## 2 Materials and Methods  
The modified material PCR-13, which corresponded to the formula PbTi\({}_{0.512}\)Zr\({}_{0.385}\)Nb\({}_{0.093}\)Zn\({}_{0.006}\)Mn\({}_{0.004}\)O\({}_{3}\) (developed at the Research Institute of Physics SFU [13]), was used as the object of the research. The samples were obtained by a two-stage solid-phase synthesis, followed by sintering with conventional ceramic technology (CCT) with a variation in the sintering temperature (\(T_{sint. }\)) and with a Pb-containing backfilling. This was achieved by the hot pressing (HP) of small (\(\O 10\ \times\ 1\) mm) disks in the air atmosphere (laboratory technology, the HP-lab.) and hot pressing of large blocks (\(110\ \times\ 110\ \times\ 25\) mm, the HP-block) and in oxygen (HP + O\({}_{2}\)) [14]. In terms of specific technological procedures for each method, the synthesis--\(T_{synt._{1}}=\ 1140\) K, \(\tau_{synt._{1}}=6\) h, \(T_{synt._{2}}=1120\) K, \(\tau_{synt._{2}}=4\) h (for all methods); sintering: (CCT)-- \(T_{sint. }=(1500\ \div 1520)\) K, \(\tau_{sint. }=2\div 5\) h; (HP-lab.)--\(T_{sint. }=1450\) K, \(\tau_{sint. }=2\) h, \(P_{sint. }=200\) kg/cm\({}^{2}\); (HP-block)--\(T_{sint. }=1430\) K, \(\tau_{sint. }=2\) h, \(P_{sint. }=100\) kg/cm\({}^{2}\); (HP + O\({}_{2}\))-- \(T_{sint. }=1430\) K, \(\tau_{sint. }=2\) h, \(P_{sint. }=200\) kg/cm\({}^{2}\). The oxides of the following qualifications were used as starting reagents: PbO, ZrO\({}_{2}\), TiO\({}_{2}\), Nb\({}_{2}\)O\({}_{5}\), MnO\({}_{2}\)--\"c\" and ZnO--\"c.f.a.\" of the supplier in Rostov-on-Don LLC ROSTEKINOHIM (where \"c\" is clean,\" c.f.a.\" is clean for analysis). In order to avoid the lead losses associated with fusibility, volatility and consequently high diffuse activity of the lead oxide during the technological process, an excess amount (\((1\div 2)\) wt %) of PbO was additionally introduced into the material composition and a lead-containing atmosphere was created in the working chamber of the furnace due to the firing in the backfilling of the synthesized material. In addition, taking into account the possibility of the presence of a small (\(\sim\)1 wt %) amount of unreacted PbO in the charge, a two-stage synthesis with intermediate grinding of the reaction products and subsequent granulation of sintered powders provides a breakdown of the reaction product layer on the \"coated\" refractory particles (TiO\({}_{2}\), ZrO, Nb\({}_{2}\)O\({}_{5}\)) in addition to the homogenization of the composition. Thus, this allows the \"coating\" (PbO) reagent to access the unreacted volumes of the refractory low-active oxides. Preservation of the stoichiometry of a given composition of the material was also ensured by using finely dispersed raw materials (\(0.5\div 2.0\) um) that did not contain coarse fractions. This allowed us to significantly increase the reaction surface of the particles, to accelerate their diffusion and, as a consequence, to ensure the completeness of the reaction and prevent losses of lead. X-ray studies were performed by powder diffraction on a DRON-3 diffractometer using \(C_{OKa}\) radiation. The cell parameters were calculated in accordance with the standard procedure. The measurement error of the parameters was: \(\Delta a\ =\ \Delta b\ =\ \Delta c\ =\ \pm\ 0.003\ A\), \(\Delta V\ =\ \pm 0.05\ A^{3}\), where \(a\), \(b\) and c are the parameters, \(V\) is the volume of the tetragonal, \(T\), cell, \(\delta\) is a homogeneous strain parameter characterizing the value of the spontaneous strain, which is calculated from the formula for the \(T\) phase \(2/3\big{(}\frac{c}{a}-1\big{)}\)[15]. A scanning electron microscope JSM-6390L (JEOL Ltd., Tokyo, Japan) with a microanalyzer system from Oxford Instruments (Abingdon, UK) was used to study the microstructure of the samples of the chips.