Influence of thermal cycling rate and sintering temperature of barium titanate and barium-strontium titanate ceramics on their dielectric properties

Ivan Mylnikov ¹ Alexander Semenov ¹ Alexander Anokhin ^1,2 Andrey Es’kov ² Yulia Pavlova ¹ Antonina Dedyk ¹ Andrei Kholkin ³

¹Department of Physics, Saint-Petersburg State Electrotechnical University, Saint Petersburg, Russia
²Laboratory “Materials and Structures for Electro- and Magnetocaloric Energy Conversion”, ITMO University, Saint Petersburg, Russia
³Department of Physics & CICECO-Aveiro Institute of Materials, University of Aveiro, Aveiro, Portugal

Hysteresis phenomena prevent the manufacturing of temperature control elements based on the electrocaloric effect, as well as active elements of microwave microelectronics [1]. Barium titanate (BT) and barium strontium titanate (BST) ceramics were fabricated. The effect of the temperature change rate in the "heating-cooling" mode and the sintering temperature on the temperature hysteresis ΔT_m has been studied. The measurements were carried out in the frequency range 100 Hz - 1 MHz. By ΔT_m is meant the temperature difference between the maxima of the dielectric permittivity during cooling and heating.

The temperature dependences on ε of ceramics with different Ba/Sr ratios, as well as with additions of magnesium and manganese, were measured. ΔT_m was significantly greater for BST with Mg and Mn than BST without additives. It was found that ΔT_m ceases to depend on the rate of thermal cycling at v ~ 0.05 K/s.

Figure 1 shows the dependence of ΔT_m on the Sr content (1-x).

Dependence of the phase transition temperature and ΔTm on the content of strontium in the BST solid solution

As the Sr content increases from 0 to ~ 0.3, the dependence is linear. With a further increase in the Sr content to 0.6, the temperature hysteresis remained at a minimum level of ~0.5 K.

The observed dispersion of the ε during the phase transition indicates the relaxor properties of the investigated ceramics [2]. An analysis of the temperature dependences using the modified Curie-Weiss law showed that with increasing sintering temperature, the relaxor properties of the phase transition become less pronounced.

Ceramic compositions containing Sr ~ 0.3 should be used to reduce the temperature hysteresis during thermal cycles at high speeds v ˃ 0.1 K/s.

1. Acosta M et al 2017 Appl. Phys. 4 041305

2. Patru R E et al 2020 Ceram. Int. 46 4180-4190