconducting bolometers, the La$\text{}_{0.7}$Sr$\text{}_{0.3}$MnO$\text{}_{3}$ microwave electroceramic bolometer works in a more wide temperature range, from 77 K to 330 K, excluding the narrow temperature interval at the metal-insulator phase transition (T=230 K). The microwave electroceramic bolometer sensitivity and the time constant at room temperature have been found to be 0.1 V/W and 100 ms, respectively. To improve the bolometer performance the point contact has been fabricated by a break junction technique. The optimization of a microwave electroceramic bolometer design brought to a considerable improvement of basic bolometer characteristics. The microwave sensitivity was about 0.3 V/W and the time constant was less than 100 ns.