Dependence of dielectric behaviour of Mn-Zn ferrite on sintering temperature

The dielectric constant of Mn-Zn ferrite was measured at different temperature and frequencies as a function of sintering temperature ranging from 1200°C to 1400°C at heating rate of 6°C/min. The resistivities as well as Seebeck coefficient were measured in the same range of temperature. More than one type of polarization is expected to vary the dielectric constant. Hoping mechanism was the predominant one in conduction processes. The grain size was calculated from X-rays and SE micrographs and it was found to decrease with increasing sintering temperature.     

Current enrollment characteristics of graduate students in psychology.

Presents some perspective on the general characteristics of graduate training in psychology provided by an assessment of data collected from the chairmen of 296 graduate programs by the American Psychological Association Educational Affairs Office as of October 1970. Almost 3/4 of the 23,859 students were enrolled in psychology departments proper and most of the others were in educational psychology programs. Size of programs varied considerably: 8 reported enrollment ranging above 300 (to a high of 924 students), whereas 46 programs enrolled 20 or fewer students. Most graduate psychology training took place in institutions that were public, large (10,000 or more students), and at middle levels of selectivity. Students were generally well dispersed regionally, although almost 1/2 of those in educational psychology were concentrated in the midwest. 60% of all programs reported some parttime enrollment. However, only 24% of the student population was on parttime study. 40% of all students were women, 4% were black, and 3% were from other backgrounds (Oriental and Spanish-American, primarily). Students in educational psychology (21% of the total enrollment) were somewhat distinctive in that larger proportion were women, nonwhite, or parttime students. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Electrical properties of carbon-doped KNO3 thin layers

A series of carbon-doped KNO₃ thin layers was grown from the melt by a special technique. The changes of the dielectric constant, d.c. resistivity, energy of vacancy formation, pyroelectric current and ferroelectric hysteresis loops with carbon concentration were investigated. The present study aims to clarify the effect of doping carbon as a conducting material on the properties of the dielectric KNO₃ thin layers by extensive use of experimental data from isomorphous sets of solid solutions of carbon and KNO₃. These systems were studied in the vicinity of the order-disorder phase transition region for various values of carbon concentrationx betweenx=0 andx=0.08. For the carbon doped layers, large changes in the electrical properties were found depending on the doped carbon concentration. The dielectric constant and d.c. resistivity were reduced appreciably, while the pyroelectric current showed improved behaviour in the presence of carbon, as compared with pure KNO₃ thin layers. Anomalous ferroelectric hysteresis loops were obtained in carbon-doped layers with a reduction of the ferroelectric loop temperature region by ca. 10° C at carbon concentrationx=0.07. The ferroelectric loops of the carbon-doped layers could be obtained x=0.06. Also, the energy of vacancy formation showed its minimum value of 0.45 eV atx=0.03 to 0.04. The marked change in the detailed character of the different electric properties of the doped layers during phase transition in the presence of carbon was interesting.